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Behaviors That Alter Your Genes to Improve Your Health & Performance | Dr. Melissa Ilardo
01:54:10
My guest is Dr. Melissa Ilardo, Ph.D., professor of biomedical informatics at the University of Utah.
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- [00:00]
Andrew Huberman
Welcome to the Huberman Lab podcast where we discuss science and science based tools for everyday life.
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Dr. Melissa Elardo
I'm Andrew Huberman and I'm a professor of Neurobiology and Ophthalmology at Stanford School of Medicine. My guest today is Dr. Melissa Elardo, professor of Biomedical Informatics at the University of Utah. Dr. Elardo is a world renowned expert in human genetics and epigenetics. She conducts pioneering studies on how our behavior and the environment can modify our gene expression. Today marks the first time on the Huberman Lab podcast that we really explore human genetics, epigenetics and how behavior shapes gene expression across generations. We talk about the inheritance of physical traits like eye color. And we dive deep into fascinating mechanisms such as the mammalian dive reflex, a physiological reaction to breath holding in cold water that, as Dr. Elardo explains, can dramatically alter the physiology of your spleen to allow significant increases in red blood cell count and oxygen availability to your brain and body. And by the way, the mammal dive reflex can be activated outside of free diving and you can even do it at home. We also explore how mate preference and selection in humans relates to the immune system. That is, if you were given a choice of many, many different mates, as most people are, the mate you would select is the mate who has the immune system composition that is most different from yours. And you would know that on the basis of their smell and how attractive their smell is to you compared to the smell of other people. We also talk about how differences in external traits signal important variations in organ function, hormone levels, and even brain physiology. Toward the end of our conversation, we discussed the current state and ethical considerations of gene editing in humans, something that's apt to be an increasingly important topic in the years to come because gene editing in humans is now possible and is happening. As you'll soon learn, Dr. Alardo does incredible real world experiments that reveal the remarkable interplay between genes and behavior. And she's an absolutely phenomenal teacher who makes complex genetic concepts accessible and practical. The conversation is sure to change the way that you think about mate selection, your parents, their parents, and what you can do to optimize your physiology and health through behavioral practices that influence gene expression. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science related tools to the general public. In keeping with that theme, this episode does include sponsors. And now for my discussion with Dr. Melissa Allardo.
- [02:36]
Andrew Huberman
Dr. Melissa Elardo, welcome. Thank you Nature versus nurture. Super big question that we all wonder about, you know, how much of our capabilities and potential and just general themes of life, everything from how we look to what we're capable of doing or not doing in the moment, or where we might be able to improve or not improve. We hear some of it's nature, some of it's nurture. So if we take a step back and we just ask a big question about human genetics, how much of our DNA is modifiable by our environment and what we do, what we choose to do in particular, because that's most of what we're going to emphasize today.
- [03:19]
Dr. Melissa Elardo
I think that's something we're still understanding at this point. I mean, I think every day we're getting more and more information about the ways that we can actually modify gene expression and these things that we thought were totally predetermined in the past. And so I think we're still learning with epigenetics and all of these new fields just how much we can actually change things. There are of course, things that are kind of written in our genes, but I think we're learning that there's a lot more that we can change.
- [03:45]
Andrew Huberman
Most of us at some point in high school, learn Mendelian genetics, Mendel the monk and his peas in his garden. Most people probably don't remember the details of that. But we also learn about eye color. You know, it, it's, you know, commonplace for people to understand that if both your parents have dark eyes, with very rare exception, it's unlikely that you're going to get light eyes as a child, but it's possible. But if you have one light eyed parent and one dark eyed parent, then you start to enter the probability game. And then at some point your parents dictate a lot of your appearance, your phenotype, and yet that there are aspects of our parents that are not seen in us at all and vice versa. And so I think for most people when we think about genes, we think about heritability. But your work focuses a lot on the aspects of genetic expression that are subject to change based on what people choose to do or are forced to do in order to survive. Something we call selection. So could you tell us about selection in terms of how quickly a given behavior, for example, can change our gene expression? I'm not aware of any way to change one's eye color without putting in like a colored contact lens. Now there's some esoteric things showing up online about people using these bizarre treatments to change their eye color. But for the most part, people accept that you're not going to change your eye color by behaving differently. But what are some examples where we can change our gene expression quickly, relatively quickly, by doing something differently?
- [05:20]
Dr. Melissa Elardo
Yeah, just going back to eye color because this is just one of my favorite genetics facts. So everyone with blue eyes descends from the same person. So at one point in human history, one person had a change in their eye color. And it's just like amazing to imagine this person who had blue eyes for the first time and then through many generations, probably because that was a very attractive and interesting feature in that individual you that spread throughout human populations as we know them. So I always just find that to be fun about blue eyes.
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Andrew Huberman
So there was a blue eyed F1 as we say.
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Dr. Melissa Elardo
That's right.
- [05:53]
Andrew Huberman
The first. Let's stay on eye color for a moment because before we get into how genes can be modified by behavior, I've been told that the green eye phenotype is one of the more rare eye colors. Is that true?
- [06:08]
Dr. Melissa Elardo
I think that's right. Yeah. I think it's the most rare.
- [06:10]
Andrew Huberman
Okay, so. And can we assume that there was an original F1 brown eyed person that gave rise to the entire lineage of brown eyes subsequently?
- [06:18]
Dr. Melissa Elardo
Yeah, I think in the history of humans as a species, I think that was our original eye color. And so then, yeah, having these other eye colors arise in the population created these events. I think green eyes, if I'm not mistaken, there were multiple people, you know, that comes from different genes from different individuals in the history of humans. But yeah, blue eyes is just this one individual.
- [06:39]
Andrew Huberman
I realize I'm slightly remiss on the statement about eye color not being subject to behavior. We know that as you get more sunlight exposure, in particular ultraviolet light exposure, that eyes will darken.
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Dr. Melissa Elardo
Is that right?
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Andrew Huberman
Regardless of where they start.
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Dr. Melissa Elardo
Interesting.
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Andrew Huberman
So like a blue eyed baby will have much bluer eyes at birth than it will at age 15, at age 80, for instance. And we believe that's due to changes in pigmentation because of of UV exposure.
- [07:04]
Dr. Melissa Elardo
That's really interesting.
- [07:07]
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- [08:21]
Andrew Huberman
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- [08:26]
Dr. Melissa Elardo
One of the best ways to ensure a great night's sleep is to make sure that the temperature of your sleeping environment is correct. And that's because in order to fall and stay deeply asleep, your body temperature actually has to drop by about 1 to 3 degrees.
- [08:38]
Andrew Huberman
And in order to wake up feeling.
- [08:39]
Dr. Melissa Elardo
Refreshed and energized, your body temperature actually.
- [08:42]
Andrew Huberman
Has to increase by about 1 to 3 degrees.
- [08:44]
Dr. Melissa Elardo
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- [08:55]
Andrew Huberman
The quality of my sleep.
- [08:57]
Dr. Melissa Elardo
Eight Sleep has just launched their latest model, the Pod 5, and the Pod 5 has several new important features. One of these new features is called Autopilot. AutoPilot is an AI engine that learns your sleep patterns to adjust the temperature of your sleeping environment across different sleep stages. It also elevates your head if you're snoring and it makes other shifts to optimize your sleep. The bass on the Pod 5 also has an integrated speaker that syncs to the Eight Sleep app and can play audio to support relaxation and recovery. The audio catalog includes several NSDR non sleep deep rest scripts that I worked on with eight Sleep to record. If you're not familiar, NSDR involves listening.
- [09:32]
Andrew Huberman
To an audio script that walks you.
- [09:34]
Dr. Melissa Elardo
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- [09:43]
Andrew Huberman
And this is great because while we.
- [09:44]
Dr. Melissa Elardo
Would all like to get to bed.
- [09:46]
Andrew Huberman
On time and get up After a.
- [09:47]
Dr. Melissa Elardo
Perfect night's sleep, oftentimes we get to bed a little late or later.
- [09:51]
Andrew Huberman
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- [09:52]
Dr. Melissa Elardo
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- [10:02]
Andrew Huberman
The middle of the night.
- [10:03]
Dr. Melissa Elardo
It's an extremely powerful tool that anyone.
- [10:05]
Andrew Huberman
Can benefit from the first time and every time. If you'd like to try Eight Sleep.
- [10:09]
Dr. Melissa Elardo
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- [10:24]
Andrew Huberman
Thank you for that. Because I think that most everyone is interested in eyes and eye color. What are the sort of examples that come to mind when you think of rapid changes in gene expression in any organ could be at the surface of the body or it could be internally that are governed by some change in behavior?
- [10:44]
Dr. Melissa Elardo
Yeah, so, I mean, our genes are constantly changing how they're expressing based on what environmental stimulus is coming in. So we have these changes that happen on the order of minutes or hours or things like that. Then there's also changes that we're finding out are happening over generation. We now know that there can be epigenetic changes. These are changes, little modifications to the genome that happen by molecules actually attaching to the genome and changing how genes express that can be passed down. This is really interesting from a. The perspective of things like trauma. You know, we know that, you know, refugee populations actually have some of these changes that they've inherited from their parents, even if they weren't, you know, victims of the. Of the event that caused them to be refugees.
- [11:30]
Andrew Huberman
Excuse me for interrupting, but are those changes that are passed down, are they adaptive? Are they making subsequent populations more resilient or less resilient?
- [11:37]
Dr. Melissa Elardo
Yeah, that's a very good question. You know, in the case of trauma and refugees, I'm not sure I do know in terms of starvation, that's been something that's been studied as well. So there was a famine that affected Dutch people several hundred years ago, I think, and that was actually also kind of recorded in these epigenetic changes. And so presumably that's a change that is helping that population to better survive that famine. So in that way, it's resilient. But then you think about in a contemporary situation where food is abundant, maybe that is no longer beneficial, even though at one Point it was then we have this other order of change, which is actual changes in the genes themselves that either arise from mutations in these single base pairs or at many different sites, or things like variation that's already present in the population at a certain amount that then increases in frequency throughout the population. This is where a lot of my work has focused. These are changes that until recently, we thought would take, you know, 5,000 years, 10,000 years at least. And now we're starting to understand that maybe that can happen in as short as 1,000 years, 2,000 years.
- [12:51]
Andrew Huberman
This might be slightly out of line with what we're talking about right now, but I'm really fascinated by this concept of hybrid vigor. I was taught, I don't know if the data still hold up, that if you give mice a choice of other mice to mate with, to produce offspring with, that they will select a mouse whose major histocompatibility complex, which is a reflection of diversity of immune genes, so to speak, they'll pick the mouse whose immune system is most different from theirs. Presumably the just so story, because we're making stuff up about why they do this, right? Nobody really knows. The just so story is that they do this in order to produce offspring that have a much broader array of immune genes to be able to combat a much broader array of potential pathogens. Is that true in mice still? And is it true in humans as well? Do people elect to produce offspring if given a choice, produce offspring with people that are more different from them as opposed to similar to them?
- [13:52]
Dr. Melissa Elardo
They did a very similar study in humans, and humans also are drawn to other humans that have these differences. So it's interesting, especially with the immune system. There was a study where I think they had people smell sweaty T shirts of members of the opposite sex if they were heterosexual, to see if how attracted they felt to the person just based on the smell of their sweaty T shirt. And people were more drawn to people who had very different immune systems than their own. So I think this is something. We see it in mice, and it's easy to say, oh, they're animals, of course they do that. But we do it as humans, too. It'd be interesting to know to what extent that's influencing our choice of mates and spouses.
- [14:35]
Andrew Huberman
Super interesting. So they're given a choice of sweaty clothing from the opposite sex, potential partner. I guess they're. I don't know if they were, you know, sent out on dates after the experiment, but they're. And they're smelling, let's say, ten different T shirts. That are sweaty and then they're saying. And then they rank order them and the one they like the most. If you go and look at the genome of the person whose sweat was.
- [14:57]
Dr. Melissa Elardo
On that clothing and specifically the immune system that you're talking about, you know, the. What is it? Histocompatibility complex.
- [15:03]
Andrew Huberman
Major histocompatibility complex.
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Dr. Melissa Elardo
Yeah. The more different they were in that, the more attracted they were to that smell.
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Andrew Huberman
It's kind of amazing, right? Like that smell, which we just think of as I like this body odor. I don't like this body odor. I love this. Body odor is kind of a proxy for gene expression related to the immune system of the offspring that you haven't even had yet with this smelly T shirt owner. It's kind of wild. So I think it speaks to smell. And these aren't really pheromone effects, but it speaks to smell as a pretty powerful driver of mate selection.
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Dr. Melissa Elardo
Yeah, I mean, I think it could be. It's also interesting, you know, we have, you know, when you're talking about hybrid compatibility or hybrid.
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Andrew Huberman
I called it hybrid vigor based on no particular knowledge of the correct term. I think it's the term I use because it's. Makes sense to me.
- [15:54]
Dr. Melissa Elardo
Yeah, yeah. Something like that. Something like that. You know, we're having with globalization, people meeting each other, you know, across cultures, across continents for the first time. So we're getting genetic combinations that have never been possible in the history of humans. And that's creating some interesting both kind of resilience and then also disease because you have, you know, combinations of genetic variants that have never been in the same individual before that are now showing up together.
- [16:21]
Andrew Huberman
I find this super interesting for a couple of reasons. First of all, I'll turn 50 in September, and I remember a time not that long ago where it was very unusual, for instance, to see an interracial couple in a television show when I was growing up. Now that's changed, right? And I think that's reflective of a number of things. I mean, there's cause and effect directionality here that we could get into. But that's a different podcast. But that, yes, people are intermarrying and or producing children with people whose backgrounds, genetic backgrounds are very different than their own. And if we take the opposite extreme, it makes perfect sense as to why this hybrid vigor thing would exist. And the opposite extreme is a very uncomfortable thing. But if you think about incest, incest has been discouraged in populations for a very long time without anyone understanding genetics, like the mechanisms of genetics Per se. It's been well understood that in small villages that people shouldn't mate with their siblings, shouldn't mate with their cousins, shouldn't mate, and ideally not even with second cousins because of the potential for disease. So I've always been fascinated by the idea that nature punishes, reproducing with people that are too close to you. And then of course, there's the moral and ethical and all that aspect, but mother Nature actually punishes individuals that do this through mutation.
- [17:46]
Dr. Melissa Elardo
Yeah. When you have two individuals who are closely related, that dramatically increases the chance that they're both carrying a variant that has a negative impact on the offspring. So when you have people kind of mixing more outside their families, then it's very likely that even if you're carrying this deleterious variation, it's going to be kind of watered down by outside genetic material. But as soon as you have people too closely related to each other, those things are ending up together and creating disease. Yeah. So it's definitely nature has a system built in that says, don't do that.
- [18:22]
Andrew Huberman
Yeah. I find it amazing that these things are operating below the level of conscious decision making to influence preference like this smell or that smell. Right. And we've established, you've told us that the smells that reflect the most distant immune system are the most attractive smells, which is really wild. So is it fair to say that humans are continuing to evolve, given that people are traveling further, meeting people from further away, having children with people from origin populations that presumably have never mixed before in the course of human evolution?
- [18:57]
Dr. Melissa Elardo
Yeah, absolutely. I think sometimes people kind of think, we're done, we've reached this ultimate point of evolution. It's, we've finished evolving. But as long as there are things that are affecting our ability to reproduce, we're going to continue to evolve. And you know, especially once you have this introduction of new genetic variation. I mean, some of the greatest adaptations in the history of humans have come from the introduction of new genetic material. So like the Tibetan high altitude adaptation is actually believed to have arisen from the crossing of humans with another early hominid group called Denisovans. So we essentially stole the advantageous genes from this other group. And so maybe you'll start to see that happening again as you have a more globalized population where different groups of humans are creating these interesting phenotypes through the mixing of their genes that maybe will lead us to be more resilient as our planet is changing around us.
- [19:56]
Andrew Huberman
How long ago did this gene that affords better abilities at altitude or ability to survive at altitude, enter the human population.
- [20:07]
Dr. Melissa Elardo
You know, I'm going to get myself in trouble because I don't remember exactly how long ago. More than 10,000 years ago. More than 10,000 Years ago. But it only became advantageous when the ancestral population of Tibetans moved into these extremely high altitudes. So they kind of, you know, was just sitting there waiting for a chance to be really advantageous. And then as soon as they went to these high altitudes, people carrying that genetic variation were at a huge advantage. And so they passed that along to their children and their children's children and so on.
- [20:37]
Andrew Huberman
So does that mean that at some point the species we know as Homo sapiens was able to reproduce with a species that was not Homo sapiens and that's how the gene entered the Homo sapien population?
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Dr. Melissa Elardo
That's exactly right. So, yeah, it happened. We see that happening with Neanderthals as well. But also this other population of, they call it archaic hominids, Denisovans. These are a population that were found in areas of Asia and their genes were introgressed, we say, so essentially inserted into the human genome. Individuals from that region tend to have a higher ancestry coming from that hominid group.
- [21:17]
Andrew Huberman
But that meant that a Homo sapien mated with this other species of primate.
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Dr. Melissa Elardo
Yes.
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Andrew Huberman
And the offspring had this gene incorporated into it.
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Dr. Melissa Elardo
Right, exactly.
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Andrew Huberman
And then that that offspring at some point mated with another Homo sapiens and so on and so forth.
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Dr. Melissa Elardo
Correct.
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Andrew Huberman
Okay. Yeah. I'm not trying to paint more color on it so that people. I'm not trying to be salacious here. I just. I think that sometimes we forget that in the primate lineage that there, there were other primates with whom Homo sapiens were capable of reproducing with.
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Dr. Melissa Elardo
That's right, yeah. And there's actually some extraordinary work from Svante Paabo, who works a lot with ancient DNA, where they found an individual who was a first generation mix, I think it might have been with Neanderthal, I forget now at this point, but. So it was a first generation, half human, half whatever archaic hominid it was, which shows you. I mean, if they found this, the chances that they would find this one mixed individual are so slim that it suggests that this was something that was actually happening a lot for them to happen to find it.
- [22:19]
Andrew Huberman
So in the diagram that everyone has seen of a quadruped animal, like walking on all fours and then gradually evolving into the upright form that we know as Homo sapiens, which is the primate right before it, which, by the way, being slightly hunched forward In a slightly C shaped position looks a lot more like Homo sapiens nowadays who are on their phones all the time. That's a separate point, that's an editorial point. But was there a kind of final primate step before Homo sapiens, Like one, or was it a collection of a bunch of different primate species? And then we got Homo sapiens.
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Dr. Melissa Elardo
Yeah, I mean, it definitely, you know, we have an ancestor. I don't remember exactly the name off the top of my head, but I have an issue with this diagram because it's, you know, it's the classic depiction of evolution. Right. But it really suggests, kind of like I was saying before, the. This trajectory and we are the pinnacle of it, we've achieved this thing. And I think it also fits with this concept of survival of the fittest, which I think is also a little bit misleading in that it's not about the most fit, it's about the best fit. So evolution doesn't care how fit you are in the way we think of fitness. It only cares how you fit with your environment. So the idea that evolution is driving any species, but especially ours, to towards some optimum, I think is inherently flawed.
- [23:43]
Andrew Huberman
I had a colleague at Harvard, he's still there, although I think he closed his lab, who once said it takes a lot of generations of offspring to evolve a given trait, but it takes very few to devolve a trait.
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Dr. Melissa Elardo
That's right.
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Andrew Huberman
Like you can create immense problems in all sorts of things, from pancreas function to mobility to vision with a deleterious mutation. But it takes a very long time to create an advantage for a given species through the accumulation of new combinations of genes. Is that true?
- [24:19]
Dr. Melissa Elardo
Yeah, yeah. I mean, it's. Most mutations are deleterious. Most mutations cause problems. And so we actually don't even see most mutations because they kill essentially the offspring before it even becomes a fetus. So most mutations are happening in a way where that we're not even seeing them. So to wait for something that comes up that's actually beneficial can take forever because you have to have exactly the right thing. The genome's huge. So when those changes are happening, for it to not only happen in the right place, but to not cause problems takes a really long time. So some of the faster examples that we know of evolution, especially in humans, come from when there's variation that's just already there and it's not particularly advantageous. Like I mentioned with Tibetans, until you move into a particular environment or until you start practicing a certain activity, like breath hold diving, we call it standing variation just. There's all these differences between all of us humans on Earth. And so when you have variation that's beneficial in the right environment, then evolution can happen a lot faster.
- [25:28]
Andrew Huberman
Got it. Okay. So I'm obsessed with the X Men. Yes, I love that series. I've probably watched it five different times. I mean, for a biologist who's interested in all animals, but the human animal, perhaps most, you know, it's, it's like the perfect form of entertainment for me. Right. Different individuals who have mutations that afford them specific gifts or abilities. But it creates some, let's just say some social tension between those that have and those that don't. And it's about learning these, to use these mutations for good versus evil. And it gets into all sorts of interesting human psychology. You work on the actual real life version of what I think of X Men and as you'll tell us today, women as well, which is, as you just told us, there's variation in all of our genomes. And occasionally, by virtue of the needs of a particular group or individual, those mutations afford them an incredible ability to do incredible things. So if you would, could you tell us about these underwater free divers that you've studied. This is a collection of studies, I realize, but maybe the first study because I find this to be one of the more incredible examples of, of behavior shaping what we think of are fixed properties of the human body. And please just tell us about it. It's such a wonderful story.
- [26:52]
Dr. Melissa Elardo
Yeah, absolutely. And I also love the X Men. Although if you ever want to ruin a perfectly good sci fi movie, watch it with an evolutionary biologist or noted. Yeah. So there are these incredible people, well, really all around the world. But I started my work in Indonesia called the Bajo. They are a group of what's called Ceno Mads. So Ceno Mads are. They're these people who spend their whole lives essentially at sea. Traditionally they live on houseboats and everything they need they get from the sea. And they do this through fishing, of course, and other things like that, but also through an incredible amount of breath hold diving. So they're extremely good at this. They can hold their breath for many minutes at a time. They dive to incredible depth. A lot of them wear these jewelry made of black coral. Black coral only starts growing at about 100ft deep, so that tells you how deep they're diving. So those are trophies they're actually meant for, to protect them from evil spirits and things like that.
- [27:51]
Andrew Huberman
How long are their breath holds on record? I've heard you Talk about this before, it's a little debatable, but the number I heard from you in a lecture, I went, whoa.
- [28:01]
Dr. Melissa Elardo
Yeah. So I was told, and I always emphasize that I was told I did not see this. I did not record it. I was told 13 minutes. And this was by the father of a diver who I worked with in Indonesia.
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Andrew Huberman
That's got to be in the neighborhood of world record stuff.
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Dr. Melissa Elardo
It is, yeah. I'm trying to remember what the current world record is, but it's also, I mean, you have to think about, if you see them diving, like, it's incredibly active. So a lot of the breath hold records that we think of are people floating in a pool. They're not moving, they're not expending any energy, they're not using up that oxygen as quickly. And these, these xenomads are, when they're underwater, they look like hunters. On land, they go deep enough that they're not floating anymore. And so they're walking on the. On the surface, you know, the. The bottom of the ocean with their spear guns and they. They look like hunters. It's incredible to see.
- [28:51]
Andrew Huberman
Amazing. So even if it's not 13 minutes, let's say it's half that, it's still super impressive.
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Dr. Melissa Elardo
It's very impressive. It's.
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Andrew Huberman
So do they grow up doing this?
- [28:59]
Dr. Melissa Elardo
They do, yeah. And they, in fact, they spend so much time traditionally on these houseboats and so little time on land that a lot of the children actually learn to swim before they learn how to walk. So one of the divers, when I was out there, one of my colleagues noticed that one of the diver's feet was very soft. And we realized that it's because he's never really walking. He's just always in the water. So his feet don't develop the same kind of calluses that ours do because he's not using them like we do.
- [29:26]
Andrew Huberman
Amazing. So how did you find this population and what sorts of questions did you start to ask?
- [29:31]
Dr. Melissa Elardo
Yeah, so I was actually diving as part of a coral genomics project in Thailand, escaping Danish winter, because that's where I was doing my PhD and I heard about a population called the Mokin. That's another group of these cenomads, and heard about their incredible underwater diving, started looking into it and saw a study that I think you've seen that, that showed that children, Mochan children, could actually see underwater better than European children, and started thinking about, you know, I mean, free diving is really dangerous. And so I was thinking that this could actually be something that's driving selection in this population that's causing this population to evolve.
- [30:10]
Andrew Huberman
In other words, just to put this in everyday terms for people, if you don't get good at this, you die.
- [30:16]
Dr. Melissa Elardo
Yeah, exactly.
- [30:16]
Andrew Huberman
If you die young enough, you don't reproduce.
- [30:19]
Dr. Melissa Elardo
Exactly.
- [30:19]
Andrew Huberman
If you get good enough at this point, you can live long enough to reproduce and your children will presumably inherit whatever mutation or genetic variants afford this ability.
- [30:32]
Dr. Melissa Elardo
Exactly. Yeah, yeah. And you know, I mean, we see with competitive breath hold divers, you know, I've never actually been to one of these competitions, but I've read about them. People pass out underwater all the time and they're, you know, pulled to the surface and revived. But if you're a sino mad diving in the middle of the ocean with no one nearby, nobody's going to pull you out of that water. And so you've just removed yourself from the gene pool completely. Whereas someone who maybe has a variation or has genetic variation that's making them safer at diving might survive that.
- [31:02]
Andrew Huberman
And in this case, the safety at diving comes from being able to stay under longer. We can talk about that. But as long as we're on this point and because some people will be tempted to go test their breath holding time, which. Please don't do it. I'm just going to do it across the board. Just don't do it. Learn from an expert. If you're going to learn to free dive, learn from somebody who's truly expert under the right conditions. I'll put a link to a couple folks I know that I have no business relation to Mark Healy and some other people that teach this on land first. Actually, you know what, I'll just tell you. You know what they told me was the first step in one of these free diving classes? I chose not to do it is to do not do this. But I was told, here's the first step. You're gonna hold your breath on land and force yourself to not breathe when the gasp reflex hits until you pass out.
- [31:48]
Dr. Melissa Elardo
Yes.
- [31:48]
Andrew Huberman
And I was like, you know what, I'm not gonna take this course.
- [31:51]
Dr. Melissa Elardo
Yeah. So this is exactly what gets people in trouble. Because, yeah, like, you know, we don't have a reliable sensor for when our, our oxygen is low. And so that happens to people underwater because that feeling that wanting to breathe is a buildup of carbon dioxide. And so, yeah, people teach themselves to overcome it like they're suggesting you do there. And then, you know, you're underwater and you pass out and that's it.
- [32:12]
Andrew Huberman
I've been told that you go from feeling that Gas reflex. You learn to ride that like a bump. The same way you might stay in a cold plunge or something a little bit longer than your impulse would have you stay in. But in this case, you're underwater, and then it passes, and then you're swimming freely about, and you're. You feel good. You're relaxed. You're doing slow exhales to let off that carbon dioxide, whatever carbon dioxide is left. And then it's just lights out. Yeah, that. There's no. There's no flickering. It just goes to complete blackout. Like curtains, as they call it. And then you're dead.
- [32:46]
Dr. Melissa Elardo
Yeah.
- [32:46]
Andrew Huberman
Unless somebody pulls you up to the surface.
- [32:47]
Dr. Melissa Elardo
Exactly. Yeah.
- [32:48]
Andrew Huberman
Yeah. So hopefully we sufficiently scared people into doing this. Okay, so this population, presumably, is not thinking about carbon dioxide thresholds for the gas reflex areas of the brain stem that are measuring carbon dioxide. They presumably learn through experience that if you do the right things, you live and reproduce, your family eats. You do the wrong things, you die.
- [33:08]
Dr. Melissa Elardo
Right, yeah. There's so much cultural knowledge that's integrated into the practice and that's passed on from, you know, generation to generation, because a lot of times they're doing this in family units. You know, one of the divers that I worked with, his dad used to be the most famous diver in the village. Now he's the most famous diver in the village. And. And so there's a lot of that tradition and that traditional knowledge that's passed on despite it. Maybe not looking like what we would read in a textbook.
- [33:32]
Andrew Huberman
When you say the. One of the most revered or expert divers. I'm very curious as to how this weaves back to an earlier part of our conversation. Is prowess at diving based on how long someone can stay under? And is prowess at diving because it correlates with the ability to secure resources? Is that somehow correlated with desirable mate? Do these people tend to have more offspring than people that are not as good at diving? And of course, there are confounds here. Like, you can imagine differences in hormone levels to begin with, eating more during puberty and growing, you know, stronger or whatever it is, or more or smarter? Not just smarter, but do you see this? Like, are the people who are great divers in the village, do they tend to be the ones with more children to be direct?
- [34:23]
Dr. Melissa Elardo
You know, it would be interesting to count that. I think now, you know, things are changing for the bajo, at least the community that I worked with, where a lot of people are moving away from traditional diving and into other kinds of fishing practices. And so I think at this point, this Prowess. This respect for these divers is more respect for the fact that they're keeping the tradition alive and they're continuing this tradition, even though it's a very hard thing to do. But, yeah, it would be really interesting. I know actually, the one diver came from a very big family, and that was something that the Bajau actually asked me about, was why do the Bajau have so many children? And so it would be interesting to see if, yeah, diving success correlates with reproductive success, because you could imagine that it would. I mean, they're diving for things that they're eating, so why wouldn't that increase your success on that?
- [35:11]
Andrew Huberman
Just out of curiosity and because I like seafood. What are they fishing for?
- [35:17]
Dr. Melissa Elardo
They dive for. It depends on where they are. They're spearing a lot of fish. Everything is delicious. They dive for shellfish. They also harvest seaweed sometimes and they actually collect a lot of sea cucumbers, which they dry out in the sun and then eat later.
- [35:33]
Andrew Huberman
It's like pure protein. Yeah, very interesting. So what did you study in this group?
- [35:39]
Dr. Melissa Elardo
Yeah, so we started thinking about, okay, for natural selection to act in this population, it needs some kind of physical trait to act on, which got us looking at the dive reflex or the mammalian dive reflex. This is if anyone. And again, I hesitate to tell people to do this, but if you hold your breath and put your face in a bowl full of cold water, your body responds as if you're diving. What that means is that your heart rate slows down, your blood vessels and your extremities constrict because your fingers will be okay with a little bit less oxygen, but your brain really needs that oxygen. So it's keeping the blood central where you need it the most. And then your spleen contracts. And so the spleen certainly wasn't the first organ that I thought about when thinking about diving. But the spleen is a reservoir. I mean, the spleen does many things, but one of the things that it does is it's a reservoir for red blood cells that are carrying oxygen. And so through that contraction, those oxygen rich red blood cells are now pushed into circulation and you get an oxygen boost.
- [36:41]
Andrew Huberman
How significant is that oxygen boost?
- [36:43]
Dr. Melissa Elardo
It's about 10% in most of us.
- [36:46]
Andrew Huberman
That's pretty impressive.
- [36:47]
Dr. Melissa Elardo
Exactly. Yeah. Yeah. I mean, it's enough to difference.
- [36:51]
Andrew Huberman
Yeah. By comparison. You know, there are a lot of discussions online about, you know, if you finish your exercise, resistance training or cardiovascular exercise with a brief sauna session. So going slightly hyperthermic. Right. This, you have to hydrate, et Cetera, but it actually works even better. As long as we're talking about dangerous practices, it works even better. If you're slightly dehydrated, do you get an overproduction of red blood cells in the supplement subsequent days. And this is used for a performance enhancing effect in elite athletes mainly. You have to again, avoid dehydration, death, et cetera. But this is done, and there are. Someone will correct me. But the shift in available oxygen is in the low percentages, like 1 or 2%. This is what people are fighting for using these kind of baroque protocols. You're Talking about a 10% increase in available oxygen through a contraction of the spleen. I didn't even know this. The spleen could contract.
- [37:44]
Dr. Melissa Elardo
Yeah, that's right.
- [37:46]
Andrew Huberman
Just when you put your face into colder than ambient temperature water.
- [37:51]
Dr. Melissa Elardo
Yeah. Usually in, like lab protocols, we do it at about 10 degrees Celsius or 50 degrees Fahrenheit, so quite a bit colder.
- [37:58]
Andrew Huberman
For how long?
- [38:00]
Dr. Melissa Elardo
Well, depends on how long you can hold your breath.
- [38:02]
Andrew Huberman
Oh, right.
- [38:03]
Dr. Melissa Elardo
Yeah. So, but you know, the extent to which, like, how long the contraction actually takes. I think we have room to learn more about that. But one thing that's slightly different from what you're talking about is that after you stop holding your breath, your spleen takes that oxygen back, essentially. So it refills with red blood cells, and that oxygen is that extra boost is no longer in circulation.
- [38:27]
Andrew Huberman
Ah, so it's only during the breath hold.
- [38:29]
Dr. Melissa Elardo
That's right. Only when you need it the most.
- [38:31]
Andrew Huberman
Interesting. What an incredible adaptation of the human body.
- [38:34]
Dr. Melissa Elardo
Yeah.
- [38:35]
Andrew Huberman
What are some other functions of the spleen? Just for. This is the first time the spleen has ever been discussed on this podcast, I think. Yeah, we don't think about spleens too often.
- [38:45]
Dr. Melissa Elardo
Well, you can live without one. So it seems like. How important could it be?
- [38:49]
Andrew Huberman
Well, for diagnosis for this population, it sounds like it might be critical. You'll tell us exactly. Yeah. What are some other things that it does?
- [38:56]
Dr. Melissa Elardo
It's involved in the immune response to certain bacteria. And actually now I'm trying to think of what else it does, but that's the main role is immunological.
- [39:06]
Andrew Huberman
One thing, in anticipation of this episode, I did a little reading about it, and it gets very heavy neural innervation, which is interesting. We don't normally think about our peripheral organs, besides our heart, as getting a lot of neural innervation. Of course, the gut has neural innervation, et cetera. But the spleen gets very heavy neural innervation, which makes me think that maybe there's the Opportunity for more, perhaps even conscious control of the spleen. Does this population communicate about any sense that they can switch this thing on, or is this just all kind of unconscious genius related to their behavior?
- [39:40]
Dr. Melissa Elardo
Yeah, as far as I know, it's all unconscious. It's not something that they talk about. And most of them, when I was explaining what the spleen was, it wasn't something that they had ever thought about or experienced any kind of sensation in the area where the spleen is found. But who knows? It's encapsulated in smooth muscle, I think, the spleen, and that's what controls that contraction. So, yeah, maybe there could be some way to, you know, to consciously contract your spleen. We also, our spleens contract when we exercise to a lesser extent. And this is why, like horses and apparently greyhounds, someone wrote to me after the study came out, have massive spleens, as do seals, who do a lot of deep diving. But that makes a little more sense.
- [40:21]
Andrew Huberman
Interesting. Horses. I don't. I don't think about horses being underwater very often.
- [40:25]
Dr. Melissa Elardo
Right.
- [40:26]
Andrew Huberman
Or greyhounds for that matter.
- [40:27]
Dr. Melissa Elardo
Yeah.
- [40:27]
Andrew Huberman
I wonder if they incorporate breath holds as a way to deploy red blood cells.
- [40:34]
Dr. Melissa Elardo
Yeah, it could be that. Yeah. It's something in the kind of breath holding aspect of extreme bouts of exercise is also contributing to that contraction, like.
- [40:45]
Andrew Huberman
When one becomes a bit hypoxic because you just can't keep up with whatever exertion. Like you just can't breathe in enough oxygen, dump enough carbon dioxide to keep up with your physical activity. Is there any. Is that one of the conditions under which it sort of mimics a breath hold or do you need this cold? There seems to be something about the face being cold.
- [41:07]
Dr. Melissa Elardo
Yeah, it's stimulation of the vagal nerve that is in part triggering this response which runs through your face. And so that's why the facial immersion is crucial to triggering the response. But there is, I think, a component of if you're just holding your breath where that also kind of triggers it. So. But yeah, it's really amazing to think that as mammals, this evolved sometime so long ago that it's in, it's even in mice. They've done a study where they actually trained mice to dive and they could measure the mammalian dive reflex in mice wild.
- [41:39]
Andrew Huberman
Yeah. So you sort of answered my next question, which was, why do we have a dive reflex? I mean, we're not a harp seal.
- [41:46]
Dr. Melissa Elardo
Right.
- [41:46]
Andrew Huberman
And we're not a diving bird. Why do we. Why do we have this?
- [41:51]
Dr. Melissa Elardo
Yeah, I mean, it's a great question. And I don't think we really know. There's a Some people talk about something called the aquatic ape hypothesis that says that one of our ancestors I'm trying.
- [42:01]
Andrew Huberman
Not to interrupt, but I just someone I've heard of the Stone Dape hypothesis. All the psychonauts love the stone Dape hypothesis, which is that psychedelics are what led to new ideas and daytime dreams that led to our evolution. And anyway, forgive me for interrupting. It was an interruption of of the stoned ape.
- [42:18]
Dr. Melissa Elardo
Yes, maybe the aquatic ape was right there alongside the stoned ape, but I think that given the fact that it's present throughout all mammals, I think it's much more likely that it was some very long ago ancestral proto mammal that was doing some kind of diving. And because of that, this response is present to varying degrees in all modern mammals.
- [42:43]
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Andrew Huberman
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Dr. Melissa Elardo
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Andrew Huberman
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Dr. Melissa Elardo
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Andrew Huberman
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Dr. Melissa Elardo
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Andrew Huberman
A free sample pack. I'm jumping around here, but I feel like these are the questions that are hopefully springing to people's minds here and there. I've seen these videos of babies being born into a swimming pool and they can and that you get on their belly, it looks like the Nirvana cover. And you know, they're, they seem perfectly happy to be underwater shortly after birth, which makes intuitive sense. They were in the womb. They were floating in the amniotic sack and they're underwater, so to speak. Do we come into this world knowing how to dive and be underwater because of our experience during pregnancy?
- [46:32]
Dr. Melissa Elardo
I mean, it seems like it. I mean I've seen, you know, if you take babies and not recommending anyone do this, but like blow in their face, you know, they instinctively hold their breath and can be put underwater. And actually Bajau people told me, and I don't know if this is something they actually do, but that the test of a bajo is as a baby, they pass the baby under the canoe and if the baby comes out the other side, then it's a bajo because it has held its breath like it will for the rest of its life.
- [46:58]
Andrew Huberman
What's the alternative?
- [46:59]
Dr. Melissa Elardo
Yeah, that's why I said I don't know if they actually do this, but it was just something that they told me. But yeah, I think there is some innate response where we know, even as babies to hold our breath.
- [47:11]
Andrew Huberman
It's fascinating. So what did you discover in this group of incredible divers?
- [47:16]
Dr. Melissa Elardo
So we discovered that they have larger spleens. So I mentioned the spleen's role in diving. It's increasing your. Sometimes people call it a biological scuba tank. It's increasing the amount of oxygen available to you. Our hypothesis was that they would have larger spleens because a larger spleen presumably means longer diving, safer diving. We compared them to a nearby population living in a very similar environment but with a history of farming. These are people who live right next to the ocean but aren't really interacting with it. Bajau children are in the water from the moment they're born almost. And then children in this other village didn't know how to swim. We found that compared to that village, the Bajau had significantly larger spleens. Their spleens were about 50% larger on average. This was true for divers and non diversity. So that showed us that it was very likely to be something genetic rather than the fact that you're diving increases the size of your spleen.
- [48:13]
Andrew Huberman
But does diving increase the size of the spleen?
- [48:16]
Dr. Melissa Elardo
This is a question that I think is still open because in both of the populations where I've measured this, divers and non divers have the same size spleen. However, other people have shown that if you train people, if you recruit people to a study and train them in breath hold diving, their spleens increase in size. I don't know if it's just that the populations that I've worked with have some kind of genetic factors that override that change. But yeah, open question, I would say.
- [48:46]
Andrew Huberman
I Know, you've done some work parsing which genes are different in this population and developing some animal models for that, and that some of this converges on thyroid hormone. Could you tell us the relationship between thyroid hormone levels that people are fascinated by thyroid hormone? It seems everyone either thinks they have a thyroid deficiency or an overproduction of thyroid, or they want to increase their thyroid. What is the relationship between thyroid hormone and spleen function as it relates to the production of these additional red blood cells?
- [49:16]
Dr. Melissa Elardo
The gene that we found that was evolving in the population correlates with higher than average thyroid hormone levels. So not like clinically hyperthyroid, but higher than average. And this is actually also true for Europeans who are carrying the same genetic variant. We showed in another group of individuals that if you have this gene variant, you have higher thyroid hormone levels and you have a larger spleen. It's not just something that's true in the senomabs. What we think is going on potentially, and this relates to the work that we did with mice as well, is that because of these higher, I hesitate to say elevated, because that's a clinical term, higher than average thyroid hormone levels, the mice, the humans, whoever it is, are producing more red blood cells. And so now whether that's kind of stretching the spleen, you know, because the spleens that we saw in the mice were larger but less dense, or, you know, if there's some other mechanism, we're not completely sure yet. But, yeah, it seems like these higher than average thyroid hormone levels, at least when the genetic cause was what we saw in the senomads, increase the size of the spleen, increase hemoglobin, increase hematocrit, increase red blood cell count.
- [50:26]
Andrew Huberman
I can think of two general scenarios where having a nice big spleen would be advantageous. One is in the performance enhancement context, your runner, maybe there's a way, I'm not suggesting this as a protocol that, you know, like getting your face into some cold water, holding your breath could afford you a kind of a boost. So instead of the scuba tank boost underwater, you're getting the above ground boost in endurance or strength output. But you said you have to be holding your breath at the same time in order to take advantage of that deployment of red blood cells, which is a little confusing to me because I imagine if the spleen contracts and the red blood cells are deployed into the body, that those are available, whether or not your mouth is open or not.
- [51:07]
Dr. Melissa Elardo
Yeah, yeah. And I don't think know how quickly the spleen reuptakes those red blood cells, but it does do that eventually. So maybe this is something that would be advantageous for short bursts or something like that. I mean, I think there's a lot of that. We don't know about the performance enhancing aspect of this, but that's really interesting because the work that we did in the mice where we replicated what we saw in these divers, they had larger spleens, they had higher red blood cell count, but they did not have any change in erythropoietin, which is how we normally think about changes in red blood cell count. This is a drug that was really popular with cyclists for a while. People would self dose with erythropoietin and it would increase. Increase their red blood cell count dramatically to improve their performance. So this is like an erythropoietin independent mechanism of increasing your red blood cell count that could have an advantage in performance, I think.
- [51:58]
Andrew Huberman
Fascinating. And then the other scenario is for robustness of one's immune system. I, for one, don't like being sick. And if there's anything I can do to increase the function of my immune system, including sleep, exercise, sunlight, all those things. But in particular, if I feel like I'm traveling an additional amount or not sleeping as well, I'd be willing to do pretty much anything within the realm of reason to improve my immune system vigor.
- [52:28]
Dr. Melissa Elardo
Yeah, absolutely.
- [52:29]
Andrew Huberman
And if sticking my face in a bowl of cold water 50 degrees for, I guess, as long as I can hold my breath in the morning is going to potentially afford that advantage, I'm willing to be the idiot that is doing this thing without any specific clinical trial yet. But I'd love to see a clinical trial on this.
- [52:47]
Dr. Melissa Elardo
Oh, absolutely.
- [52:48]
Andrew Huberman
Has anything been done to explore how that particular behavior that is generating the dive reflex can afford any enhancement in immune system function?
- [52:59]
Dr. Melissa Elardo
I haven't seen any studies that look at that. But it would be really interesting because, yeah, I mean, like you, I also would do anything to not get sick. And we do see in these populations a lot of older people who are continuing to dive. And there is a seeming health and robustness that I wonder if it's related to the activity of diving itself.
- [53:22]
Andrew Huberman
We have a family friend who's 94. My mom just told me 94. And my mom said over the phone, she swims four miles a day. And I'm like, there's no way. She goes, no, wait, she swims a mile a day, four days a week. Which is still pretty impressive.
- [53:35]
Dr. Melissa Elardo
Yeah, swimming a mile is. Yeah, that's quite impressive.
- [53:38]
Andrew Huberman
Four days a week.
- [53:38]
Dr. Melissa Elardo
Yeah.
- [53:39]
Andrew Huberman
At 94, presumably that's not backstroke. Some of it's. Yeah, I think like is there something to being in water that just generally is good for us?
- [53:50]
Dr. Melissa Elardo
I would imagine I shower, I bathe.
- [53:52]
Andrew Huberman
But you know, is there something good about swimming or floating or diving just for our general human physiology that we're aware of?
- [53:59]
Dr. Melissa Elardo
Yeah, I mean it's so low impact and such a natural way to, you know, to move, to exercise that. Yeah, I think especially as we age, it would be a really wonderful way to stay fit and healthy.
- [54:13]
Andrew Huberman
Has the size of spleens or rather the genes related to what you're talking about. Has that been correlated with whether or not people evolved from coastal versus more central regions of continents?
- [54:26]
Dr. Melissa Elardo
That's a really good question. We haven't looked at that. But it would be really interesting to see because I mean, you know, the oceans are an incredible resource in terms of food availability, especially to early humans. So you would imagine that anyone living near a coast anywhere would take advantage of this resource. So it would be interesting to see if maybe coastal populations are more likely to carry the genetic variation that enables this behavior. Although there are actually skeletons that have been found in various parts of the world near river systems that also suggest that those people have and diving. So maybe it's just being near water anywhere in the world.
- [55:00]
Andrew Huberman
I don't think of humans as an underwater species, but you're changing my view of this. I feel like we need to think about humans as some, some humans in the past and now spend a lot of time underwater without a scuba tank.
- [55:12]
Dr. Melissa Elardo
It seems to be that way. Yeah. All over the world.
- [55:16]
Andrew Huberman
That's super interesting. So this isn't the only population you've studied. If you would, could you tell us about the recent work the women study on women in particular and I'm very interested in how this relates to cardiovascular health.
- [55:34]
Dr. Melissa Elardo
Yeah. So you know, speaking of older divers, there's a group in Korea on an island called Jeju. These are all female divers. They're called the Haenyeo, which just means sea women. And the average age of the Haenyeo currently is around 70 years old. So. So that's when I think of robustness with age. I think of the haenyeo. But this all female diving population has likely been diving in that region for thousands of years. And what's really extraordinary about the Haenyeo, there's a few things. First of all, they're diving in extremely cold water, especially compared to the Bajau in Indonesia. No wetsuits no wetsuits. Well now they wear wetsuits. Up until the 80s they were diving in these cotton body suits that you can see provided zero thermal protection. I mean it's just cotton, cotton swimsuit essentially. So diving with no protection in extremely cold water. And as women they're diving throughout pregnancy. So they're diving up until the day they give birth sometimes and then they're back in the water a few days later. So this has really shaped this population in really interesting ways.
- [56:41]
Andrew Huberman
I was wondering, how deep do they dive into?
- [56:42]
Dr. Melissa Elardo
This is a really good question. I get asked a lot, how deep do any of these populations dive? And there's just like not really data. So we don't really know. You know, now we are starting to see, you know, we're looking at the Haenyeo. We actually tracked some of their diving and their dives tended to be much shallower, you know, not really going any deeper than 10 meters, 30ft, but, but they're also in their 70s, 80s even. You know, we had an 81 year old diver in our study.
- [57:07]
Andrew Huberman
30Ft is not nothing. We had a 24 foot deep deep end in the pool. I, you know, recreational pool near my home growing up. And when you're down at the bottom you feel significant pressure. You can let some air out to relieve some of that pressure but you're, I mean 20ft is 20ft, 30ft. And it's not a linear experience.
- [57:25]
Dr. Melissa Elardo
Yeah, right, exactly.
- [57:26]
Andrew Huberman
With every additional foot, like you're really experiencing more and more pressure. So.
- [57:30]
Dr. Melissa Elardo
Yeah, yeah, and I shouldn't say it like that. It's just that compared to, you know, the Bajo have been documented to dive deeper than 200ft deep.
- [57:37]
Andrew Huberman
Oh, I'm not countering. I was just, I just for sake of people out there who perhaps haven't spent time at the bottom of a pool, a 20 foot pool like 30ft is, is still really impressive.
- [57:47]
Dr. Melissa Elardo
It's very impressive. Yeah.
- [57:48]
Andrew Huberman
And, and, and they're bringing a fetus down that low.
- [57:51]
Dr. Melissa Elardo
Right. When they're, I mean, you know, again there's no documentation of how these women have been diving throughout their pregnancy other than, you know, we know that they were diving throughout their pregnancy, but yeah, presumably in their youth they were diving to these depths with their unborn child inside them. So it's a really, I mean when we think about natural selection and evolution, something that's able to act on a pregnant woman has the opportunity to take out two generations. If there's not genetic variation there, that's protective. So it's like if we want to talk about really fast examples of evolution, it's anything that's acting on pregnancy. And that's what we think has been happening in this particular population.
- [58:30]
Andrew Huberman
I have so many questions, some of which are cultural, some of which are biological. I'll start with the cultural questions. Why in this culture is it the women specifically that dive, are they revered and are they diving for a particular resource that is, well, because it's underwater, presumably is not available elsewhere. But what are they diving for?
- [58:52]
Dr. Melissa Elardo
We don't totally know. I have my own personal theory which actually relates to the fact that in a lot of places with cold water, so in Korea, in Patagonia, in aboriginal Tasmania, it's all women diving. So I suspect that there's something unique about the physiology of women that makes us better at diving in cold temperatures.
- [59:12]
Andrew Huberman
Or the men are afraid of the cold. I hear about a lot of guys that will spend dozens of hours picking apart deliberate cold exposure when it would take them a fraction of the amount of the time to get into the water. In my experience, this is not a controlled studies. Women are more tolerant of the cold, at least in terms of being willing to embrace it the first time around.
- [59:36]
Dr. Melissa Elardo
Interesting.
- [59:36]
Andrew Huberman
I have stories of, I won't say which countries. Elite special forces. It wasn't the US guys in that case, it was guys being terrified of getting into cold water, but otherwise being willing to do very, very challenging and indeed very dangerous things. I know a woman who first cold plunged 10 minutes. She was just in there. In my experience, women are more willing to get into the cold the first time. And then now there's a lot of debate online about cold tolerance in the two sexes, but the data aren't really solid there. So maybe the men are just afraid of going underwater.
- [60:13]
Dr. Melissa Elardo
It could be. These are some tough ladies. I will tell you that even into old age. My colleague Ju Young Lee at Seoul National University, she's been working with them for a very long time and she did a study where she was trying to find retired Haenyeo and the only ones she could find were over 100 years old because they basically don't retire, they just dive until they can't. Until they die, essentially. So she had these two women who were about 3ft tall who were retired haenyeo because those are the only ones.
- [60:42]
Andrew Huberman
She a hundred years old. As we have this conversation, I think it's very important to remind people that correlation is a causation. With all the obsession with longevity and living longer, I'm not going to rule out the possibility that getting into cold water, in particular diving, or generating the dive reflex with cold water doesn't have a longevity effect. But I don't think there's any direct evidence that it does.
- [61:03]
Dr. Melissa Elardo
No, no. And I mean it would certainly be interesting to explore, but I don't think there's any evidence so far other than anecdotal. Yeah.
- [61:11]
Andrew Huberman
The problem is that you need to do a very long study.
- [61:13]
Dr. Melissa Elardo
Right.
- [61:13]
Andrew Huberman
And the other problem with longevity studies is you don't really have a good control group, at least within subject, because you don't know when you would have died.
- [61:20]
Dr. Melissa Elardo
Right, Exactly. Yeah.
- [61:22]
Andrew Huberman
Okay. So these incredible women are diving up until their 70s, 80s, 70s, 80s beyond.
- [61:30]
Dr. Melissa Elardo
I guess the oldest diver that I've personally worked with was over 80. But yeah, they, and they, and they're, you know, I mean, they're so athletic as they do it. But yeah, in terms of, Are they revered? I think now, yes. I think that wasn't always true. When Haenyeo told me that in her youth she was kind of embarrassed to be Haenyeo. And a lot of it's because, you know, they're exposed to the sun, so they have darker skin than a lot of other women. They tend to be very loud because a lot of times they rupture their eardrums from diving. You know, if they don't pressurize correctly, you know, they can, they can have hearing damage. So they're known for being very loud. And so I think there was kind of a marginalization early on. But now they're recognized as a UNESCO World Heritage like intangible site essentially. And there's just, I think, tremendous respect for the population now.
- [62:22]
Andrew Huberman
Very cool. What are they gathering down there?
- [62:26]
Dr. Melissa Elardo
They are diving for all kinds of things. They're diving for sea urchin, abalone. They also harvest seaweed. I've seen them pull up octopus. They'll spear an octopus. And they do it in a very interesting kind of controlled way. Like they're really guardians of their marine environment where they make sure that they don't overfish things. So the sea urchin season is very short because if they over harvest the sea urchin, that population won't replenish. So they have this system where they really take care of the marine environment.
- [62:58]
Andrew Huberman
So it's all the proteins again, it's the expensive sushi. Unique. I'm still developing a taste for. I'm trying, but when it's, when it's.
- [63:06]
Dr. Melissa Elardo
Fresh out of the shell, there's nothing better.
- [63:09]
Andrew Huberman
I'm willing to try octopus I have too much an affinity for cephalopods to eat octopus, but I have in the past, and it can be delicious. And so it's amazing to me, if I step back from these two populations, and I think more broadly as well, about what people are willing to work for. Humans will work very hard to get protein. It's just kind of incredible how hard they'll work for proteins and lipids combined in delicious form.
- [63:40]
Dr. Melissa Elardo
Yeah.
- [63:41]
Andrew Huberman
I mean, we're not aquatic animals.
- [63:43]
Dr. Melissa Elardo
Right, Right.
- [63:44]
Andrew Huberman
And they're willing to risk their lives and the lives of their fetuses to the next generation. Right. There's nothing, I think, that a species tries to protect more than the next generation. One would hope, that they're willing to risk their lives on a daily basis, multiple times per day to go collect protein, basically.
- [64:02]
Dr. Melissa Elardo
Yeah. Yeah. And in these cold temperatures as well.
- [64:05]
Andrew Huberman
So do you think between on land hunting and what you're describing, that if we think about Homo sapien evolution generally, that a big part of Homo sapien evolution as it relates to selection of particular genes to drive particular traits and abilities, relates to this thing of just trying to get more protein and fat?
- [64:23]
Dr. Melissa Elardo
I mean, it certainly could. Diet is an incredible driver of selection. So, you know, a very common example of natural selection is lactase persistence. So our ability to continue to consume milk past infancy. And that happened very quickly in multiple different human populations. So it happened in Africa and it happened in Europe. And another example is the Greenlandic Inuit. A huge part of their diet was marine mammals that have really high lipid content. And so they actually evolved to be able to better metabolize those lipids so that it wouldn't kill them from heart disease or something like that. So, yeah, diet as a driver of selection is extremely strong. So it may be that this has been shaping our species in ways that we don't even know.
- [65:07]
Andrew Huberman
Super interesting. So in this group of Korean women, diversity. What's going on with their cardiovascular system? Earlier we were talking about how this might have implications for oxygen utilization in the brain and body and potential disease treatment ramifications.
- [65:27]
Dr. Melissa Elardo
Yeah. So we found two different adaptations. And I say adaptation, but there's kind of adaptation in a physiological sense, this thing that you can do by training, or adaptation in a genetic sense. And we have found one of each. So the training adaptation that we found was that I mentioned before, that when you dive, your heart rate slows down to try to conserve oxygen. So their heart rate through a lifetime of training slows down even more. So we could actually, you could. You could visually see this when they were doing these dives, we watching their heart rate, you could just see it plummeting. We had one individual whose heart rate dropped more than 40 beats per minute in less than 15. So really dramatic. And the reason that we think that that's a training adaptation rather than a genetic adaptation was that it was only true in the divers. So non divers with the same genetics didn't have this phenomenon. So that was, I mean that has, you know, it's interesting to think about how, what the potential health benefits of that could be. I mean it's clearly something that you can train. This has also been observed in other competitive breath hold diversity. But in terms of how that could benefit your health, I mean maybe it's good for your heart to have that kind of plasticity in terms of its response.
- [66:38]
Andrew Huberman
Yeah. When I think about heart rate, I think mainly about autonomic function. And again, vagal innervation seems to be a theme there, that the vagus is responsible for slowing the heart rate down. Anytime we exhale through, you know, respiratory sinus arrhythmia, we essentially slow our heart rate down. It's the fastest way I'm aware of to consciously slow our heart rate down. But so as one dives, I guess if they're exhaling like letting out some, some air, dumping some carbon dioxide, which is probably a good thing if you're a free diver. I don't want to encourage people to do this because that shuts off the gas reflex that would have you, you know, jolt to the surface. But assuming no one's going to go out and try this, by dumping air, you're, you're, you're exhaling. Exhaling slows the heart rate, but not 40 beats per minute. Yeah, it's usually a fraction of that.
- [67:25]
Dr. Melissa Elardo
Yeah. And so then we also found this genetic adaptation that we think is driven by the fact that they're diving through pregnancy. So when pregnant women have sleep apnea, which is where you hold your breath in your sleep, so it's kind of, you can think of it as unintentional diving through pregnancy. They tend to develop these blood pressure related complications. So like preeclampsia as they're just, they call them hypertensive disorders of pregnancy. And so we think that there's no studies that have shown this yet, but we think that you know, if you're diving same different kind of apnea through pregnancy, that would also increase your risk for these disorders. And so what we saw was that there was a genetic variant that was actually driving their, like a Lowering of their diastolic blood pressure while they were diving. And so we think that this is protective against these hypertensive or high blood pressure effects.
- [68:16]
Andrew Huberman
It's interesting. So for non divers, so for pregnant women on land who aren't from this population, the picture I'm getting is they're sleeping on their back perhaps because it's more comfortable as they get very pregnant and their airway is getting cut off at some point. So they're having these hypoxic episodes and then there's some gasping as the carbon dioxide gets high. This is also incidentally what people who are overweight or by the way, people with very big necks. This is why a lot of big necked, very lean men die in their sleep. This is a kind of well known thing in certain sports communities. It's very tragic. You say, well this person's fit, but they're lying on their back, they have big necks and their airway is compressed. You have a big neck, doesn't necessarily mean you're going to die early, but make sure you're breathing right at night because sleep apnea is very dangerous.
- [69:05]
Dr. Melissa Elardo
It is, yeah.
- [69:06]
Andrew Huberman
I think we think of it as just snoring.
- [69:07]
Dr. Melissa Elardo
Right.
- [69:08]
Andrew Huberman
But it's super dangerous.
- [69:10]
Dr. Melissa Elardo
You're putting yourself into a state of hypoxemia, so your oxygen is very low.
- [69:14]
Andrew Huberman
So for pregnant women who are concerned about hypoxia, what are the options that they have besides becoming a diver in this, joining this incredible community in Korea?
- [69:28]
Dr. Melissa Elardo
Yeah, I mean, I think, well, you know, that's one of the things that we're hoping to find from studying these women. So if they've evolved some kind of protective mechanism that protects them in the case of apnea, maybe that's something we could develop into a therapeutic that could be used to help prevent that same hypertensive disorder, pregnancy in pregnant women who have apnea for other reasons. But otherwise I would say I think preeclampsia used to be a death sentence for mothers and fetus, which is why it was such a strong driver of evolution. Now I think awareness of it enables treatment. But that's only something that's happened in the last, you know, I don't know how many decades. So that's why it was, it could have been such a powerful force in this population.
- [70:13]
Andrew Huberman
Uncomfortable topic, but I think an important one. Earlier you were talking about genetic selection and what determines survival of offspring. Is it the case that many miscarriages, if not most miscarriages are because the mutations that arise would have been destructive at some point postnatally after birth. So it's a kind of a nature's veto on the genetic program.
- [70:44]
Dr. Melissa Elardo
Yeah, I mean, I'm not a maternal health specialist, but I do know that most mutations create non viable embryos. And so, yeah, I think that could certainly be driving the early miscarriages especially.
- [70:59]
Andrew Huberman
So it could be pre implantation or post implantation, a mutation arises and somehow the genetic programs of embryology are somehow made aware that down the line this is going to lead to a stillborn fetus or something. So I mean, nature doesn't have a conscious logic in the same way that we think, but the, the genetic decision therefore is essentially a stop cell proliferation and the pregnancy is terminated.
- [71:31]
Dr. Melissa Elardo
Yeah, because I mean, a lot of proteins are involved in many, many systems. And so if you have a mutation that's problematic in one of those proteins that's involved in all these different systems, it's just going to start to go haywire very early on.
- [71:45]
Andrew Huberman
I'm very curious about how these genetic adaptations and how they relate to behavior impact organs versus things on the surface of the body that we can see, versus both. I don't know if this is true, but long ago I heard that, and I don't want to scare anyone because it's not true in every case. I'll repeat, it's not true in every case. But I was told by a friend of mine who's a physician that a lot of the wine spot pigmentation of the surface of the body like a baby will come out with a very dramatic like blind spot pigmentation of part of the face or the head sometimes, not always, is correlated with mutations in internal organs. And this is so. And this is having run a mouse lab for a long time, you study mouse mutants, mice that overexpress or lack or are hypomorphic for a particular gene. And you learn as you work with one of these populations that oftentimes the mutation that impacts, say retinal development, for which I need to take the retina out, look at it under a microscope and find which cells are miswired or something like that correlates with something on the surface of the body where you go, oh yeah, the ones with the curly tails, those are the ones that are likely to be the mutants. You still have to do the genotyping. You still got to send out DNA and you know, or analyze DNA. Nowadays you send it out. But in the old days we genotyped our own mice and what you find is that oftentimes there are these peripheral markers of central issues. I'm Also interested in the inverse of that, where there are peripheral markers of central advantages. So in these populations that you studied, they have these larger spleens or this ability to dive deeper and longer can overcome hypoxia through a drop in heart rate. Is there anything about their external appearance that isn't about soft feet or exposure to the sun that tells you like, this population is different? They look different in ways that we don't expect different populations to just look different. Does that make sense?
- [73:50]
Dr. Melissa Elardo
Yeah, absolutely. Yeah. And I mean, you know, to your point, like the phosphodiesterase that we found that was evolving in the bajo, phosphodiesterases are involved in so many different functions. And so there's, you know, there are chances for these mutations to affect not just the systems that we're interested in, but other systems as well. I mean, in both populations, the people look incredibly fit and athletic and they tend to have just a very robust appearance. Now is that because they're diving every day and there aren't that many 70 year old women who are jumping off a boat every day to go to work, or is it something related to their genetics? I don't think we know yet, but it would be really interesting to look into that more.
- [74:31]
Andrew Huberman
The reason I ask this is that as we were discussing at the beginning of today's conversation, mate selection, we think of they smell so great. We like them for this reason, we like them for that reason. And there's the conscious choices that we're making and then there's all the stuff working below our level of consciousness, like, oh, they smell great. And you're actually selecting at least in part for their immune system and the potential immune system of offspring. Even if you decide you never want to have children with this person for whatever reason, this stuff is happening in parallel, consciously and unconsciously. And so when I think about, you know, the, the ability, the special abilities of different populations at the level of internal organs, like a spleen ability, you also have to wonder if this is represented at the level of, you know, I don't know, like the, I mean, it could be anything, right? I mean, it could be the ones with the better spleens, have really nice hands. And you don't think about it, you don't think to correlate those things. But as in the example I was discussing with the mice in a laboratory, when you get mutations that, you know, impact an internal organ almost always, there's something about, you know, they might have a particular fur pigmentation pattern, assuming it's a Whole body mutation. Or sometimes they'll have like one web toe or they'll have pinkies, that. Pinkies. It's mice. They have a little, little back paw digit that faces in, not, not out like the others. And so you learn when you work with these things to say, those are the good ones, those are the mutant ones, or in some cases, those are the good mutant ones. Right. And I think as humans, we don't tend to do this consciously. It's not how we're trained to think, thank goodness. That would complicate all the dating apps. People would have to show their digits and Lord knows what else. But human mate selection is in part genetic selection. So what are your thoughts on this in terms of how these things correlate with human choice and behavior? I'm asking you to speculate here.
- [76:31]
Dr. Melissa Elardo
Obviously, I think that certainly, you know, I mean, we know that these populations have been evolving. We have theories as to what is driving that selection. But there, I mean, could be sexual selection. It could be like you're saying, like that people carrying this genetic variation that happens to also make them a good diver in ways that we expected to find, also make them more attractive in ways that we weren't even looking for. And you know, we weren't even thinking about pregnancy really when we started the study with the Haenyo. It wasn't until we got these results and we're saying, what is this difference in blood pressure? And speaking with maternal health specialists that we really pieced it together. So I think it's the kind of thing where, yeah, you just, you don't even really know necessarily all of the pieces of the puzzle. And that's where it's a lot more questions for us to ask in the future.
- [77:16]
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Andrew Huberman
And I should say by taking a.
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Dr. Melissa Elardo
Second function test, that approach worked. Comprehensive blood testing is vitally important. There's so many things related to your.
- [78:27]
Andrew Huberman
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- [78:29]
Dr. Melissa Elardo
Be detected in a blood test. The problem is, blood testing has always been very expensive and complicated. In contrast, I've been super impressed by function, simplicity, and at the level of cost, it is very affordable. As a consequence, I decided to join their scientific advisory board, and I'm thrilled that they're sponsoring the podcast. If you'd like to try function, you can go to functionhealth.com Huberman Function currently has a wait list of over 250,000 people, but they're offering early access to Huberman podcast listeners. Again, that's functionhealth.com huberman to get early access to function.
- [79:04]
Andrew Huberman
As long as we're talking about diving underwater, as a vision scientist, that's where my initial training was. I have to ask about vision underwater. Do these two populations use goggles now?
- [79:19]
Dr. Melissa Elardo
They do, but you can imagine goggles haven't been around that long. At some point in the past, they didn't. This was the study that first got me interested in. This was a study done in Moke and children, where I think it was literally a researcher who was on vacation in Thailand, noticed these little kids diving for things and having this ability to see underwater and set up an experiment and had European children and Mokan children diving to look at things underwater and that the Mokan children had better eyesight underwater than the European children. Now, that same researcher, after publishing this paper, went back to Europe and trained European children to do the same thing, essentially to perform at the same level as these Mocan children. And so there was this kind of dismissal, like, oh, well, you can train Europeans to see underwater just as well, so it must not be evolved, it must not be genetic. It has to just be training. But I think that's a logical fallacy that has stopped a lot of or has prevented a lot of research from being done in these populations. Because just because you can train someone to be at the same level as someone else doesn't mean that that person didn't have an advantage. And so I think that's yeah. I mean, definitely there's a difference in their vision. And what causes that, I think we still don't know.
- [80:35]
Andrew Huberman
So interesting. Just going to take one minute and explain to people the underwater thing, because I find it fascinating that the surface of the eye is rounded. Obviously people get that, and that's what allows you to refract, to bend the light to a single point point so that things look nice and crisp. And when you're underwater, the water essentially fills in the roundness around it. The air does, of course, above water as well. But because of the similarity and basically the density of the water and the surface of the eye, even though they're different, you get less of a bending of the light to a point. So the reason I'm saying this, the reason I'm giving this very crude lesson in optics, is there were really two possibilities. One is that kids that dive a lot in their youth have a flatter eye, right? If you think about a goggle or any kind of underwater seeing device, you're basically putting air between the eye and the water and you're making it flat. So the idea that the eye would become more flat through diving isn't inconceivable. I suppose it could happen, but it makes perfect sense to me as to why the European children could do this. Also, because you train it enough, it turns out it's the ability to constrict the pupil down really, really small that can account for this adaptation. This episode is brought to you by Enterprise Mobility. From fleet management to flexible truck rentals to technology solutions, Enterprise Mobility helps businesses find the right mobility solutions so they can find new opportunities. Because if your business is on the road, they want to make sure it's on the road to success. Enterprise Mobility moving you moves the world. Find your road@enterprise mobility.com so I wouldn't have thought that diving underwater and learning to pick up small objects underwater would make the eye more flat. Kind of like wearing a goggle underwater. But the point you make is an extremely important one because if you take a population that is already afforded some sort of potential genetic advantage and you train them even further, that's when you get X Men like behavior. And this is really all about the X Men, right? And women, as you clearly pointed out. And I think that brings us to this question of, like, human super performance. I think about the fact that almost always when I see a marathon winner nowadays, and I think about, is it Eliot Kachipki? Sorry. My, my, my. Normally I don't bring him into the the frame Consciously here, but for the audience here. But our, my producer and business partner at the Human Lab podcast is a triathlete. What is the guy's name? Elliot Kipchoge. Elliot Kipchoge set the marathon record with it with mild times on the order of 435, 26.3, 26.2 miles at somewhere in the 4 1/2 minute mile pace, continuously. Incredible. So he represents among the pinnacle of that sport. Almost always when we see these incredible endurance runners, they seem to descend from specific regions of the world. Can we talk about why that's so? Are they inheriting some sort of red blood cell trait? Is it the light bonededness combined with that, what leads to incredible human performance? I know you're a runner, your husband's a runner, so like, how much hope.
- [84:04]
Dr. Melissa Elardo
Is there for the rest of us?
- [84:06]
Andrew Huberman
And why is it that folks like Eliad are so unbelievably spectacular?
- [84:11]
Dr. Melissa Elardo
You know, I would love to look at that scientifically. He's absolutely incredible. I mean, breaking the two hour marathon record is also just unbelievable. But I think there have been, you know, I'm not as familiar with this literature, but there have been studies looking at the, the proportion of bone lengths in certain parts of Africa especially. It's also interesting to note that a lot of these really talented runners come from Ethiopia, where there are highland areas where humans have actually adapted to altitude. In addition to some of these biomechanical advantages, they may actually also have physiological advantages that enable them to run faster. But yeah, I think this is an excellent example of there's clearly something biological making people from this part of the world, you know, really excellent runners. And just because you can train a European runner to compete at nearly the same level, that doesn't mean that there's not something special about people like Kipchoge. And so, you know, this comes up a lot with the Bajau as well, because people say, oh, well, you know, they don't hold the free diving depth record. It's like, well, yeah, but they're not training to hold that record. You know, they're training, they're diving just to collect food for their families. They're not training. So what would happen if we did train them? And I think it's a great point.
- [85:29]
Andrew Huberman
If we take this out of the realm of physical performance and we take it into cognitive or mathematical performance, I feel like there's some fun thought experiments we could do. Before we started, you were talking about your time at Princeton as an undergraduate, seeing John Nash, famed for sadly having Schizophrenia, diagnosed schizophrenia, the topic of the movie Beautiful Mind with Russell Crowe. But at the same time having incredible abilities based on presumably things that either correlate with or just by chance run in parallel with the schizophrenia. Who knows what's driving what? Or if they're in parallel. We have examples, again, I'm pulling from movies like Rain man where there's a. A person has autism of a type that makes social interactions very challenging. But in that example, which is I think representative of at least some people with autism, extreme mathematical calculation abilities, especially in the physical space, being able to see things and count them very rapidly. Last example I'll give is there's this math competition held in India where the kids can update the numbers by moving their hands with a sensor on it and they're adding the numbers very fast. And you just see this kid basically spooling numbers, spooling numbers, spooling the numbers. At the end, they get one opportunity to answer the addition of this immensely long string of numbers correctly. And this kid nails it and you go, whoa. Like he's, he's adding things very fast, presumably through some training. But is it possible, is it within the realm of reality, based on what we know about human genetics, that there could be genes that select for, say, rapid updating of visual scenes combined with short term memory or whatever duration of memory is required that would afford certain people certain advantages in this based on inheritance. That's then combined with training, much in the same way that the ability of the spleen to expand if you dive a lot and you happen to be born in one of these communities that we've been talking about, is that possible?
- [87:42]
Dr. Melissa Elardo
Yeah, I mean, I think certainly. I mean, there's an interesting correlation between people in STEM fields and having family members with autism. I was actually at a lecture in Princeton where the professor asked the incoming class of students, how many of you have a family member with autism? And then of those, he had this, he displayed the statistics, how many of you are joining the engineering department? And it was much higher amongst engineers. And he explained that this can have to do with the fact that people on the spectrum tend to have an ability to hyper focus. And that actually makes you the ability to really narrow yourself to this one thing can make you a really good engineer in that way. It's a huge advantage because it's allowing you to succeed in that field, depending on obviously where you are on that spectrum and how that affects you in other ways. If that in some way is giving you an advantage, why wouldn't it be selected? For, of course, there are other ways that it could be a disadvantage. Oliver Sacks, I think, wrote about how people with Tourette's may have faster processing speeds. Again, maybe this is a place where that is advantageous, despite the other disadvantages that might come along with having that syndrome.
- [89:05]
Andrew Huberman
Huge Oliver Sacks fan here. I'm sort of becoming a historian of him, an informal historian. And he also loved to spend much of his time underwater.
- [89:13]
Dr. Melissa Elardo
Oh, did he? I didn't know that.
- [89:14]
Andrew Huberman
He was an avid diver and snorkeler and scuba diver. And I think in part he said because it's so quiet down there, incidentally, he had propozagnosia. He couldn't recognize faces. I think I have that right. I've known a few other people with that. And propystagnosia, the inability to recognize faces, also seems to correlate with this, for lack of a better way to put it, kind of nerdy, quirky phenotype. A former advisor of mine had this, although in part I thought he told us that, because then it gave him.
- [89:45]
Dr. Melissa Elardo
An out anytime he couldn't remember somebody's name the disorder.
- [89:48]
Andrew Huberman
Yeah, it's a great thing to put forward if you can't remember people's names. No disrespect to the actually clinically diagnosed people with proposagnosia. It gets you out of a lot of having to remember things. Yeah, I find this fascinating because in this day and age of pathologizing everything, it's interesting to take as you just did, and I really appreciate taking a step back and saying, yes, there are instances where people on the spectrum have they need assisted living their entire lives. But there are also people who are living incredibly productive lives, even making incredibly enormous, meaningful, and uniquely meaningful contributions to society, who we would say are probably on the spectrum. And so the question then becomes, to what extent is it genetic? To what extent are genes driving a proclivity for numbers or a proclivity for engineering? And on the opposite side, like, are great creatives, are they carrying a different set of genes, or are they just the ones that can't pay attention to anything, so they start throwing things together? That was a joke against the creatives.
- [90:52]
Dr. Melissa Elardo
It's interesting because it becomes a really difficult thing to test because how do you measure creativity in a way that you could then link to genetic information? So a lot of these kinds of understandings of genes come from things called genome wide association studies, where essentially they perform a correlation at every site in the genome to see which of these sites correlates statistically with whatever phenotype it is. So whether that's kidney disease or creativity, but you have to have a really good way of quantifying that trait. So creativity is nearly impossible to quantify something like mathematical ability. There's so many potential environmental nurture factors that could contribute to how that manifests in an individual that it also becomes quite difficult to quantify and therefore difficult to find any genetic factor that's contributing.
- [91:44]
Andrew Huberman
It's so interesting how we classify intelligence, you know, and some years back there was a lot of debate about, you know, IQ versus, you know, emotional intelligence. But there's this wonderful documentary, by the way, there's several movies by this title, but the one I'm thinking of is the documentary Spellbound, which is about the spelling bee competition. And it was the case for a long time that how well and how quickly kids could remember to spell certain words was thought of as some important correlate of intelligence, which is kind of crazy. And now in the day, an age of autocorrect and things like that. But one could argue that being able to spell is an interesting one, but that the different kids that they detail, one from a farming community, one from a community where the parents were really hard driving about academics. It tiles the entire representation of every kind of background you can imagine. Different types of parents, blue collar parents, highly educated parents, boys, girls, one that set that's clearly on the spectrum. And you see it in the family, you can see that and everything in between. And what you come to realize is that training effects are very real. Like if you take a kid in particular and you give them an activity and they repeat that activity, no surprise here, they get very good at that. But it also narrows the number of things that they can also be good at. This is what I think we forget about neuroplasticity is that the choice to get very good at one thing is also the choice to not get good at a bunch of other things. So when you step back, and I'm not going to ask you for parenting advice, but when you step back and you think about what you know about human genetics, is there a kind of a assuming one doesn't have to hunt for their food the way these populations you've been studying do, is there a kind of a optimal way to think about kind of genetic bias and what we perhaps should focus on? Or are you a equal opportunity, get after whatever interests you the most? Kind of.
- [93:40]
Dr. Melissa Elardo
I mean, you know, there's like companies where you can test yourself to find out what kind of athlete you should be. And I think that Kind of gets into something called genetic determinism, which is this idea that your genes determine everything about you, which we know isn't true. We know that it's a combination of, you know, genetic factors, environmental factors, all of these different things. But I think it's. It's interesting how much the idea that we're genetically predisposed to something or, you know, we're genetically better at something can actually influence how we are at that thing we talked a little bit before about. There was a study where they told people, they said, we're going to take your DNA, we're going to genotype you, we're going to find out whether if you train, you're going to get faster, or whether it's not going to affect you at all. They did that and they put people into these groups and then they tested them. After a few months, the people who they told were going to do better, did better. And this was like something they can measure at the biological level. They could measure specific molecules that had changed in that population of people compared to the other group of people. Now, the trick was that there was no difference genetically between these groups. It was just what they were told. So it's really interesting to think about. If you tell a child what they should or shouldn't do based on their genes, I think that's a really dangerous thing, or potentially you can motivate them through that.
- [95:04]
Andrew Huberman
So interesting. I mean, I think mindset effects are so important under discussed. I'm so glad this is coming up. Ali Crum was a guest on this podcast and she shared with us some incredible data on it. You tell people that stress is good for them, you stress them out, their health improves. You tell people stress is bad for them, you stress them out, their health gets worse, and on and on. There's just so many examples of these. Most of the time, people aren't taking a genetic test to determine whether or not they're likely to be good or bad at something. They're looking at their family photos or they're looking at their parents or their grandparents. This is the old version of genetic information. And I'm guessing here too, one should be very cautious. If your parents weren't athletes, does that mean that you don't have the genes to be a great athlete? Clearly, the answer is no. Likewise for intellectual pursuits.
- [95:58]
Dr. Melissa Elardo
We really have very little evidence that intelligence is heritable. So I think that's a big one. Especially, you know, if you feel like you're not coming from a very intelligent family. That doesn't Mean anything really, based on what we know currently.
- [96:14]
Andrew Huberman
What about rhythm and dancing ability?
- [96:16]
Dr. Melissa Elardo
Oh, man, I don't know. But I'll tell you, I did not inherit any rhythm from my dad.
- [96:22]
Andrew Huberman
I didn't inherit any rhythm from my dad or my mom. Although my dad is a bit more musical by virtue of being more mathematical. But that is not the same thing as dancing ability. I don't know if we have any truly bad dancers in our family, but we have at least one with exceptional rhythm and ability. She happens to be adopted. So there you go. That's a different version of genetic variation, and an important one in the sense that it's a cross fostering experiment, to put it in animal laboratory terms. If you don't mind, I'd like to talk about the ethics of genetics and genetic engineering. A few years back, a guy in China running a laboratory used CRISPR to modify the genome of babies. I believe he mutated the HIV receptor. I believe it wasn't to prevent them from contracting HIV under any circumstances, but rather the relationship between the HIV receptor and some things related to human memory. That was the speculation. There was very little known about this because this was happening in China in a kind of a closed format. It wasn't published in a peer reviewed journal. But he showed up at a human genetics meeting and he announced to the world that he had genetically modified babies through the use of genetic engineering. Now, on the backdrop of this, up until now we've basically been talking about genetic selection through partner selection, through all sorts of things, so that there are kind of indirect ways to genetically select. I think people forget that. But here we're talking about deliberate gene insertion or removal in embryos, creating genetically modified humans. After he did that, there was a sort of pause, as I recall. I was paying very close attention to this as to whether or not the international community of genetic ethicists and scientists would say, wow, this is potentially a feat of human engineering that could prevent disease, et cetera, et cetera. Or they were going to chastise him. And it turned out they chastised him. And as it were, we were told that he was actually put into prison. Now, whether or not that prison included a laboratory, we don't know, right? We have no idea. And there were a few other countries that chimed in and said, oh yeah, programs like this have actually been underway elsewhere for a long time. And then it just went silent. Right now the idea of the use of CRISPR to improve babies or to protect them against potential diseases is not commonplace. Or if it is, it's not discussed. What are your thoughts on the use of CRISPR to protect children from certain diseases? Let's just put it in that domain. And then of course, we could talk about the misuse of this. But, you know, you could think of parents who are maybe carrying a mutation they don't want their kids to have Huntington's, for instance, and you could potentially fix that gene. So I'm just going to cast all of that out there to give that kind of backdrop and get your thoughts. And there's clearly no right or wrong answer here, but this is very likely to be a big topic in the upcoming decade.
- [99:38]
Dr. Melissa Elardo
Yeah, it's a. I mean, it's a really great question, and I think one without, you know, a very good answer at this point. I think one of the, one of the things holding back this discussion up till now is that, you know, CRISPR is still a little bit of a blunt tool. You know, we're not, we haven't like the way that we're applying it isn't as precise as we'd like it to be to do the kind of gene editing that, you know, you would need to protect babies in the way that you're describing. And this is. There are things like off target effects, they say, so, you know, you're trying to edit one very specific part of the genome, but it ends up editing places that you didn't intend it to edit. So that's kind of one of the issues, I think, technologically that I think if I remember right, when that happened, people were a little bit like that. Technology isn't ready to be used in that way yet. But of course, that's something that is changing really rapidly. We're getting so much better at this. We're able to do it successfully in lab animals. And so, yeah, ethically, I think it's also interesting to think about enhancement versus correction. At what point? Where is the line between those two? If we're correcting some kind of genetic defect, first of all, some defects, other people might not even see them as defects. They might just see that as variation amongst humans. Where is the line between defects? Normal, enhanced. And so it's. Yeah, I don't know who would make those decisions once the technology is even available to apply that in unborn children. I mean, of course it would be a dream to prevent disease using these technologies, but it's a slippery slope maybe.
- [101:24]
Andrew Huberman
Yeah. There's a lot of debate right now online about some of these companies that allow for a deep sequencing of embryos, in particular in cases of IVF There's a company, I believe it's called Orchid up in the Bay Area, that's kind of foremost in this, where, you know, typically for IVF or even for natural pregnancy, there'll be an analysis of, like, is there trisomy, like, you know, extra chromosomes, which we know can lead to down syndrome, et cetera. But these companies, for a price, offer deep, deep sequencing of genes that correlate with. They're not causal in many cases, sometimes. Yes. But oftentimes correlate with, you know, potential spectrum phenotypes or, you know, things of that sort. Cancer susceptibility, BRCA mutation. Right. I know several people, unfortunately, that died from cancer and they carried BRCA mutations.
- [102:17]
Dr. Melissa Elardo
Right.
- [102:18]
Andrew Huberman
So there's a. This is real stuff. I think that the challenge for a lot of people is that as it stands now, it's very costly. So it sets up a scenario where wealthy people can afford to analyze embryos more vigorously than people who don't have the means to do it. But if we look back 10, 20, 30 years, getting your whole genome sequenced in the early 90s, was it when Venter and those guys first nailed that ability? Something like that. I'm thinking 90s sometimes. Okay, maybe I'm a little early. We're a little late on that one, but was extremely expensive. But now it's like, what, a hundred bucks or even free?
- [103:04]
Dr. Melissa Elardo
Yeah. Depending on the coverage. Yeah. You can sequence a genome for pretty cheap these days.
- [103:07]
Andrew Huberman
Yeah. So most technologies tend to advance that way. So it gets back to also this issue of how much information do you want? And so I guess given your training and understanding of human genetics, there's obviously no one size fits all answer. But when it comes to understanding how much control to exert over the genome, where do you land on this? I'm not trying to put you in the hot seat here. I think people are going to hear more about these technologies and just want to understand how to frame them. Them.
- [103:42]
Dr. Melissa Elardo
Yeah. Well, first of all, for context, I only have dogs, so I don't have to think about this in terms of human babies. But, yeah, I think, say you get your baby's genome sequenced and it's. It's going to. That baby is going to be blind. Is. Is that a problem? You know, a lot of blind people would say no. So, you know, it's. I think it's. It's such a personal question.
- [104:06]
Andrew Huberman
No, I think that's a great answer. I think it's a really hard question. Question to answer for any of us. But I Appreciate you being able to look at it and consider it. Dog genetics is fascinating there. The selection seems to be for phenotype, but also behavioral type.
- [104:22]
Dr. Melissa Elardo
Yes.
- [104:22]
Andrew Huberman
Which is fascinating.
- [104:23]
Dr. Melissa Elardo
Yeah. My fur babies were 100% selected to be cute.
- [104:27]
Andrew Huberman
That was the basis. It was the eye contact.
- [104:30]
Dr. Melissa Elardo
Yeah. I mean, actually literally one of my dogs is a type of dog that was bred to be a companion. So the only thing that they selected for was cuteness and companionship.
- [104:38]
Andrew Huberman
Is it the Bolognese?
- [104:39]
Dr. Melissa Elardo
Yes, that's right. Yeah.
- [104:40]
Andrew Huberman
There is a dog named after the spaghetti sauce or vice versa.
- [104:43]
Dr. Melissa Elardo
Yeah. Named after Bologna in Italy.
- [104:45]
Andrew Huberman
Oh, right. No, I was joking. Tell us, what is the breed of dog?
- [104:50]
Dr. Melissa Elardo
Bolognese.
- [104:51]
Andrew Huberman
And it's a mix between.
- [104:53]
Dr. Melissa Elardo
It's in the family of like, the Maltese Spichon, Cotone family. So these little fluffy white dogs that are in Renaissance paintings sitting in the laps of royalty.
- [105:04]
Andrew Huberman
It strikes me that whether or not we're talking about Mendel's peas in the garden, whether or not we're talking about dogs, whether or not we're talking about corn varieties or we're talking about humans, that for some reason we like to underestimate the power that genes in natural selection have. And behavioral selection, I guess, is the more appropriate term.
- [105:30]
Dr. Melissa Elardo
Right.
- [105:31]
Andrew Huberman
I'm very curious about this concept of admixing. If you could explain what admixing is. And what I'm getting at here is probably the biggest question for me, which is, are we all really one species? I mean, I like the idea that we are all one collective consciousness and unity and peace on Earth. Awesome. But really, in a serious sense, is Homo sapiens one species? I mean, there's a lot of genetic variation. And so if you could explain ad mixing, and if you're willing to go out on a limb and address whether or not there might be multiple species of primates walking around that we say, oh, that's a person, but they might be that much different than us. This episode is brought to you by Lifelock.
- [106:14]
Dr. Melissa Elardo
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Andrew Huberman
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Dr. Melissa Elardo
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- [106:38]
Andrew Huberman
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- [106:41]
Dr. Melissa Elardo
Yeah, so starting with admixture. Admixture is just when different ancestry populations mix. So it's kind of this relative term because, you know, if we're all descended from one ancestral population, then maybe we all have one ancestry. But I always like to put it in the context of myself. So my dad is 100% Italian. My mom's a mix of Northern European. I am an admixed individual. You know, if you think about it that way. And the reason that this is important in genetic studies is that if I claimed to be Italian and were included in a genetic study of Italians, the genetic variation that I have coming in from my mom's side would confuse that analysis. So admixture creates a ton of problems when we try to do genetic analyses. And so that's generally why we try to quantify it in genetics. But, yeah, when we're talking about it depends on kind of what scale, because I'm 100% European. So in that way, I'm not admixed if we're talking on the scale of continents. So it becomes kind of a blurry concept of admix depending on what level we're looking at. But as to your question of whether we are all one species, I would say I've actually. This is not the first time I've been asked this, especially given these. We call them superhuman populations. These people who have these extraordinary abilities, extraordinary physiology that makes them really good at what they do. I think the thing to keep in mind is that some of that variation can come from just a single base pair difference. I mean, a lot of times it's multiple genetic changes that create the differences between individuals. But, like, when you think about, you know, eye color, that's just one genetic variation or genetic variant in some cases, like the case of blue eyes, you know, so you could be exactly the same as someone else, except for this one change out of 3.5 billion. You know, so does that, like, at what point do we need enough genetic diversity to call a group of humans a different species? And I don't think that's something that we see anywhere on the planet that I know of.
- [108:45]
Andrew Huberman
Well, this has been incredibly illuminating. I've learned so much, and I know everyone listening has as well. I don't think we've ever had a discussion about these topics on this podcast in a solo episode or guest episode. You're truly the first person to come on here and talk about human genetics. And these incredible populations that you study are not only interesting in their own right, but they really shed light on the interplay between culture, selection, behavior, genetics, and basically what's possible in terms of human potential. And they also have important relevance to human disease, as you mentioned, with the hypoxia work. And it also shines light on something that I don't think we can get enough of, which is the incredible things that humans are capable of in these very different populations that grew up and continue to exist in ways that are so different than us. I think it can't help but turn the mirror on ourselves and ask ourselves, what are we doing in our daily lives behaviorally? How might that be impacting our genes, and to start to speculate about that in constructive ways. So I just really want to thank you for coming here today and sharing your knowledge, for the incredible work that you're doing. To be honest, I'm envious. If I were ever going to do a sabbatical, I don't think I'll ever have time to take the sabbatical that I've been accruing. But if I ever did, I'd love to study one of these incredible populations and try the free dive thing. It's really wonderful work and it's having a huge impact. It's in the news often as we'll put links to, and recently as well. I'm not going to ask you what you're onto now and what's coming next because we'll save that for a future installment, but just want to really extend my gratitude and on behalf of myself and all the listeners, thank you so much for the work you do and for educating us.
- [110:33]
Dr. Melissa Elardo
Thank you so much for having me and you're welcome in the field anytime.
- [110:35]
Andrew Huberman
Awesome. I'll take you up on that.
- [110:38]
Dr. Melissa Elardo
Thank you for joining me for Today's discussion with Dr. Melissa Allardo. To learn more about her work, please see the links in the show. Note Captions if you're learning from and or enjoying this podcast, please subscribe to our YouTube channel. That's a terrific zero cost way to support us. In addition, please follow the podcast by clicking the Follow button on both Spotify and Apple. And on both Spotify and Apple you can leave us up to a five star review and you can now leave us comments at both Spotify and Apple. Please also check out the sponsors mentioned at the beginning and throughout today's episode. That's the best way to support this podcast. If you have questions for me or comments about the podcast, or guests or topics that you'd like me to consider for the Huberman Lab podcast, please put those in the comment section on YouTube.
- [111:18]
Andrew Huberman
I do read all the comments.
- [111:20]
Dr. Melissa Elardo
For those of you that haven't heard, I have a new book coming out. It's my very first book. It's entitled An Operating Manual for the Human Body. This is a book that I've been working on for more than five years and that's based on more than 30 years of research and experience and it covers protocols for everything from sleep to exercise to stress control, protocols related to focus and motivation and of course I provide the scientific substantiation for the protocols and that are included. The book is now available by pre sale@protographsbook.com there you can find links to various vendors. You can pick the one that you like best. Again, the book is called Protocols An Operating Manual for the Human Body. And if you're not already following me on social media, I am Huberman Lab on all social media platforms. So that's Instagram X threads, Facebook and LinkedIn. And on all those platforms I discuss science and science related tools, some of which overlaps with the content of the Huberman Lab podcast, but much of which is distinct from the information on the Huberman Lab podcast. Again, it's Huberman Lab on all social media platforms and if you haven't already subscribed to our Neural Network newsletter the Neural Network Newsletter is a zero cost monthly newsletter that includes podcast summaries as well as what we call protocols in the form of one to three page PDFs that cover everything from how to optimize your sleep, how to optimize dopamine, deliberate cold exposure exposure. We have a foundational fitness protocol that covers cardiovascular training and resistance training. All of that is available completely zero cost. You Simply go to hubermanlab.com, go to the menu tab in the top right corner, scroll down to newsletter and enter your email. And I should emphasize that we do not share your email with anybody. Thank you once again for joining me for Today's discussion with Dr. Melissa Lardo. And last but certainly not least, thank you for your interest in signs.