← Science In Action
Science In Action
Earthquakes and the first breath of life on Earth
00:31:37
How Myanmar’s tragic earthquake left a 500km scar on earth's surface in just 90 seconds.
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Welcome to Science in Action from the BBC World Service with me Roland Pease. Later in the program, the connection between shingles and dementia gets stronger.
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D
We just keep seeing the strong protective signal for dementia from shingles vaccination in data set after data set and the.
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Pre history of life still written into the genomes of bacteria today.
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For many this is the key turning point in terms of the rise of complex life on Earth.
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Five days after the violent magnitude 7.7 earthquake in central Myanmar, a picture of the true scale of the damage in the closed country is only just beginning to emerge.
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The scale of destruction in Myanmar's second city is massive. In nearly every street in the northern and central parts of the city we saw at least one building that has completely collapsed. The earthquake ravaged hundreds of structures across the city, including a faded brown block half sunk into the ground. It stopped lurching at an angle over the street, looking like it could tip over at any minute. There we met 41 year old Nan Shinhein, her 21 year old son Saihan Pa was a construction worker renovating some offices in the building. I have hope that he's alive, she told me, even if it's a small chance. But rescue efforts had not even begun here and there was no sign that help was arriving. Just one of the many stories in this devastated city.
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The BBC's yoga. To LeMay, who was able to reach Mandalay near the epicenter, the first pictures that circulated the world was of a construction site collapse in Bangkok. In neighbouring Thailand, 1,000km to the south. It gave a good idea of how serious the shaking would be. Closer to the rupture itself. Predictions from the U.S. geological Survey based on measurements further afield were of a 2 in 3 chance of over 10,000 deaths, a 1 in 3 chance of it being beyond even 100,000. Another analysis put the range as 20 to 70,000. The count reported by the authorities to date is well below that. There's another map from the USGS showing a scar of the most intense shaking right down central Myanmar that overlies a well known active fault line, the Sagang Fault, that runs north south, bisecting the country. Seismologist Judith Hubbard says it moves and breaks much like the famous San Andreas in California.
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The Saigang fault is a massive strike slip fault. It slips about 20 millimeters each year. By that I mean on average it slips about 20 millimeters per year. But this slip actually happens very irregularly in earthquakes like the ones that we just saw. So that makes it pretty similar to these large plate boundary strike slip faults like the San Andreas, like the Eastern Anatolian fault which ruptured in 2023, like the North Anatolian fault which goes through Istanbul, like the Sumatran fault which goes down through Sumatra. People are most familiar, of course, with the San Andreas and maybe the Eastern Anatolian fault, but the Sigang fault is just as big.
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And when you say strike slip, so this is, as I understand it, the western side of the country moving north compared to the east side very gradually or in big ruptures like this one.
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That's right. So it is actually moving very gradually, but it doesn't slip along the fault very gradually. So if you look far away from the fault, you'll see one side moving north relative to the other side. And we can track that using GPS measurements. And then the slip at the fault and very close to the fault happens in the irregular jumps.
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And so this was a magnitude 7.7 last Friday, which is a pretty big one. It started near Mandalay, which is one of the major cities, is that right? Now, what does that translate to into the amount of movement?
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So the measurements so far showed that the fault slipped up to about 5 meters. What that means is that if you had a road crossing the fault, like a regular two lane road, after the earthquake, the road would no longer match up. You would not be able to drive from one side to the other because one side would have shifted 5 meters relative to the other side. In other places, the slip was more like 2 to 3 meters. So it depends on where you are along the fault. In this case, a huge length of the fault ruptured. So about 500 km of the fault slipped. So that's a really big deal.
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That's enormous.
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It is enormous. It's huge. And the fault actually runs not just through Mandalay, but through southward to the new capital, Naypyidaw, through many other towns and villages along the way. And so obviously a lot of people were very close to the fault rupture.
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A phrase which I've seen used in some of the commentary is super shear. Explain that.
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C
The word super shear is usually a pretty technical term, but it really just means faster than shear wave speed. So that's super shear. Super shear is a process that people used to think was quite rare, and it's starting to look like maybe it's not so rare. It happens in strike slip earthquakes when the rupture propagates faster than the shear wave speed of seismic waves through the rocks.
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So this is a tear that started up, as it were, near Mandalay and then started ripping down southwards through the centre of the country, is that right?
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But that's exactly right.
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A bit like a supersonic airliner going through the air. This is a rip going through the rocks.
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Yes. So the rupture doesn't happen all at once. It starts in one place where the fault starts to break, and then that triggers continued rupture on other parts of the fault nearby. So in this case, it started near Mandalay. It ruptured a little bit towards the north, but mostly towards the south, and it happened within about 90 seconds. So the, the rate at which the rupture traveled from Mandalay to the south was faster than the rate at which the seismic waves travel through the crust, like the shear waves. And like you say, that creates a sort of sonic boom. I mean, a sonic boom happens when a plane flies faster than the speed of sound. Right. And so you get this pile up of sound waves that hit you all at once. So you can have that also with a super shear rupture. A pile up of shear waves and that hit you all at once, which can lead to a short period of stronger shaking as you experience that boom.
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Does this explain something that puzzled me, which was that we got these pictures out of Thailand from Bangkok, which is a much more open society, so we see things from there, but we saw this astonishing shaking a thousand kilometers away from where it all happened. Would it be this sort of shockwave continuing through the rocks?
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C
So you're right, there's been a lot of interest in the shaking that people felt in Bangkok. And there's a video of this building under construction that collapsed, which was quite staggering. One thing to note is the earthquake started about 1,000 kilometers away from Bangkok, but because it ruptured so far south, the rupture ended up much closer, about 600km away, which is a pretty big difference. People have suggested, like you say, that super shear rupture could be partly responsible for some of that shaking in Bangkok. Other possibilities are that there's amplification of the seismic waves below Bangkok because of the type of sediments that underlie the city. And there's a possibility that there may have been some resonance of some of the shaking in the sedimentary basin underneath Bangkok that might have resonated with the natural frequencies of some of the tall buildings. So we don't really know the answer yet. These are all, all possibilities, because I.
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Suppose what I was doing naively when this happened was to look at what happened 1000km or 500km away in Bangkok and then wonder what the shaking was like in, for example, Mandalay, which is only, I think, a few tens of kilometers from the source of this quake.
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That's really a very important point. And we have measurements of the shaking in Bangkok. We have a lot of measurements from people. They can translate people's experiences into some kind of quantitative measurement of shaking. And of course, there's seismic instruments in Bangkok. What we don't have is good seismic instruments or really any seismic instruments in Mandalay. And so the estimates we have of shaking and Mandalay are based on people's reports and our understanding of how earthquakes behave. The intensity must have been much, much, much greater in Mandalay and all the way along the fault down to towards Naypyidaw and past Naypy Do.
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And that's, for me, the. The worry. This is, as I understand it, in fact, looking at the maps, it looks like this fault, the Saigon fault, has sort of created this valley with the main rivers going through it and everything. The population must be high here. I don't know if the sed, you know, Also going to amplify. We're not seeing a lot of casualty figures yet. How concerned are you?
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I'm extremely concerned. I think that the possibilities range much worse than what's being reported in the news right now. The USGS estimates, based on the shaking that they estimate and the population densities, that 2.8 million people experienced violent shaking, which is really the top number, the top descriptor we ever use for shaking is violent shaking. And another 4.7 million experienced severe shaking. These numbers are really tremendously high. They're some of the worst numbers I've ever seen. And their estimates for potential fatalities are also among the worst I've ever seen.
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Seismologist Judith Hubbard, whose substack Earthquake Insights is one of my go to sources for reliable information when these terrible events happen. Reporting Nature this week lends new evidence to the idea that a common virus is implicated in Alzheimer's dementia, a theory we were talking about only a few months back. The virus is herpes zoster, the cause of chickenpox, and in later life, shingles, resulting the infection re erupts painfully in nerve endings. The new evidence follows the rollout of Zostavax, a vaccine to protect the elderly from shingles, which the researchers say also led to a reduction in dementia cases. Lead author Pascal Geldzetzer says the abrupt way the vaccine was rolled out in Wales gave them a unique natural experiment to reveal the protection.
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What we need in clinical medicine to show that a new vaccine or a new medication works is a randomized clinical trial. And so we may take, for example, a thousand study participants and then throw a coin to assign them to either receive the vaccine or no vaccine. And the power of this is that you have got really good comparison groups because you know that all that's different between the vaccine and the no vaccine group is that the coin landed on heads or tails. And in Wales, we've just got a very similar situation to a randomized clinical trial in the way that the shingles vaccine was rolled out. Specifically, they said on September 1, 2013, the start date of the program, if you had your 80th birthday just prior, you were ineligible and remained ineligible for life, while if you had it just after you were eligible for the vaccine. So we see that just a one week's difference in age across this date of birth cutoff means that your chance of ever getting the shingles vaccine suddenly jumps from 0% to 50%. And so this is really similar to a randomized clinical trial, right? Because we've got again, two really nice Comparison groups, the vaccine eligible and vaccine ineligible group, who only differ in their age by just a few days. So we know they must be similar to each other. And that's really the power of our study and I think why it's so unique.
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And so the point is that the vaccine suppresses it, as it were. The herpes zoster virus is latent within people and as a result it supposed to stop shingles happening. But you were also able to see that it was reducing the amount of Alzheimer's.
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Yes, correct. So we see the strong protective effect for new dementia diagnoses in the future. So specifically, we estimate that roughly one in five new dementia diagnoses are averted through shingles vaccination over a seven year follow up period, which is a large protective effect size, much larger than what we have from currently existing pharmacological tools for dementia.
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How does that correlate with whether they got shingles as well? In other words, is getting shingles part of Alzheimer's or are they both independent consequences of having the virus?
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Well, it really depends what we think the mechanism is that links shingles vaccination to dementia. So I think there are two broad mechanisms that we can think about. One of them is this chickenpox virus specific effect, which is that, as you were saying, the virus remains hibernated in your nervous system for life after you get chickenpox and is in this constant interplay with the immune system as it reactivates and then is beaten back down by the immune system. And this causes some level of inflammation in the nervous system. We know inflammation is a bad thing for chronic diseases, including for dementia. So reducing these through shingles vaccination may well have benefits for dementia development, but it could also be a virus independent mechanism whereby shingles vaccination has a broader immune effect that is beneficial for chronic diseases. And there's more and more evidence showing that vaccines do have these broader effects on the immune system, beyond the specific antibody response that they have been designed to elicit, and that these may be beneficial for chronic diseases like dementia.
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And also with the medical records, we are able to identify individually people who had the vaccine and then weren't going on to have Alzheimer's. In other words, did you get to see individual records or were you just looking at the population level effect? Because presumably not everyone took up the vaccine.
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We have individual level records, but our primary comparison is comparing those who didn't get the vaccine because they were ineligible to those who did get the vaccine because they were eligible. And our comparison groups are People who were just born just around that cutoff, just a few days, a few weeks difference in age. So that is our comparison and how we're able to get at the effect of receiving shingles vaccination on dementia.
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And it's not fully protective, is that right? You're seeing a reduction, so you know that the virus is somehow involved, but it's not the whole story.
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Yes, so we see this protective effect for dementia, but yes, it doesn't protect against all cases of dementia. We also don't know if it prevents dementia forever or if it just delays dementia. These are open research questions because we.
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Were talking just a few weeks ago to someone about the role of brain injury, relating it also to shingles or herpes zoster and the development of Alzheimer's. And so I'm just wondering what the understanding is, you know, with all the research that's coming out along these lines at the moment.
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Well, I think there's an increasing body of evidence showing that viruses that preferentially target your nervous system and that remain hibernated in your nervous system for life may be implicated in the development of dementia. And chickenpox virus, of course, is one such virus. But there's also this growing body of research showing that vaccine vaccines have these broader immune system effects and that these can lead to off target or non specific effects of vaccines. So effects beyond the specific effect that they have been designed to produce.
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A
So which is it you're saying? Is it the suppression of the virus that's happening, or do you think there may be this off target protection?
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It could be a bit of both. It could be one or the other. We don't know is unfortunately the answer. But that's very important, I think, to invest in research to elucidate these mechanisms.
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You've had a very strong effect that you've seen because of the way the vaccine was rolled out in Wales, it's been rolled out in other countries. Are you seeing something similar elsewhere?
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Yes. So this has been really exciting for the last two years where we've just entirely focused on trying to replicate and build on these findings. And we just keep seeing this strong protective signal for dementia from shingles vaccination in data set after data set from different populations and also different countries that have rolled out shingles vaccination in a similar way to the NHS in Wales.
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Pascal Geldzetzer of Stanford University, hoping to take a deeper look at the prospects of protecting us from dementia by vaccination. A reminder, this is Science in Action from the BBC World Service. This is the story of the 1. As a maintenance supervisor at a manufacturing facility, he knows keeping the line up and running is a top priority. That's why he chooses Granger, because when a drive belt gets damaged, Grainger makes it easy to find the exact specs for the replacement product he needs. And next day delivery helps ensure he'll have everything in place and running like clockwork. Call 1-800-GRAINGER Click grainger.com or just stop by Grainger for the ones who get it done. At the BBC, we go further so you see clearer. Through frontline reporting, global stories and local insights, we bring you closer to the world's news as it happens. And it starts with a subscription to BBC.com giving you unlimited articles and videos, ad free podcasts and the BBC News channel streaming live 24. 7. Subscribe to trusted independent journalism from the BBC. Find out more at BBC.com join to finish the first steps of life Long before there were animals, plants, fungi, there were bacteria everywhere. They ruled the earth. They had it all for themselves for maybe two, two and a half billion years or so, evolving and adapting until getting together in more interesting ways. They eventually laid the basis for complex modern life. But given their small size and soft fragility, it's not surprising. The fossil record tells us almost nothing of that early history. Which is why instead, biologists search the genes of modern bacteria to find the imprint of their past evolution. That yields the shape of a family tree, but not the pace of change. For that, you need a big evolutionary hit. You can date to calibrate the evolutionary clock, step forwards. The Great Oxidation Event Prior to the.
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Great Oxidation Event, our Earth environment, our biosphere, was effectively anoxic. There was very little free reactive oxygen around for any organisms that could use that in their metabolism to exploit.
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This is Phil Donahue, an expert at Bristol University. In the prehistory of life, we don't.
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Really know how many organisms could use oxygen prior to that time. Most organisms were probably anaerobic, couldn't use oxygen and were intolerant to it. And so the Great Oxidation Event, where we get a permanent rise in oxygen levels within the atmosphere, a change in redox state from an anoxic world to anoxic world. That would have been a really dramatic evolutionary challenge for bugs that had evolved before that time.
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A
And as much as anything, this change, I think it's sort of written in the rocks more than the fossils of the time.
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E
Yeah, absolutely. Prior to this time, actually, lots of the iron ore deposits that we use to build cars with and everything Else that's when those rocks were deposited, and they were the sink that all available oxygen was drawn into oxidizing free reactive metal within the world's oceans. And they kind of disappear. As we get to the Great Oxidation.
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Event, as I understand it, in terms of trying to understand the deep history of bacteria, the problem has been you have this concept of a genetic clock, of an evolutionary clock, but it's been very hard to work out how fast it ticks. And having this specific event of about 2.3 billion years ago starts to give you a way to calibrate the clock.
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E
Yeah, absolutely. So from living organisms, we can work out the genetic distances between the living lineages. But if we want to work out the timing of divergences, we need to work out the rate at which those changes have accrued within the genome. So it's a kind of a, you know, speed equals distance over time kind of problem. And so we need some sort of temporal information, some geological information, to separate rates and times so that we can calibrate microbial evolution to time. And the way people have traditionally done that is using the fossil record. If you've got a good fossil record of a lineage, we know what age it is. If we know how genetically distant it is from another, we can work out the rate at which those mutations have accrued, and we can extrapolate that across the whole tree to come up with an overall dated tree. But the fossil record of microbes is absolutely appalling. And, and yet we can use this phenomenon. We can infer when anaerobic to aerobic metabolisms have undergone a transformation, it has to be sometime around the Great Oxidation event, not much earlier, but possibly later. And we can use that information to calibrate those branches in which the transition from anaerobic to aerobic metabolism have occurred all the way across the tree, calibrating the entire tree of life.
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Because the Great Oxidation Event, a mass poisoning of sorts, is recorded in rocks which can be dated to 2.3 billion years ago. That gives the timestamp that geneticists need to track the pace of evolution in the distant past. That's what Phil Donoghue has been unraveling with a global team of biologists, including Adrian Davine of the University of Queensland.
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F
So the problem is that if you want to apply this idea of the molecular clocks, you need something called calibration. And a calibration is some piece of information that you can use to connect your phylogeny to some date, some absolute date. For example, it could be a bone that Says that, I don't know, like 7 million years ago, this organism existed on the planet and it can be assigned to this place in the phylogeny. So if we want to obtain a good data bacteria, we need calibrations. So why is it important to use the goe? Because the GOE is something that can be dated in the geological record at 2.43 to 2.33 billion years ago, so it can give even a specific date. And it can also be connected to the phylogeny of bacteria in many different places.
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And it's because it imprints its impact on the kinds of proteins and genes that the bacteria needed to use to live.
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F
That's the idea. So if you really want to connect the phylogeny with the geological record, you have to also say, were those ancient bacteria able to use oxygen or not? So that's one of the challenges of this paper, that we had to recover the phylogeneobacteria first. And second, we had to reconstruct the metabolism of bacteria in those ancient nodes.
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A
That's so interesting. And as you say, the point is, you don't have fossil bacteria, all you have is the living ones. And you have to assume that there's been some kind of gradual evolution over the past 2.3 billion years that you can sort of wind backwards, you can wind the film backwards.
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F
That's the thing. To do that, then we need to use very complex mathematical models that reconstruct how the genomes of bacteria evolve over time. Then what we do is we look at the genomes of present day bacteria, and using these mathematical models, then we're able to infer how those ancient bacterial genomes were.
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A
But as Adrian says, this takes complex mathematical models, otherwise this might have been done long ago. And it also takes a lot of bacterial genomes to be scanned before you can work out how all those past histories fit together. Particularly as bacteria have this neat trick of borrowing genes from neighbours as well as inheriting them from their ancestors. Gerge Seluzzi is the mathematical biologist who brought these challenges together.
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G
There's hundreds of thousands of genomes, but we were forced to take just a thousand because of just a thousand. Just a thousand. Each had about a thousand.
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A
That's quite a lot of DNA, I imagine, as well.
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G
If it were so, each of those would have a couple of thousand genes. So we reconstruct family trees for each gene, and then we also do that for their shared genome tree from essential or special genes which every bacterium needs to have, like proteins in the ribosome and the advantage of that. Instead, the more classic approach of looking at one or two or maybe a dozen genes going back billions of years is very uncertain for any given gene 2 billion years ago in a particular bacterial ancestor. But if we take all the uncertain signal together using this machine learning model, which learns from all the genes, the signal of being able to use oxygen or not being able to use oxygen, then we can make confident predictions. Some genes are actually taken from one organism and put into a distant one, maybe by a virus accidentally. So oxygen use, aerobic metabolism, was spread by horizontal gene transfer after being invented in the ancestor of cyanobacteria.
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A
So this was, in a sense, it was a slow fuse that led to this explosion you mentioned. I want to pick you up on this. You mentioned the horizontal transfer. So it's not just that bacteria inherit their genes from the parent bacteria, but they can borrow them from nearby bacteria in, let's say, in some kind of puddle or something.
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G
Yes. So as far as we could tell, it was invented 900 million years before the GOE. And after oxygen became significant in the atmosphere after the goe, it started to much more rapidly spread. Thereafter, it started jumping all over the diversity of bacteria. And at the same time, these groups which acquired it, you can clearly see in the tree, obtained an advantage which led to them producing a larger set of descendants, a larger family tree.
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A
By capturing those changes 2.3 billion years ago, the team also get a timeline on the patterns of evolution before then, including the establishment of the major lineages of bacteria more than 3.5 billion years ago, and in fact, that they were circulating even earlier, at least 3.8 billion years ago, a date that caught my attention.
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D
Oh, this is it.
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A
Wow. I've always wanted to see this. And when you look at it, we're looking 3.8 billion years back in time, 20 years ago. As producer of a series with reporter Gabriel Walker on the origins of life, I saw what's claimed to be the oldest evidence of life. So here you have the mud flow unit. So that's that kind of pale gray, that pale gray. And it's paler gray here than here. It goes darker and darker. And the dark color in these layers is carbon. All that makes this dark is carbon. So this is carbon that was once living organisms that settled with the clay, you know, raining down very small, slowly through very long time. This, this could represent maybe 10,000 years.
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B
One centimeter would be like 10,000 years.
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A
Easily be, yes.
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B
And where you have the carbon, that's.
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A
The signs of the very first, the very first signs of life, because the carbon has an isotopic composition that is typical of living organisms. If you calculate how much we have together of the black stuff here, we would have millions of years of deposition. And our hope is that by looking at the geochemistry of these rocks, we can learn more about what life was doing to its environment. Now, the new genetic analysis doesn't prove geologist Minnick Rossing's interpretation of those black rocks in his native Greenland, but they're certainly consistent with the idea that bacterial life was around as far back as the geological record goes. What Phil Donahue underlines is the close connection between geology and biology, between rocks and life, that also led to that, that burst of evolution during the Great Oxidation 2.3 billion years ago, that then laid the foundations for the rise of complex eukaryotes like us.
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E
Yeah, I guess the key step is that eukaryotes are all obligate aerobes. They all respire primitively. At least the ancestor of all eukaryotes and its descendants respired with oxygen. And so this metabolism had to evolve before eukaryotes, and it evolved within bacteria, it evolved within the ancestors of the mitochondria that occur in the cells of all eukaryotes.
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A
So, in a sense, we should be grateful for this event that happened so long ago is written in the sort of rocks and so on, but somehow we're living with the consequences of it now.
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E
Yeah, absolutely. Without this environmental change, many people have argued that you couldn't derive sufficient energy, inner metabolism to underpin the kinds of complex metabolisms and body plans that we see within many eukaryotic organisms. And so for many, this is the key turning point in terms of the rise of complex life on Earth. And it's a major threshold in terms of seeking evidence of life elsewhere in the universe. Most people believe it's probably restricted to microbial organisms because such events may be relatively uncommon on other planets.
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A
Quite the thought. I was speaking there to Phil Donahue of Bristol University, as well as Adrian Davin and to Gege Zalosi of the Okinawa Institute of Science and Technology, whose study was just published in Science Moments we should be grateful for. Well, hope you'll be grateful. Science in Action will be back next week here on the BBC. Do join me, Roland Peace and producer Alex Mansfield, for another dose of knowledge.
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B
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At the BBC, we go further so you see clearer. Through frontline reporting, global stories and local insights, we bring you closer to the world's news as it happens. And it starts with a subscription to BBC.com giving you unlimited articles and videos, ad free podcasts and the BBC News channel, streaming live 24. 7. Subscribe to trusted independent journalism from the BBC. Find out more@BBC.com join.