How Your DNA Interacts With the World Around You (#246)

Summary

Episode Summary: How Your DNA Interacts With the World Around You (#246)

Podcast Information:

• Title: 3 Takeaways
• Host: Lynne Thoman
• Guest: Dalton Conley, Princeton Professor and Author of The Social Genome
• Release Date: April 22, 2025

In episode #246 of 3 Takeaways, host Lynne Thoman engages in a profound conversation with Princeton Professor Dalton Conley about the intricate relationship between our genetics and the environment. Drawing from his extensive research and his latest book, The Social Genome, Dalton challenges traditional perspectives on the nature versus nurture debate, offering nuanced insights into how our DNA interacts with the world around us to shape who we are.

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1. Introduction to the Nature vs. Nurture Debate

Lynne Thoman sets the stage by presenting the enduring question of what fundamentally defines us: our genes or our environment?

Lynne Thoman [00:02]: "For centuries, we've wrestled with the question of what makes us who we are. Is it our genes or our environment?"

She introduces Dalton Conley, highlighting his expertise in studying the combined role of genetics and environment in human development.

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2. The Complexity of Genetic Influence

Dalton Conley delves into the initial scientific optimism following the decoding of the human genome in 2003. Scientists anticipated that identifying specific genes would unravel the mysteries behind various traits and diseases. However, this optimism was met with unexpected complexity.

Dalton Conley [01:28]: "When scientists started decoding the human genome, many assumed the nature nurture debate was over and that soon we know the genetic blueprints for everything... But it wasn't that simple."

He explains that most traits, including chronic diseases like arthritis, schizophrenia, and heart disease, are highly polygenic—influenced by hundreds of genes rather than a single gene. This realization dashed hopes for straightforward gene-editing solutions or targeted pharmaceuticals.

Dalton Conley [02:08]: "Most things we care about... is highly polygenic, which means that it's not controlled by five or six genes, but it's controlled by hundreds of genes across the whole genome..."

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3. Understanding Gene Expression

The conversation shifts to gene expression, the process by which specific genes are activated or deactivated in different cells, leading to the diversity of cell types in the body despite having the same genetic blueprint.

Dalton Conley [03:08]: "Gene expression is the switching on and off of those genes in those particular cells that make a brain cell unique or different from a skin cell."

He emphasizes that gene expression is not binary but operates more like a dimmer switch, allowing for varying levels of gene activity influenced by environmental factors such as stress.

Dalton Conley [04:08]: "The environment comes under our skin and affects how our genes work."

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4. The Interplay Between Genes and Environment

Dalton introduces the concept of the polygenic index (PGI), a tool that predicts various outcomes based on an individual's genetic makeup. He outlines three primary ways genes and environment interact:

1. Genetic Influence Shaping the Environment:

   • Example: A child with genetic predisposition for sprinting is more likely to be selected for sports, receiving more training and opportunities.

     Dalton Conley [04:48]: "She's probably going to be picked first when they choose upsides in the schoolyard... her genes are going to have the effect of making her a Division 1 athlete."

2. Environmental Influence from Others' Genetics:

   • Our environment includes people whose genetics can affect us. For instance, marrying someone with a high polygenic index for depression can influence one's own likelihood of experiencing depression.

     Dalton Conley [06:12]: "The effect of your spouse's genes, depression, are a third almost as big as your own genes... in influencing your likelihood of depression."

3. Environmental Context Altering Genetic Impact:

   • Societal changes can modify how much genetics influence certain traits. For example, in a calorie-scarce environment, genetics might not predict weight as effectively as in a calorie-abundant, sedentary society.

     Dalton Conley [06:22]: "Genes didn't predict who was heavier or thinner... today... genetics predict where you fall in that distribution much more."

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5. Implications for Intelligence and Personality Traits

Addressing commonly held beliefs about intelligence and personality being solely intrinsic, Dalton compares the brain to an AI algorithm that requires environmental data to function optimally.

Dalton Conley [08:04]: "For something like intelligence, how that works is that the genes give your brain a machine learning algorithm... it needs to interact with the environment to come to fruition."

He highlights that the heritability of IQ increases from about 20% in early childhood to approximately 80% by age 35, demonstrating how environmental interactions amplify genetic influences over time.

Dalton Conley [08:04]: "The genetics blossom through more exposure to the environment... IQ ends up being about as heritable... as height."

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6. Parental Influence and Genetic Traits in Child Rearing

Dalton explores how parents might unconsciously cater to their children's genetic predispositions, impacting sibling dynamics and opportunities.

Dalton Conley [09:39]: "If one sister has perfect pitch, the parents invest more in her musical training, potentially neglecting the other siblings."

He also discusses the detrimental effects of genetic traits like skin tone, where siblings with darker skin might face more societal stress and discrimination, leading to health disparities such as increased hypertension.

Dalton Conley [10:23]: "The sibling born with darker skin is more likely to get hypertension... because they get more stress and discrimination."

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7. The Future of Genetic Prediction: A Genomic Revolution

Dalton warns of the rapid advancements in genetic prediction technologies and their potential societal impacts. He underscores the lack of public discourse surrounding these developments.

Dalton Conley [13:26]: "Genetic prediction is going to soon be taken up by insurance companies... IVF clinics... sperm and ova banks might use this genetic prediction algorithms to screen donors."

He calls for nuanced discussions on ethical considerations, emphasizing that genetic predictions are algorithms influenced by environmental contexts and are not deterministic blueprints.

Dalton Conley [13:26]: "We need to have a nuanced discussion of how genetic prediction should be and should not be used given that insight."

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8. Weighing Genetics and Environment

When asked about the relative importance of genetics versus environment, Dalton references a comprehensive review of twin studies spanning 50 years.

Dalton Conley [15:43]: "The average was 49% genetic and 51% environmental."

However, he critiques this simplistic division, advocating for an understanding that nature and nurture are intrinsically intertwined.

Dalton Conley [16:22]: "Nature versus nurture, and it's nature plus nurture. That really is how things operate."

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9. Dalton Conley's Three Key Takeaways

As the episode nears its conclusion, Dalton presents three pivotal insights derived from his research:

1. Genomic Prediction Revolution:

   • "There's a genomic prediction revolution happening as we speak... we should have a public debate about how we want to use genetic prediction in schools, in insurance companies, in fertility clinics, and so forth." ([16:27])

2. Genes as Dynamic Algorithms:

   • "We shouldn't think of genes as a blueprint. We should think of them as a greedy AI algorithm... the effect of the genes doesn't stop at our skin." ([16:27])

3. Integration of Nature and Nurture:

   • "We really can't separate out nature and nurture. We should just retire that 150-year-old debate nature versus nurture." ([16:27])

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10. Conclusion

The episode intricately weaves together scientific research and real-world implications, urging listeners to reconsider the binary view of genetics and environment. Dalton Conley's expertise illuminates the symbiotic relationship between our DNA and the world around us, emphasizing that understanding this interplay is crucial for making informed decisions in our personal lives and society at large.

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Notable Quotes with Timestamps:

• "When scientists started decoding the human genome, many assumed the nature nurture debate was over and that soon we know the genetic blueprints for everything... But it wasn't that simple." — Dalton Conley [01:28]

• "Gene expression is the switching on and off of those genes in those particular cells that make a brain cell unique or different from a skin cell." — Dalton Conley [03:08]

• "Genetic prediction is going to soon be taken up by insurance companies... IVF clinics... sperm and ova banks might use this genetic prediction algorithms to screen donors." — Dalton Conley [13:26]

• "We really can't separate out nature and nurture. We should just retire that 150-year-old debate nature versus nurture." — Dalton Conley [16:27]

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This episode serves as a compelling exploration of the dynamic relationship between our genetic makeup and the environments we inhabit, offering listeners a comprehensive understanding of how these factors collectively shape our identities and destinies.

Transcript

[Lynne Thoman]

For centuries, we've wrestled with the question of what makes us who we are. Is it our genes or our environment? Are we born with a set of traits that define us? Or is it the world around us that shapes the course of our lives? It turns out that it's not as simple as one or the other. What have we learned about nature versus nurture? And what makes us who we are? Hi, everyone, I'm Lynne Thoman, and this is three Takeaways. On three Takeaways, I talk with some of the world's best thinkers, business leaders, writers, politicians, newsmakers, and scientists. Each episode ends with three key takeaways to help us understand the world, and maybe even ourselves a little better. Today, I'm excited to be joined by Dalton Conley, a Princeton professor who studies the role of genes and and the environment. He's the author of the new book the Social Genome. I'm excited to rethink everything we thought we knew about the nature versus nurture debate and what makes us who we are. Welcome, Dalton, and thanks so much for joining three Takeaways today.

[Dalton Conley]

Thanks for having me, Lynn. My pleasure.

[Lynne Thoman]

It's my pleasure. Can you please read aloud a great quote of yours?

[Dalton Conley]

Sure. When scientists started decoding the human genome, many assumed the nature nurture debate was over and that soon we know the genetic blueprints for everything. Obesity, intelligence, susceptibility to chronic disease, even individual personality traits. Pharmaceutical companies would develop drugs that could target the handful of genes responsible for, say, arthritis or heart disease or schizophrenia. The end of illness would soon be at hand. But it wasn't that simple.

[Lynne Thoman]

So, Dalton, why wasn't it that simple? Is there one gene for arthritis or heart disease or schizophrenia?

[Dalton Conley]

No, there's no one gene for any of those chronic diseases that affect so many Americans. In fact, there's not even a handful of genes, much to the chagrin of the scientists who had first worked on the Human Genome Project. In a few short years after the human genome was decoded in 2003, we learned a hard lesson, which is most things we care about, everything from height to schizophrenia to arthritis to heart disease, you name it, is highly polygenic, which means that it's not controlled by five or six genes, but it's controlled by hundreds of genes across the whole genome in thousands of locations in your chromosomes. That was a huge disappointment because that meant that you couldn't easily just gene, edit or develop a pharmaceutical to knock down or enhance a handful of genes to fix the problem.

[Lynne Thoman]

And even the genes don't tell the whole story. Can you Explain gene expression, what it is and how it works.

[Dalton Conley]

When the human genome was decoded, there was a betting pool to how many genes are humans going to have. Lowly corn has 100,000 genes. It turned out that we had only 20,000 genes, which nobody was even close. And what that means is that those 20,000 genes are doing a lot of work. In every cell in your body, you have the exact same blueprint, but your skin cells are obviously very different than your liver cells and your brain cells. So gene expression is the switching on and off of those genes in those particular cells that make a brain cell unique or different from a skin cell. Those switches, the gene expression are also affected by the environment, which is a very exciting area of research as well. So if you have a lot of stress in your life, genes for cortisol receptors are going to be switched off, for example, because you've had too much stress for too long. So yes, it's a way that the environment comes under our skin and affects how our genes work.

[Lynne Thoman]

But it's not just the genes that we actually have, it's which genes are turned off, which or turned on.

[Dalton Conley]

Exactly. It's usually not an on off switch, I should say it's more like a dimmer. But in certain cells or in certain conditions, certain times of life, you'll produce more of this gene's protein or less of it. It's usually not just completely off or completely on.

[Lynne Thoman]

Hmm. So interesting. We often think of our genes in our environment as separate forces, but you believe they're actually intertwined and that there's a feedback loop. How does that work? And can you give an example? I love your example of the sprinter.

[Dalton Conley]

Biologists have known that you can't talk about genes independently of the environment or the environment independently of genes. But what's really exciting as of late is that we now have tools because we've measured the whole human genome and we have a lot of data that we didn't have before that measures millions of people's genomes. We can construct these polygenic scores that predict outcomes like schizophrenia, educational attainment, height, body mass index, you name it. There's a polygenic index for it that is a tool for which us to see how genes and environment interact. And genes and environment interact in three ways. And the first is, I'll give the example that you mentioned is imagine a kid that's born with two working copies of the sprinters gene, the fast twitch muscle gene that almost all elite athletes have. She's going to probably be picked first when they choose upsides in the schoolyard. She's probably going to win all the games of tag or races in school. Maybe she's going to be spotted and picked to go into organized sports and she's going to excel there. All that exposure, all that environment of getting chosen to be on an organized sports team, getting more investment in terms of summer camps and training, that's environment. But it's a result of her genes, and it's a mechanism by which her genes are going to have the effect of making her, let's say, a Division 1 athlete when she gets to knowledge. A second aspect of how genes and environment are kind of indistinguishable is that the environments we encounter, your parents, of course, your siblings, your peers at school, your co workers, they all matter to how you turn out or, you know, how you behave or your health. But they're partly made up of the genes inside their bodies. We can show that, for example, if you marry somebody with high polygenic index for depression, that affects your likelihood of becoming depressed. In fact, the effect of your spouse's genes, depression, are a third almost as big as your own genes inside your body in terms of influencing your likelihood of depression. The genes of your classmates at school affect your likelihood of smoking almost as much as your own genes do. I call that the social genome or the environment is really genetics one degree removed to some extent. And then the third way is that when there are massive environmental shifts, genes can matter more or less. So in the early 20th century, calories were scarcer, physical labor was more routine for most of us, and obesity was pretty rare. And genes didn't predict who was heavier or thinner. But fast forward today in our like calorie abundant world and our more sedentary lifestyle, and the population is heavier, the distribution of weights is wider, and it turns out that genetics predict where you fall in that distribution much more than they did before. So those are the three ways genes create the environment they want or need, so to speak. The environment is in part genetics one degree removed. It's the genes of the other people around you affecting you. And third, the environmental landscape influences how much genes matter or don't matter.

[Lynne Thoman]

How does this apply to intelligence or personality traits that are often considered intrinsic.

[Dalton Conley]

For something like intelligence, how that works is that the genes give your brain a machine learning algorithm, like an AI algorithm. It says, go out and get data, train this algorithm on data and it'll refine this algorithm. And we see that happen in that the genetic influence on IQ is very low in early childhood. It's like about 20% and it rises to about 80% by age 35. So the genetics blossom through more exposure to the environment, more feedback in interaction, asking questions in school, choosing harder classes, reading more, getting more information, training your mind. All the genes give you is a, like I said, an algorithm for interacting with the world. And that second step of the interacting with the environment is really crucial for IQ to become genetic. So ironically as you get older and more experienced of the environment, the random aspects of the environment matter less and your genes selecting your environmental inputs and interactions matter more. And IQ ends up being about as heritable, meaning as genetically determined as height. But it's a very different pathway to get to that 80 or so percent. Your genics alone, just inside your brain or inside your skin aren't going to be determinative. They need to interact with the environment to come to fruition.

[Lynne Thoman]

So parents might unknowingly treat their children differently based on their kids genetic traits. Can you give some examples of how that plays out and what impact it has?

[Dalton Conley]

So imagine two sisters, that one is born with perfect pitch, the other is not. And that's a genetic highly genetically influenced trait. The parents are just going to invest more in the kid with perfect pitch in terms of musical training. The kid without perfect pitch is not going to want even to go to a musical summer camp or go to conservatory because it's not fun to do something you stink at. It is fun to get positive reinforcement and that's happening within the family. It's going to happen in the wilder world. That would be a rational example of gene environment interplay. Like if you have the nate talent for something you get more investment. But you know, it might be that there's a third sister and she has perfect pitch too, but she's not as attractive as the first sister who has perfect pitch. And she gets less attention, less investment from her parents. They even think that she doesn't quite sound as good. And that's unconscious bias based on her looks which are genetically determined as well. Another example of how this can be kind of pernicious sometimes is a study we did looked at African American siblings and we looked at whether or not one was born with lighter or darker skin than the other. And we found that the sibling born with darker skin is more likely to get hypertension than the one with lighter skin. Presumably because they get more stress and discrimination. They're treated differently based on their skin tone in genetic effects can work in all sorts of ways. Skin tone is controlled by your genes, eye color is controlled by your genes and people react to you differently based on those physical characteristics. So it doesn't have to be necessarily a sprinter getting good training because of their talent. It can be something like that as well, unfortunately.

[Lynne Thoman]

As the parent of school aged children, how has your own perspective on raising children changed now that you understand the interplay between genes and the environment so deeply?

[Dalton Conley]

I have two older children that are adults now and I raised them before I really knew the power of genes. And I thought that I had a lot more power over how they were going to turn out than I did. I recognized that as a parent you're not in control, you're being parented by your kids genes at least as much as you're parenting them. But then I had a third kid 20 years later and I was in the thrall of genetics at that point. We were doing IVF to conceive him and I thought of wow, we could optimize know among the embryos we could choose the one with the highest polygenic scores for certain traits or the lowest for other traits. What about that? We turned out not to do that and I'm of course glad we didn't because I'm really, I love the kid we got by chance. And I also now realize that using that kind of simple genetic prediction idea ignores the fact that we've been talking about gene and environment are braided together. And I can control the environment of my child a little bit in response to their genes. So to give an example example of that, if I found out that my son had a musical talent, which would be quite a shock to me because I have zero, I would expose him to instruments and to lessons from a young age and see if they took and could start that forward feeding snowball. If he had tested to be off the charts for the PGI for opioid addiction, I would try to make sure that if he breaks his arm or if he has a surgery, he's not prescribed opioids as a painkiller after that, or that he's aware of that as he gets older and makes his own medical decisions.

[Lynne Thoman]

If there's one thing that you want people to understand from your research, what would it be and how can we use this knowledge to make better choices in each of our own lives?

[Dalton Conley]

One of the important things I'd like to sound the alarm on is this genetic genomic revolution that's happening right now under our doses in the last 15 years, this new tool I mentioned, the polygenic index, has come on the scene and it's become more and more predictive of outcomes. They're still in their infancy, they're noisy, they predict poorly, but they're getting better every year and they're going to radically transform society. We have a lot of talk about the promise and perils of AI. We've had a lot of public discussion about CRISPR gene editing as a potential revolutionary technology. But I think the polygenic index is just as revolutionary as those other two and is here already. Genetic prediction is going to soon be taken up by insurance companies. Like if you want to apply for a life insurance policy or a long term care insurance or even car insurance, they might soon ask for a swab of your cheek, a saliva sample or a blood spot and analyze your DNA to make better pricing of your premiums. Are people okay with that? IVF clinics. Some IVF clinics already offer what I had thought I wanted seven or eight years ago. The polygenic screening for embryos to select which one you want to implant. So people are going to be optimizing babies long before there's going to be genetically modified babies running around preschools. Sperm and ova banks might use this genetic prediction algorithms to screen donors or to offer clients different samples based on their price point of how good a genetic sample they want. That's just a few of the examples of how this area of genetic prediction is going to sweep across society. And we have had no discussion about it. I think we should keep in mind it's not a blueprint, it's an algorithm. And it depends on the environment and the environmental landscape. And we need to have a nuanced discussion of how genetic prediction should be and should not be used given that insight.

[Lynne Thoman]

So genetics and the environment, how important are they Both? Is it 60, 40, genetics versus the environment? Is it 90, 10? Where do you come out?

[Dalton Conley]

There was a recent review article that looked at 50 years of twin studies which were the bread and butter of trying to separate out genes in environment, and they came to the conclusion across thousands of outcomes that the average was 49% genetic and 51% environmental. And again, you might just look at that and say it's a tie. But I think that kind of misses the point, actually. That's a false dichotomy. Nature versus nurture, and it's nature plus nurture. That really is how things operate. So Even if that 49%, a lot of that goes through how those genes extract nurture in the world.

[Lynne Thoman]

Dalton, what are the three takeaways?

[Dalton Conley]

Number one, there's a genomic prediction revolution happening as we speak. And we should have a public debate about how we want to use genetic prediction in schools, in insurance companies, in fertility clinics, and so forth is an important debate that's missing. Number two, we shouldn't think of genes as a blueprint. We should think of them as a greedy AI algorithm. They need the environment to come to fruition, and the effect of the genes doesn't stop at our skin. And three, we really can't separate out nature and nurture. We should just retire that 150-year-old debate nature versus nurture. How nurture matters depends on our genes, and how our genes matter depends on our environment.

[Lynne Thoman]

So interesting. Thank you, Dalton.

[Dalton Conley]

Thanks, Lloyd.

[Lynne Thoman]

If you're enjoying the podcast, and I really hope you are, please review us on Apple Podcasts or Spotify or wherever you get your podcasts. It really helps get the word out. If you're interested, you can also sign up for the Three Takeaways newsletter at 3takeaways.com, where you can also listen to previous episodes. You can also follow us on LinkedIn, X Instagram, and Facebook. I'm Lynne Thoman and this is three Takeaways. Thanks for listening.