Ancient DNA reveals family of Neanderthals living in Siberian cave

Host: Benjamin Thompson

Welcome back to the Nature Podcast. This week: ancient DNA reveals evidence of the first known Neanderthal family group.

Host: Shamini Bundell

And the latest from the Nature Briefing. I’m Shamini Bundell.

Host: Benjamin Thompson

And I’m Benjamin Thompson.

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Host: Benjamin Thompson

First up on the show, reporter Ali Jennings is heading back in time to find out what family life might have looked like for the Neanderthals.

Interviewer: Ali Jennings

Let me take you on a journey. Let's imagine it's 55,000 years ago, give or take a few thousand years. Homo sapiens shares this planet with another kind of intelligent ape – one that walks upright, makes tools and might have looked not so very different from ourselves – Homo neanderthalensis or Neanderthals. In a cave in a cliffside in the Altai Mountains in what is now southern Siberia, two Neanderthals sit together – a father and his daughter looking out at the river below. But to bring this back to reality a second, is that the way it happened? Did Neanderthal families like this live together like humans? How many others would have made up their group? Where is the girl's mother? And how did her father meet her? Well, now, we may be able to get clarity on some of these questions, and in a slightly unusual way. We may be able to work this out from DNA. DNA from the bones of two Neanderthals, a father and a daughter, as well as 11 others, now forms the basis of a new study in Nature that changes how we understand Neanderthal social behaviour.

Interviewee: Laurits Skov

So, we went to this cave in southern Siberia called Chagyrskaya Cave, and in this cave, there's I think it’s hundreds of thousands of bone tools and animal bones and there’s also 18 Neanderthal bones or teeth from Neanderthals.

Interviewer: Ali Jennings

This is Laurits Skov, a researcher in bioinformatics and ancient genomes from the Max Planck Institute for Evolutionary Anthropology in Leipzig.

Interviewee: Laurits Skov

We've never had that before. We’ve never had like multiple individuals and so there was no telling really what we would find.

Interviewer: Ali Jennings

The Neanderthal remains found in Chagyrskaya Cave and Okladnikov Cave, about 50 kilometres away, gave Laurits and his team a chance to investigate how Neanderthal communities behaved and were made up in unprecedented detail, with DNA from 17 partially preserved bones and teeth. Now, DNA can tell you a lot about a creature but it breaks down easily, so finding enough to properly analyse was very lucky.

Interviewee: Laurits Skov

Just the fact that we can get DNA out of so many individuals living at the same time was very surprising.

Interviewer: Ali Jennings

Part of the reason may have been the climate in the Altai Mountains and the quality of soil in the cave. But we still don't really understand what it was that preserved these remains so well. Even so, only 11 of the remains they studied from Chagyrskaya had enough DNA in them, and even that was broken up into many short strands, which made them much harder to analyse than a contemporary DNA sample. But by examining molecular clues, like the damage done to the ends of DNA strands and by only looking at certain highly variable places in the genome, Laurits and his team managed to analyse the DNA of enough individual Neanderthals to study the relationships between them.

Interviewee: Laurits Skov

I think one of the coolest things is that we found two Neanderthals that were related to each other. So, we found a father and his daughter. Obviously, father-daughter pairs must have existed in Neanderthal history, but just seeing it makes them come much more alive, which I think is really, really cool.

Interviewer: Ali Jennings

Laurits and his team also provide evidence that Neanderthals likely lived in small groups of around 20, which backs up some previous studies. And they also uncovered an unexpected kind of behaviour in Neanderthal migration patterns, and it came from examining the Y chromosome passed down by Neanderthal men and the mitochondrial DNA passed down by Neanderthal women.

Interviewee: Laurits Skov

When we looked at this and we looked at the data for our Neanderthal community, we find that the mitochondrial diversity is much greater, like by a factor of 10, compared to the Y-chromosome diversity, which means that these communities were primarily linked by female migration.

Interviewer: Ali Jennings

Laurits thinks that the women from these Neanderthal communities would, at some point, have travelled to new groups and remained there, whilst the men largely stayed put. This would be a fascinating insight into Neanderthal behaviour. But there are some considerations about the data to bear in mind.

Interviewee: Lara Cassidy

This is one population, one point in time, one place. It's just a snapshot.

Interviewer: Ali Jennings

This is Lara Cassidy from Trinity College Dublin, who has been writing an expert analysis of the new paper. Lara points out that although this may be what was happening in Chagyrskaya 55,000 years ago, it may not have been the case for all Neanderthals.

Interviewee: Lara Cassidy

Neanderthals existed for hundreds of thousands of years, so we're talking a really vast amount of time these groups existed and also in a lot of different environments. So, again, there might have been a lot of variability.

Interviewer: Ali Jennings

Lara also says it's important to bear in mind that we're still not sure if all of the individuals were from the same community, as there's evidence that the cave was repeatedly occupied. But still, she's a fan of the work.

Interviewee: Lara Cassidy

When you're dealing with ancient DNA, especially from very, very old, archaic hominins, like you're lucky to get anything at all, which is why this study is incredible. Like we only had genomic data from 18 individuals, 18 Neanderthals, before this. They've brought that up to about 30.

Interviewer: Ali Jennings

And Lara thinks that these kinds of results are exciting, not only for what they can tell us about Neanderthals, but also for what they can tell us about ourselves.

Interviewee: Lara Cassidy

Finding relatives is really cool, and that's like a big find in this study. But what will be potentially even cooler is finding unrelated individuals that we know were contemporaries because that's an unusual thing about our own species – that our social groups tend to be composed of a lot of unrelated individuals. So, if we could kind of get that information from Neanderthals, that would be really interesting.

Interviewer: Ali Jennings

Knowing whether Neanderthals lived not only in families but also with individuals not related to them could tell us, for example, if they formed relationships with their in-laws, and came to treat them like members of their family, and Laurits has plans of his own.

Interviewee: Laurits Skov

Just this fact that Neanderthals lived in small groups and they're linked by female migration, just to generalise, does this social organisation generalise to other places where Neanderthals live, so studying cases in Europe. And also, this group is around 50,000-60,000 years ago, but what did Neanderthal groups look like 100,000 years ago, 150,000 years ago, 300,000 years ago? We just don't know yet.

Interviewer: Ali Jennings

In fact, this work has already changed how Laurits views our ancient relatives.

Interviewee: Laurits Skov

It is a funny thing, like working with this kind of data. It really changes your perception of Neanderthals. In the back of your head, you know that of course a Neanderthal family must exist. Obviously, they must be able to have children. But there’s something different about when you actually see it.

Interviewer: Ali Jennings

And with this new work, it's not so hard to imagine a girl walking back to camp on a warm summer evening, tens of thousands of years ago in the Siberian mountains, sitting down by her father at the campfire and dreaming about where her future travels might take her.

Host: Benjamin Thompson

That was Ali Jennings speaking to Laurits Skov from the Max Planck Institute for Evolutionary Anthropology in Germany, and Lara Cassidy from Trinity College Dublin in Ireland. For more on this story, check out a link to the paper and a news and views article in the show notes.

Host: Shamini Bundell

Coming up, we'll be hearing about the discovery of a long-lost star map from ancient Greece. Now, though, it's time for the Research Highlights, read by Nick Petrić Howe.

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Nick Petrić Howe

Birds and aeroplanes collide all the time, causing damage that costs the aviation industry more than a billion dollars every year. But now, researchers have come up with a way to dissuade collision-prone birds – the RobotFalcon. Many techniques have been trialled to deter accident-prone avians away from aircraft. But the birds tend to get used to the measures, pushing aviators back to square one. Enter the RobotFalcon. This fibreglass bird-shaped drone is modelled on the peregrine falcon. The real-life falcon is famed for being the fastest member of the animal kingdom, reaching 200 miles per hour when it dives, making it a deadly hunter, and a robot version possibly a good way to deter brazen birds. The team tried out the RobotFalcon in a rural area of the Netherlands, and compared it to a drone and other conventional methods of deterrence. They found that the faux falcon outperformed these other methods are mostly kept the birds away for longer. And the birds also didn't seem to get used to this artificial avian, which remained effective at frightening flocks during the three months of testing. The authors believe the RobotFalcon is an ethical and effective method of deterrence. Swoop on over to the Journal of the Royal Society Interface for the full paper.

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Nick Petrić Howe

Rising electricity bills are probably on many people's minds at the moment, and new research shows how much bills could rise as the climate warms in California. As temperatures across the state continue to rise, many people will adapt to the heat by using things like air conditioning. However, for low-income households, the costs associated with running energy-intensive technologies like these could present a challenge. To better understand the scale of this challenge, researchers looked at data from 300,000 low-income households in California. They found that every day with temperatures above 95° F or 35° C increased bills by 1.6%, and increases the risk of being cut off from electricity due to non-payment by 1.2% in the weeks following. They calculate that by the end of the century, rising temperatures could increase the number of people in the state cut off from electricity by 12%. But that is without accounting for future prices of energy. Given that people may be even more reliant on electricity to shield themselves from higher temperatures, the author suggests this could lead to an increase in people suffering from heat-related diseases unless action is taken. Head on over to Nature Energy for more on that research.

Host: Benjamin Thompson

Finally on the show, it’s time for the Briefing chat, where we discuss a couple of articles that have been featured in the Nature Briefing. Shamini, why don’t you go first this week? What have you got for us this time?

Host: Shamini Bundell

Well, I’ve been reading an article in Science about why women researchers are cited less than men, specifically in this case, in physics.

Host: Benjamin Thompson

Right, and this is an important subject we've covered of course in the past on the Nature Podcast, but what are the new numbers saying then about physics particularly?

Host: Shamini Bundell

So, there's a new paper out in Nature Physics, and the authors specifically wanted to look at physics because physics is behind on a number of sort of measures of gender equity. And of course, there has been loads of research about gender equity and in different sciences and in citation, but they wanted to look at what the issue was in physics and try and dig into a little bit why it might be. So, in this particular paper, they analysed over a million papers published in 35 different physics journals between 1995 and 2020. And they looked at the citations of papers from male and female authors roughly. As is usual with this kind of work, what they've done is they've used a statistical guess based on first names as a sort of proxy for gender, so they don't actually know the gender of the authors and there's almost certainly errors in there. But with a sort of statistical correlation, they've made some sort of broad conclusions, and they looked at who was making these citations as well.

Host: Benjamin Thompson

And so, what do the findings of this work reveal then, Shamini?

Host: Shamini Bundell

Well, as you might expect, they do find, as other research has found, that male-authored papers tend to be overcited and women-authored papers tend to be undercited and have less citations. But the interesting thing is who's doing the citing, and it seems that male teams and male authors are more likely to cite in their papers, papers by other male authors. There's also a slight effect that this paper found with female-led teams and authors being slightly more likely to cite female-written papers. Certainly, in some cases, it's a bit more variable. The other effect they found was that people are more likely to cite male-authored papers when they are writing a paper in a field that they are less familiar with and a topic that's not necessarily their primary area. And there's a really interesting quote in the Science article that suggests sort of why this is, by a researcher who actually wasn't involved in this study, who said, ‘When you're in a place of uncertainty, you want to choose something that has all the status symbols associated with quality, for right or for wrong.’ With the idea being that men are more likely to have certain status symbols due to sort of previous inequity, even when actually the quality of the paper by female researchers might just be the same.

Host: Benjamin Thompson

I mean, I guess the obvious question now is, now what? We have this data, which backs up what I guess everyone thought was the case. What happens?

Host: Shamini Bundell

So, I think these authors were quite keen on not just sort of going, ‘Oh, look, it's terrible. As you might expect, the women are all getting sort of undercited.’ But in looking into why, they are hoping will allow physics to move towards what can we do to kind of balance that. One thing that they suggest that journals could do is publish more women authors. Go out and sort of solicit articles from underrepresented authors, which should help even out that balance a bit. Another interesting factor that seems to be at play is the length of the sort of reference lists, so basically, how many papers you can cite. So, sometimes this is limited. You only have sort of a limited amount of space at a number of citations. And in those cases, the sort of male-authored paper dominance is much stronger. Whereas if you have a longer reference list, and you can kind of include as many papers as you think are relevant, there's much more likely to be a more representative balance between male- and female-authored papers in that list. That might be because when people are squeezed, again, they're perceiving these male-authored papers as higher quality due to other effects, such as sort of status indicators of the authors. So, one thing journals could do is remove the reference list limits.

Host: Benjamin Thompson

Well, if that's something that journals can do to make a step forward in addressing this issue, what about individual researchers when they're working? What can they do maybe?

Host: Shamini Bundell

Yeah, and I think this paper does also say that individual researchers need to be considering this and thinking about this when writing papers, when coming up with your reference lists, and being aware of the problem is actually also quite a big step towards trying to remedy it. There's also one more interesting side note in this article that I wanted to mention, which was actually another paper from last month that was mentioned in this Science article that looked at the average number of citations across a sort of scientist’s lifetime, and found that men had, on average, about 14,000 more citations than women. But they also looked at the citation networks, and they found that this effect I'd mentioned at the beginning, where men are more likely to cite men and women are more likely to cite women, that effect actually meant that they could look at the citation network and sort of hide a particular researcher and basically determine the gender of that researcher just based on who they were citing, which is quite interesting. So, I think for individuals, that citation network and also, to some extent, a sort of social network of the peers that people are aware of and following and interacting with, could be really important to balancing things out in physics and in other sciences. So, that's my story for this week. Ben, what have you got for us today?

Host: Benjamin Thompson

Right, so this is a story that I read in Nature, and it's based on a paper in the Journal for the History of Astronomy, okay? And it's the discovery of what seems to be part of a long-lost star catalogue, right, so coordinates of stars in the sky. And it was made by the ancient Greek astronomer Hipparchus, and it was believed by many to be the earliest known attempt to map the entire sky.

Host: Shamini Bundell

Oh, so is this something that they've kind of been looking for, for a while?

Host: Benjamin Thompson

Yeah, from what I understand, scholars have been searching for this catalogue for centuries, okay. And as I say, part of it may have been found, hidden not quite in plain sight but in sight of different wavelengths of light, and you'll understand what I mean by that in a second or two, okay.

Host: Shamini Bundell

So, where was this discovered?

Host: Benjamin Thompson

Well, Shamini, the story starts with a mediaeval manuscript, which came from the Greek Orthodox Saint Catherine’s Monastery, which is in Egypt, right. But most of the folios, most of the pages of this are now owned by the Museum of the Bible in Washington, DC. And on these pages are Christian texts written in the tenth or eleventh centuries, but a lot of these pages are palimpsests, okay. So, they were written on and then that text was kind of cleaned off and then written on again, like the delete key, I guess, on a modern word processor. But in this case, they've actually scratched off the old text and written over the top. And this is where the discovery was made.

Host: Shamini Bundell

So, some monks have maybe come along and wanted to reuse the paper that this star map was originally on, so it would have been invisible on the page.

Host: Benjamin Thompson

Well, the story continues. You're absolutely right. So, it was assumed then that what was scratched off would be other Christian texts, right, older than that. And so, researchers started examining this, right. It was a summer project for some students to look for this in 2012. But one of them found a passage in Greek attributed to an astronomer called Eratosthenes, okay. Now, this is obviously a bit strange, right? So, in 2017, these pages then were re-analysed using state-of-the-art spectral imaging, right, using computer algorithms and different wavelengths of light to try and see, like, what's going on here. And in the pages was some more Greek writing and some astronomical texts. But when one of the researchers was looking at these re-examined images during lockdown, he found something very unusual – star coordinates.

Host: Shamini Bundell

I can't believe they weren't actually even looking for it and this was sort of like a summer project and they've sort of uncovered it. So, what do these star coordinates and this star map actually show?

Host: Benjamin Thompson

Well, this is only a passage of information of stars in the constellation, Corona Borealis, right. And there's several lines of evidence that suggest that this could have been taken from the catalogue made by this famed astronomer Hipparchus.

Host: Shamini Bundell

So, this was just a sort of tiny fragment of this famous lost star map potentially.

Host: Benjamin Thompson

Yeah, that's right. And the reason they’ve traced it back as Hipparchus potentially being the source of these coordinates is that some of it is written in this rather idiosyncratic manner consistent with the very little of what's left of his other work. And crucially, it's the accuracy of the measurements here that enabled the team to date the observations in the text, and they've gone back in time to work out when these measurements might have been made. And they fit roughly to 129 BC, which was, bingo, when Hipparchus was working. So, obviously circumstantial, to a degree, but it seems to fit, and they might have, say, rediscovered part of this map.

Host: Shamini Bundell

Under all these Christian writings, does that mean they’re going to be going through the rest trying to find the rest of it?

Host: Benjamin Thompson

Well, the researchers hope that as imaging techniques improve, they will be able to find more of these star coordinates. And of course, there's a lot of these pages that haven't been necessarily looked at yet. And broader than that, there are, of course, thousands of palimpsests in libraries and archives around the world that could be hiding these secrets, as I say, just under the text. And I will say to listeners that the article in Nature is fantastic. There's so much more stuff in there, so well worth checking out.

Host: Shamini Bundell

Well, we will make sure that there is a link to that article in the show notes as well as a link to the Science article that I was talking about earlier. But aside from that, I think that is all for this week. Just before we go, I do just want to tell you about a video that we've got up on our YouTube channel. It is about an amphibious robot called ART, which was inspired by turtles and tortoises. It has limbs capable of morphing between flippers and legs. So, look out for a link to that in the show notes as well.

Host: Benjamin Thompson

And of course, don’t forget, you can always keep in touch with us over on Twitter. We’re @NaturePodcast. Or you can send an email to podcast@nature.com. I’m Benjamin Thompson.

Host: Shamini Bundell

And I’m Shamini Bundell. See you next time.