Host: Benjamin Thompson
Welcome back to the Nature Podcast. This week, how to make diamonds not just hard but tough…
Host: Nick Howe
Evidence of incest within the Neolithic Irish elite…
Host: Benjamin Thompson
And a discussion of #ShutDownSTEM and racism in academia. I’m Benjamin Thompson.
Host: Nick Howe
And I’m Nick Howe.
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Host: Benjamin Thompson
First up, reporter Adam Levy has been finding out a new way to toughen up diamonds.
Interviewer: Adam Levy
I have an important characteristic in common with diamonds. No, not my radiant appearance. It’s what we’re like on the inside that counts. You see, neither me nor diamonds are very tough. Now, you might be thinking, ‘Wait, aren’t diamonds famed for their strength?’ And you’d be absolutely right – diamonds are incredibly hard – but hardness and toughness are two different things.
Interviewee: Bo Xu
Hard material is very difficult to deform, so it will keep the shape.
Interviewer: Adam Levy
This is materials scientists Bo Xu. So, squish a hard material, and it will barely deform at all. But toughness describes a different characteristic – how a material responds to being hit.
Interviewee: Bo Xu
Brittle materials will crush into pieces but tough materials can handle this energy.
Interviewer: Adam Levy
And while diamonds are incredibly hard, they are also – like me – not very tough.
Interviewee: Bo Xu
We cannot deform diamond easily, but we can break diamond very easily. You use a hammer to hit a diamond, the diamond will go into pieces.
Interviewer: Adam Levy
But what if you could make a material which is both hard and tough? Normally, the harder you make a material, the less able it is to absorb impact by deforming, and that means it’s less tough. But this week in Nature, Bo Xu and colleagues have made a diamond composite material that is both hard and tough. To do this, the team employed a set of strategies. For example, they use something called nanotwinning. This technique is inspired by the properties of seashells and precisely lines up neighbouring crystals within the diamond. But they also constructed their diamond composite like bricks and mortar.
Interviewee: Bo Xu
You just put brick together and you can push it and this wall will fall, right? But when the mortar and brick structure work together, you can build a very strong wall. You push it and the wall will resist. The mortar, you can say, is a very thin slice different from the ordinary diamond.
Interviewer: Adam Levy
So, while ordinary diamond could collapse like loose bricks, adding thin portions of another material within the diamond composite can help hold things together like mortar. Using not just one but several strategies help make an extra tough material.
Interviewee: Bo Xu
All these toughening mechanics work together to enhance the toughness of our diamond composite.
Interviewer: Adam Levy
Okay, but just how tough was this diamond composite? Well, not only was it as hard as previous materials the team had made, but it was also substantially less brittle.
Interviewee: Bo Xu
The improvement in toughness is amazing, actually. When compared with ordinary diamond, the toughness of our sample is increased to five times.
Interviewer: Adam Levy
In real terms, that means you’ve now got a material that is much more resistant to being shattered, as the group demonstrated with a toughness test.
Interviewee: Bo Xu
So, we drove a small, like a bullet, into the sample. So, basically, our new materials are still in one piece, but for the ordinary diamond, you could clearly see it had broken into pieces.
Interviewer: Adam Levy
The diamond material isn’t the only thing that was tough though. Actually building the material has been a challenging journey.
Interviewee: Bo Xu
We are really excited about this work. But also, we expected this work for a long time, since we are working on this project like for ten years.
Interviewer: Adam Levy
But now the team have the material, they can think of plenty of uses for it. Since it’s more durable, it could provide a longer lasting and, in the long run, perhaps cheaper alternative to standard diamonds for certain applications. It could also open up new avenues of exploration, like drilling deep into the Earth’s surface.
Interviewee: Bo Xu
Currently, we can drill 10,000 metres, but with our materials, we can go in the Earth even deeper.
Interviewer: Adam Levy
But one of the tasks that Bo Xu is most excited to use the material for is creating metallic hydrogen. Theory predicts that hydrogen should behave as a metal at extra high pressures, and this hard, tough diamond composite might be just the material for squashing hydrogen into this form.
Interviewee: Bo Xu
It can provide an ideal instrument to test or to confirm the existence of metallic hydrogen. Everyone is racing for this cause, for the holy grail high pressure science, so we will definitely work in this direction.
Host: Benjamin Thompson
That was Bo Xu of Yanshan University in China. We’ll put a link to his paper in the show notes.
Host: Nick Howe
Coming up, we’ll be hearing about what DNA evidence found in a 5,000-year-old tomb has revealed about relationships within the ancient Irish elite. Right now, though, it’s time for the Research Highlights brought to you by Dan Fox.
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Dan Fox
A spacecraft that whizzed past Venus and Mercury more than a decade ago could help to solve one of physics’ most enduring puzzles – the lifetime of the neutron. Neutrons may be long lived when locked away in the nuclei of a stable atom, but on their own, they decay within minutes. Scientists have yet to agree how long it takes, but now a team of researchers think they’ve found the answer in readings taken by NASA’s Messenger spacecraft. By comparing the numbers of neutrons Messenger detected in space as it flew past Venus and Mercury, with the number expected to be produced by cosmic ray collisions, the team calculated that neutrons live around 780 seconds plus or minus 70 seconds. Take the lifetime of a free neutron off to read that research in full at Physical Review Research.
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Dan Fox
An endangered ocean giant has found sanctuary deep under the Arctic ice. The Spitsbergen’s bowhead whale was hunted to near extinction by the 1990s, and while the whales’ songs were still detected in the waters east of Greenland, scientists knew little about the species’ habits. This challenge was taken up by a team of researchers from the Norwegian Polar Institute. Flying in a helicopter launched from an icebreaker, the team were able to shoot transmitter tags into the blubber of 13 whales. The animals’ paths showed that, contrary to other bowheads, the Spitsbergen’s whales journey south in summer and north in winter, spending the colder months in deep, cold seas, almost entirely covered in ice. The authors suggest that whalers eliminated the population of whales that chose warmer winter seas, leaving only the hardy animals that chose to dwell beneath the Arctic ice. Now, as the population of Spitsbergen’s bowheads recovers, they may face a new challenge as climate change threatens the ice sheets. You can read that research in full at Biology Letters.
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Host: Benjamin Thompson
Ireland boasts the highest concentration of megalithic architecture in western Europe. These vast structures or monuments made of stone are some of the oldest buildings in the world. Some of the most impressive structures are called passage tombs, and Newgrange passage tomb in the Boyne Valley, just north of Dublin, is one of the biggest ones out there. It took around 200,000 tonnes of material to build it and some of this material was transported from up to 70 kilometres away. Its sheer scale has begged the question among archaeologists as to what kind of society must have built these things more than 5,000 years ago. Well, in an unexpected twist, a large-scale genomics project, conducted by Lara Cassidy, Daniel Bradley and their colleagues, might hold the answer. Reporter Geoff Marsh has the story, which begins with some Irish prehistory context from archaeologist Alison Sheridan, who wasn’t part of the research team but has written a News and Views article on the new findings.
Interviewee: Alison Sheridan
It looks as though there have been people in Ireland since about 8,000 BC, and they must have sailed over, and these people are relatable to the kind of hunter-gatherer community that you get in the west of Europe, but they are separated from their contemporaries within Britain. Then the first farmers clearly came in – they were immigrants – and we’re able to suggest that the ultimate origin of these farmers was two parts of northern France. If you imagine about 4,000 BC, people were coming in from Brittany and building very tiny, very simple, megalithic tombs, and over the course of the fourth millennium, these particular tombs, these passage tombs, got bigger and more elaborate, and so what we see in the Boyne Valley is really the end result of this process of aggrandisement.
Interviewer: Geoff Marsh
Are we saying that the knowledge of the traditions behind these big stone structures was imported with the farmers?
Interviewee: Alison Sheridan
Yes, that’s right, at the very, very beginning. So, the whole idea of building megalithic monuments at all to honour the dead is something which was characteristic of the continent of the time, but it was totally alien to the indigenous hunter-gatherer-fisher communities within Ireland and, indeed, within the whole of Britain.
Interviewer: Geoff Marsh
And as an archaeologist, when you come across some of these massive tombs, what hypotheses do they throw up about what sort of society was behind them?
Interviewee: Alison Sheridan
They required so much effort and time and labour to construct them. They suggest a very high degree of organisation. They must have persuaded many, many people to get together and build these things. The obvious hypothesis is that we are dealing with a society that was ranked at the time, and that it was actually an elite that was responsible for the building of these fantastic, magnificent monuments. They designed Newgrange so that the Sun, on midwinter solstice, the rising Sun would shine along the passage and into the chamber, and this was a way that they could say they were controlling the movement of the Sun. The importance of this was that on the shortest day of the year, a farming community would need to know the days were going to get longer and they would be able to plant their seeds and the crops would grow again and therefore having a ceremony that marked the shortest day of the year was a great day of achieving this.
Interviewee: Lara Cassidy
What I think is really great about Ireland is that it’s an island and it’s sort of a terminal point on the continent, so it’s quite a little contained system in itself. To understand prehistoric societies, it’s a nice microcosm to do it in. My name’s Lara Cassidy. I’m a geneticist or I suppose ancient geneticist working at Trinity College Dublin. Ancient genomes have been used a lot to talk about population migration and movement. It’s cool that we’re now starting to see a lot of papers coming out that are trying to move beyond this and talk about political systems. One of the most incredible prehistoric landscapes in the world would have to be Brú na Bóinne in County Meath on the east coast of Ireland. So, this is when megalithic culture really went on steroids. You get these massive, massive monuments, incredible architectural sophistication. I think one of the other great things about megalithic tombs, for ancient DNA purposes, is they almost act like fridges. We’ve managed to get a really good survival of ancient DNA from these tombs, and they’ve allowed us to understand a bit more about the people who were buried in them.
Interviewer: Geoff Marsh
You sequenced 44 whole genomes from Neolithic Ireland, one of which was at this particular heritage site, this Newgrange tomb, and it led to some pretty stark conclusions about the parents of the chap that you found there, right?
Interviewee: Lara Cassidy
Yes, so, as clear as daylight, his parents were first-degree relatives, so either full siblings or parent and child.
Interviewer: Geoff Marsh
Wow.
Interviewee: Lara Cassidy
Yes, and as unusual as that is to find, his burial place is also extremely unique. He is within one of the most grand megalithic structures we have from across Neolithic Europe and not only that, he’s in the most beautifully decorated recess, the biggest recess at the end of the passage. So, yeah, it’s very hard to imagine that his parentage was not socially sanctioned given where he was buried. Most of the time, if you do find sibling matings that are accepted, they’re half siblings. Full siblings are very rare. And these societies all have a lot of things in common. The first-degree incest is restricted to an elite – typically, only a royal couple or royal clan. They’re highly stratified societies. They take multiple wives. The throne has patrilineal descent. So, there are a lot of markers that appear again and again and again that seem to accompany the exceptions to this universal taboo.
Interviewer: Geoff Marsh
You’ve been thinking about this find at Newgrange presumably for quite a long time now. Do you have an image of your head of who he was and what he looked like, and is there any genetic evidence for what he looked like?
Interviewee: Lara Cassidy
Yeah, so we did pigmentation prediction. So, he would have been on the darker end of skin tones that we see in the Irish Neolithic – black hair, dark eyes and very dark skin. It’s hard because we didn’t get a complete skeleton so we can’t do a height profile or anything like that. We don’t have the remains for it.
Interviewer: Geoff Marsh
As if this lucky find linking the archaeological theories with genetic evidence wasn’t strange enough, here’s Lara’s colleague Daniel Bradley with another bewildering piece to add to the puzzle.
Interviewee: Daniel Bradley
There’s one other sort of crazy coincidence, and that is that in the region of Newgrange, there’s other passage tombs and actually a neighbouring one has a medieval myth around it. And the medieval myth is that whenever it was built, it was built by a builder king and in order to build it he got his sister to cast a spell to stop the Sun in the middle of the sky while the men of Ireland built it, and they were to work for him for one day but the day lasted long because the Sun was stopped. And then he slept with his sister and that broke the spell and the Tara never got completed. Now, this is mythology. The interesting thing about it is that before our results, there was some discussion about whether it implied that there was an oral memory that stretched all the way back to the Neolithic period 4,000 years earlier because it had a solar phenomenon in it and Newgrange and other passage tombs have these solar phenomena built into their fabric. What we’re finding now is this crazy story actually chimes with the parentage of the individual that we find in the centre of Newgrange. I’m not qualified to try and argue that oral history can last for 4,000 years, but it’s an interesting, at least, coincidence that we find with our data. The other wing of our data was two Mesolithic individuals. Now, these are hunter-gatherers. They’re the original inhabitants of Ireland. We were hunter-gatherers, of course, before farmers, and we have two of those. They’re separated by about 500 years. And those genomes are interesting because they’re like other northwestern European hunter-gatherers but they’re also sort of different. So, if I was to summarise it, whereas we can tell that the Irish hunter-gatherers share a strong affinity with each other that makes them more closely related to each other than either are to Cheddar Man or hunter-gatherers from the continent, the same is not true for the British hunter-gatherers. There’s some sort of distinction with the Irish hunter-gatherers. They also carry within their genome a signature from lack of diversity which is indicative of them having come from a small population.
Interviewer: Geoff Marsh
Does that suggest then that those early Irish hunter-gatherers will have had to have arrived there by boat, but that there was then very little kind of continued boat movement and mixing between Ireland and Britain?
Interviewee: Daniel Bradley
I think it does imply some level of restriction in that. I mean we’re not going to argue there’s no movement or communication, but there’s a restriction that we don’t see written in the genomes between Britain and the continent. The other aspect of our data that comes from the hunter-gatherers is that it’s now well established from many studies that the first farmers, when they arrive in these islands, are ultimately descendants of Anatolians. So, whenever farming arrives, it’s not a transfer of culture but it’s also a transfer of people. Now, the question is, what happens to the original hunter-gatherers? Do they simply disappear or is there some ancestry in the Neolithic people that stretches back to the hunter-gatherers? Now, we’ve found one individual, just one, from the west of Ireland who was an early farmer but we can tell that his great grandparent was an Irish hunter-gatherer, and what that tells us is that whereas our local hunter-gatherers absolutely were swamped and replaced, there was some legacy, some genetic heritage that filtered through that persisted from them.
Interviewer: Geoff Marsh
Gone but not forgotten. Before I wrapped up, I wanted a final word from Alison Sheridan again.
Interviewee: Alison Sheridan
I think this is one of the most significant bits of research ever to have been done on Newgrange, and it really is a game-changer insofar as the evidence for incest is unique within British and Irish prehistory. The people responsible for the DNA study have suggested maybe it was a way of sort of protecting a dynastic bloodline. I like that. I think that’s quite a plausible explanation.
Interviewer: Geoff Marsh
Does that tally with the hypotheses surrounding these tombs within the archaeological field?
Interviewee: Alison Sheridan
It absolutely tallies with the hypothesis that the people responsible for building these mega, mega tombs were an elite, for sure. And it gives us so much depth into the broader narrative that we’re able to say and the fact too that there were genetic links with people who’d built and used and who were buried in passage tombs elsewhere in Ireland is mind-blowing.
Interviewer: Geoff Marsh
It sounds like genomics and archaeology make fairly productive bedfellows.
Interviewee: Alison Sheridan
Absolutely, and I think that genomics is an incredibly powerful tool. It has to be applied through archaeology in the most careful way because otherwise you can start making really wacky interoperations and that’s a great danger of it. I think the most important thing is that there is a good dialogue between archaeologists and geneticists.
Host: Benjamin Thompson
That was Alison Sheridan of the National Museum Scotland. You also heard from Lara Cassidy and Daniel Bradley. You can find a link to their paper, published this week in Nature, in the show notes.
Interviewer: Nick Howe
Last week, as part of the #ShutDownSTEM movement, we pressed pause on releasing the show for the day to dedicate some time to educating ourselves and defining actions we can take to help eradicate anti-Black racism in academia and STEM. More on the outcomes of that day in the coming weeks and months. Meanwhile, Nature reporter Nidhi Subbaraman has also been reporting on #ShutDownSTEM and racism in academia. I talked to her about this over the phone. Here’s that conversation. So, I think we’ll be amiss to not talk about George Floyd in any of these discussions about racism so, Nidhi, would you be able to just give us a little bit of background.
Interviewee: Nidhi Subbaraman
George Floyd was a Black man who lived in Minneapolis. He died after a police encounter in the city, after he was restrained and knelt on during a visit to a supermarket. He’s one of many Black Americans who have died after encounters with the police, and each time these events occur, there is renewed attention to the fact that Black Americans overwhelmingly encounter violence at the hands of the police compared to white Americans, and this particular loss at the end of May brought out an unusual level of intensity and alarm and grieving and protest to US streets. It was initially in Minneapolis where Floyd lived where people took to the streets to say that police brutality is unacceptable and that Black Lives Matter, and over the next week, it emerged into a national and international conversation about the roots of police violence as well as racial injustice towards Black Americans and Black people globally.
Interviewer: Nick Howe
And in the wake of this, a lot of things have happened, but in your reporting, you’ve been focusing on the response of scientists, especially Black scientists. Can you tell me a little bit about what effect there has been on the community of Black scientists in the wake of this?
Interviewee: Nidhi Subbaraman
So, we’ve seen scientists, Black scientists in particular, be unusually candid about the way they’ve faced racism within their own organisations, within the conferences that they attend, within the lab groups that they have, and spell it out in shocking and alarming detail. Many of them initially were saying how the events of the protests – George Floyd’s death itself – weighed on them unusually and at one level, an invisible, additional burden that they carried that people who weren’t Black within the scientific institution didn’t perhaps recognise. They just had to go on to the next lab meeting. But beyond that, many spoke of ways that they had felt pushed out or left out or faced hostility because of who they were.
Interviewer: Nick Howe
And in that sort of vein, you spoke to a couple of scientists who started #BlackInTheIvory. Can you tell me a little bit about that?
Interviewee: Nidhi Subbaraman
So, #BlackInTheIvory really touched on this vein of honesty and outrage that was taking over Black science Twitter. It was started by two researchers who study communications – a grad student and a professor – and essentially, they just wanted to share their story. They wanted to say how they had encountered hostility in academia, and it really took off at a time when people were ready to share their stories and draw attention to the fact that there was this unequal treatment that they were experiencing in science, in academia at large. So, there was just an outpouring of honest and thinly veiled stories of incidents, encounters, examples of how they had felt like they didn’t belong, how people had felt like their needs weren’t taken seriously, incidents where people felt like they weren’t being supported in the way that they felt that they needed to be within science and within academia at large.
Interviewer: Nick Howe
And one other thing that we’ve seen is recently there has been a strike in academia to shut down STEM. Can you tell me a little bit about this? What was the impetus behind it?
Interviewee: Nidhi Subbaraman
Again, this was rooted in some of the same impulses that drove the open grieving that we saw soon after George Floyd’s death. It was scientists basically saying, ‘Enough. Science needs to stop, take stock of how it is treating the minority groups in it and do justice to the way that they are supported in this space.’ So, two different groups actually had come up with the idea to have a day of striking. Essentially, one of the founders explained it to me, if you had a swarm of protestors who blocked a highway and stopped traffic from moving, could they do that for science so that people would pay attention to the fact that there is unequal treatment and unequal experiences within it. And so, together the two groups, #ShutDownSTEM or #ShutDownAcademia, which was beyond science, and #ParticlesForJustice, which is a group of physicists, including two Black physicists who’ve spoken up on issues of social justice in the past within science, they launched a couple of hashtags - #Strike4BlackLives, #ShutDownSTEM and #ShutDownAcademia – and called on institutions and societies and universities so stop work for a day and think about the ways in which racism persists.
Interviewer: Nick Howe
What was sort of the hope of the organisers? What did they want to see as a result of this action?
Interviewee: Nidhi Subbaraman
I think the immediate ask was to draw attention to the fact that racism in science is a problem, and calling it out is the first step to taking steps to address it. I think their hope is that this puts pressure on powers that be – institutions with money, institutions that make important decisions, universities that make key hires – to look at the way that this imbalance may be influencing the way they decide where money goes, what research gets funded and ultimately, make science a more inclusive and more diverse place, with the hope that the social benefit of science is also similarly wide-reaching.
Interviewer: Nick Howe
And so, I guess the question is for many people who want to show their support with it is what can they do? So, what our Black academics saying is useful for people to support them?
Interviewee: Nidhi Subbaraman
I think I’m seeing many calls for just an acknowledgement that there is this imbalance, that science may not be welcoming to all people, and figuring out how you can help support those groups that say they haven’t felt historically welcome in it. I’m also seeing calls from folks to just understand the issue a little bit, understand what actions or what terms or what comments may add to slights, may add to a sense of, ‘Why do you belong here? Do you really belong here?’ So, sort of educate oneself about how not to cause more hurt. People are also asking for sort of public shows of support that go a long way in the sense that if you observe a case where somebody makes a hurtful or racist comment or a disparaging comment in a public forum, say something in support of the person that it may have hurt. That goes a long way in calling out the issue and it doesn’t sort of burden the person who felt the slight with also speaking up.
Interviewer: Nick Howe
That was Nidhi Subbaraman, one of the reporters here at Nature. You can find links to all the stories we’ve talked about over in the show notes.
Host: Benjamin Thompson
That’s all for this week. Don’t forget, there’ll be another edition of Coronapod on Friday, so keep an eye out on your podcast feed for that. I’m Benjamin Thompson.
Host: Nick Howe
And I’m Nick Howe. Thanks for listening.