Ancestors & Ancient DNA w/ Prof. Alice Roberts
EPISODE #57
Biological anthropologist Prof. Alice Roberts shares her insights on how sequencing ancient DNA can provide new evidence to help us understand our ancestors, what the latest archaeological discoveries reveal about the origins of homo sapiens, and how an appreciation of deep history can help us navigate the future.
Professor Alice Roberts is a biological anthropologist, author and broadcaster. She’s interested in the evolution, structure and function of humans, and our place in the wider environment. Having originally studied and practiced medicine, she then became a university lecturer, focusing on biological, evolutionary anthropology. She is passionate about public engagement with university research and teaching, and advocates a wider role for universities in society. She has been Professor of Public Engagement in Science at the University of Birmingham since 2012, and has worked extensively with the Wellcome Trust and other institutions in public engagement roles.
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Luke Robert Mason: You're listening to the FUTURES Podcast with me, Luke Robert Mason.
On this episode, I speak to biological anthropologist and broadcaster, Professor Alice Roberts.
"The genetic information is incredibly useful. It adds something to the interpretation, but it doesn’t stand on its own two feet. It has to join in with archaeological analysis to show us the bigger picture." - Alice Roberts, excerpt from the interview.
Alice shared her insights on how sequencing ancient DNA could provide new evidence to help us to understand our ancestors, what the latest archaeological discoveries reveal about the origins of Homo sapiens, and how an appreciation of deep history can help us to navigate the future.
Alice, your work explores how archaeology and genetics can reveal the deep history of Homo sapiens. How has the ability to sequence ancient DNA transformed the field of archaeology?
Alice Roberts: It’s transforming it in ways we couldn’t have anticipated, actually. It’s quite a revolution. I think it’s as big a revolution as the radiocarbon dating revolution in the mid-20th century, where suddenly we had the ability to obtain absolute dates. Previously, dating had really been about relative dates. Something was buried underneath something else and therefore it must be earlier, that kind of thing. Then using styles to try and date across different sites. Of course with radiocarbon dating, you suddenly had that ability to pin a date on something organic.
What we’ve got with genetics is a way of looking at relationships between people, so we can obviously tell if people are related to each other by sequencing their DNA. We can also look at a kind of population level and learn something about population movements and migrations in the past. I think that’s where the really profound contribution to archaeology is coming from. There are questions that archaeologists have thought about and debated for decades if not centuries that actually, they haven’t been able to solve at all until genetics came along. It’s really exciting.
Mason: With some of those big questions and big understandings are what I want to talk about on this episode. It feels like archaeogenomics - as it’s commonly known - is impacting our understanding, not of just familial ties and of history, but of the origins of the human species, more generally. What new depth and complexity does this biological approach to history provide us?
Roberts: It provides us with a completely different way of looking at human history and pre-history, I suppose. Certainly when you talk about the origins of the species, if we look at how we try to understand that before any genetics came along to help, then really you’re looking at fossil evidence and also archaeological evidence, as well as evidence of ancient material culture. Looking at how humans behaved in the past, trying to find signs of advances - I suppose we could call it that - in behaviour which could be linked to the emergence of something like the modern human brain, for instance. Then as far as fossils are concerned, that’s all anatomy. It’s about looking at the differences in the bony structure between humans and our closest living relatives, chimpanzees, as a kind of comparison.
Then we look back at the fossil record and see how we have a group of particular hominids who start to evolve in a direction which includes walking habitually on two legs, for instance, reduced dentition - so teeth getting smaller - and enlarged brain size. We see that in the fossil record.
Then the contribution of genetics is that you can look, for instance, at the split between us and our closest living relatives, chimpanzees. We can look at the genomes of chimpanzees. We can look at the genomes of Homo sapiens - of modern living people. We can look at the differences between those genomes and ask how long those differences have taken to accumulate. That takes us back to the time of the split between us and our closest living relatives. It can be used in that way, as well, in paleoanthropology.
Mason: Have there been any surprising findings from using this method to look at history? Has it actually challenged any of the histories we thought we previously understood?
Roberts: Yeah, and also, as I said, it’s allowed us to answer questions that were unanswerable. There were questions, particularly about ancient migrations that were endlessly debated, but really you couldn’t resolve those until you had genetic evidence to provide the solution.
Because we have periods in the past where we’ve seen new cultures arriving in particular places, and when a culture arrives in a place the question is, how many people are bringing that culture? There have to be some people involved because there is no remote communication. You at least have to have a few people involved in those transmissions of cultural ideas, but you never really knew whether it was just a few people or whether it was a population replacement, for instance.
Taking an example from my book ‘Ancestors’, the Bronze Age has been completely overturned by genetics coming along and saying, actually, the arrival of the Beaker culture in Britain was significant arrival of people into this land. We can see that there was a 90 percent population replacement over a few centuries. That’s really exciting. It then puts the ball back in the archaeologists’ court and now they have to work out how that transition happened over those centuries, just how abrupt and dramatic it was - or perhaps it was more gradual and it was just a case of more and more families pitching up in Britain over those few centuries. Yeah, there are really interesting, big stories coming out now.
Mason: It certainly seems like there are these grand and large narratives that we can ascertain from doing archaeology in this way. Do you find there’s any pushback? We’re the FUTURES Podcast. We look at the future, and when I think of history, I think of stuffy academics doing archaeology and history in a very traditional way of doing things. We’re traditional historians here. Do they find this new approach threatening to the way history has been done traditionally or the way archaeology is being done traditionally? Or is it being welcomed with open arms? Or are you finding there is still competing evidence for how we understand history?
Roberts: A lot of archaeologists are welcoming this new technology with open arms, but there are some people who are kind of concerned about, maybe, reading too much into it or maybe keeping a few hypotheses going rather than plumping for one. I think that particularly the Bronze Age revelation did send the cat among the pigeons. There’s a little bit of tension, but I don’t want to overplay it because I think most archaeologists are really, really excited about archaeogenomics. There will be a few people, of course, who are worried that it’s going to overturn their particular pet theories. But you know, it’s science. You have to be prepared in science for that to happen.
I think in some cases, it’s been a bit of a clash of cultures. What’s interesting, I think, is that the archaeologists and the geneticists are very often using quite different jargon and terminology. There’s a potential there for misunderstanding. I’m working with an archaeologist and a geneticist at the moment, Tom Booth at the Crick Institute in London, and then with a philosopher colleague at the University of Birmingham as well, Henry Taylor. We’re just looking into that. I think there’s a real possibility for just words to be misunderstood, and to create misunderstanding between archaeologists and geneticists. That’s a misunderstanding that just doesn’t need to be there.
That’s quite interesting, those two disciplines because they are two completely different disciplines - or they were two completely different disciplines - that are coming together with their own backgrounds, their own way of looking at the world and their own terminology. I do think they need to get better at understanding each other.
Mason: Do you have any examples of those misunderstandings and how they’re causing conflict in our understanding of history?
Roberts: The word ‘migration’ is a big one. The word ‘migration’, I think, very often is taken to mean a bulk movement of people over a short period of time, in a way that we would use it to describe migrations in the modern world that are political or economic. I think a lot of archaeologists will read that term and that will be their perception of what migration is. Whereas actually, all the geneticists mean is that somebody has moved from where they grew up to another place, where eventually we find their remains and sequence them. If you’ve got enough people doing that, that amounts to a migration.
It’s a nuance, but it’s really important because it doesn’t necessarily mean those kinds of mass migrations that we see in the modern world. It could be something much more subtle that happens over a longer period of time. It is very different.
Mason: It’s more of a growth of a population as opposed to a resettling of an entire population. The idea that we all emerged out of Africa suggests that we left Africa and no one was left when that happened.
Roberts: Yeah, so that’s really difficult as well. We talk about ‘Out of Africa’ which is the name given to the theory that best fits the evidence at the moment - that the human species emerges in Africa some 300,000 years ago and then expands out of Africa. It’s OOA, Out of Africa. You think, actually, a lot of people stayed in Africa.
Mason: Are still there.
Roberts: As you say. Then we use all sorts of language to talk about those ancient migrations which aren’t necessarily helpful either, and quite often borrow biblical language which I often think is quite curious. We’re so far away from using the Bible as a kind of historical text for these ancient migrations but using the word ‘exodus’, for instance, also brings to mind a whole group of people just upping sticks and moving, rather than a population expanding into new territory.
Mason: What are some of the processes behind using genetics to do historical work? Of course, when I think of genetic testing, I think you spit into a tube or someone takes a little bit of your blood, but when it comes to working with burials and the sorts of burials that you cover in your new book, ‘Ancestors’, there’s not usually much saliva or blood left behind, is there?
Roberts: No, there’s not. I should say if you ask me for details about processes, I’m not a geneticist. You should ask Pontus Skoglund or Tom Booth at the Crick. I’ve hung out with them long enough to hopefully give you a bit of an answer here. Also, I can certainly tell you how I would work with them.
They’re first of all sampling bones. Then it’s a question of finding the bit in the skeleton which is the best bit, or which you think is probably the best bit in terms of the preservation of DNA. DNA is a relatively fragile molecule so you want to go for a bit of bone where you think it has the best chance of surviving. One of the bits of bone that has turned out to be very good in that way is the petrous temporal bone. This is the bone on the side of your skull but also it projects underneath into the skull base as well, the temporal bone. The petrous temporal bone is called ‘petrous’ because it’s very, very hard and dense. It’s like a stone. It means it’s the stony bone. Because it’s so hard and dense, that seems to mean that DNA is preserved much better in that bone than elsewhere in the skull or the rest of the skeleton.
What the team at the Crick Institute who are doing this fantastic ‘1000 Ancient Genomes’ project which I’m working with have been finding is that they are also able to get very good DNA from the ossicles inside the ear. The little tiny auditory ossicles, the little chain, the incus, the malleus and the stapes in your ear which connects your eardrum to the cochlear and are a part of the mechanism of hearing. Those three little bones are very often still there inside archaeological skulls, and they’re completely separate from the skull. They’re not attached to the skull so if they’re there, sometimes they’ll just fall out, actually. When you move a skull they’ll just fall out of the earhole, the auditory meatus. Those bones have proven to be really good as well, for preserved DNA.
The first thing to do is to get your sample and then it’s a case of extracting the DNA and kind of combing through it. A lot of it will be the DNA of various bacteria and not humans at all. You’ve got to comb through it and find the human DNA. Although actually, there are people that are looking at the bugs as well. In Pontus Skoglund’s lab, there’s a PhD student, Pooja Swali, who is specifically looking at the bacteria and the viruses that she finds within that DNA sample so that she can track ancient diseases through time, which is another whole area of study that archaeogenomics opens up.
They are in the business, now, of sequencing entire genomes which is exciting. When ancient DNA technology first started providing some information that was useful to archaeologists, it would often be very tiny bits of DNA that the geneticists were focused on looking at. For instance, mitochondrial DNA which is contained in very tiny packages in your cells or sometimes just particular parts of the Y-chromosome, if we were interested in tracing male lineages.
What they are doing now is sequencing entire human genomes. That means that this is then very powerful in terms of spotting these differences and similarities which are really important to look at how related individuals are to each other, just spotting those population movements, and sometimes even reconstructing the appearance of our ancestors, as well.
Mason: I was going to ask, what can this genetic data be used for? Is it still the basis of facial reconstruction, or is that an amalgam of a multitude of things, from the study of the skull and the teeth and radiocarbon dating the bones? What goes into creating something like that? Is it purely genetic information or is there so much more going on when we’re doing those facial reconstructions?
Roberts: Yeah, it’s not purely genetic. Actually, the genetic basis of how you look turns out to be extraordinarily complicated. It’s not like you’ve got one gene for eye colour, another one for nose shape and another one for the mouth. It’s really, really complicated and it is a conversation between lots of different genes, and your environment as well. It’s very difficult. It’s then probabilistic in terms of what we can say about somebody’s appearance.
Still, I would say, in terms of reconstructing somebody’s face, the best starting point is the skull itself. If you’ve got a well-preserved skull, the skull is the scaffolding. It’s the structure of your face and you can then start to build up the face in a traditional way by applying muscles to it, using clay to build up the shape of the face. Or, you can simply use average depths of skin and muscle and tissue thickness at various points all over your face and then reconstruct faces which are thin, or slightly plumper. You’re applying that to the underlying skull. That’s still the major basis of facial reconstruction.
What genetics can then do is give you some probabilistic answers about things like hair colour, skin colour and eye colour. A really good example of that is ‘Cheddar Man’. He’s a 10,000-year-old mesolithic individual whose bones were found in Gough’s Cave in Cheddar Gorge. They were sequenced fairly recently and that led to an estimation of the appearance of that individual. Then my very good friends, the Kennis brothers in the Netherlands, the paleo artists, did this amazing reconstruction of Cheddar Man’s face. It was based on his skull but they then used that information from geneticists who said that “Look, it looks like he had very very dark skin and dark hair, and blue eyes.” It was a really, really unusual combination of features that we don’t really see today, quite striking. That’s amazing to be able to reconstruct somebody with a good idea of their skin colour.
Mason: You’ve mentioned, a couple of times, the ‘1000 Ancient Genomes’ project from Francis Crick. What is their mission here? What is the aim? How will it fundamentally transform our understanding of the ancient world?
Roberts: Their mission is very straightforward: to sequence 1000 ancient genomes in Britain, but to provide a survey which structures across time as well. Going right through from - I think they’ve got some palaeolithic specimens in there - but going right through from the Stone Age all the way through to much more recent eras.
Really, I should say that their other aim is to be led by archaeologists. They’re working very closely with archaeologists and asking the archaeologist what their research questions are, and how genetics might be able to help those research questions. Some of the information they’re hoping to be able to uncover is around wanting to be able to know more about the Bronze Age and this population turnover. We’ve got the 2018 paper which said there was a 90 percent population replacement, but that’s kind of a very broad brushstroke idea of what happened in Britain at the moment, and it’s not going to be the same in all places across Britain. It’s quite a big place. We don’t expect what was going on in the South East to be the same as what was going on in the South West or Wales, or up by the time you get to Shetland and Orkney. We’ll get a much more detailed picture of what we already know about from these broad brush studies with big population changes.
There’s a big focus on what happens in the post-Roman period, in the 5th, 6th and 7th centuries where everything goes a little bit murky as far as the history is concerned. There are some later historians telling us that there were hoards of Anglo-Saxons coming over, and archaeologists have doubted that for quite a long time. We don’t know how profound the arrival of the so-called Anglo-Saxons was. It’s potentially lots of groups from Northern Europe but again, it may be just a few influential people coming over and ideas spreading. We don’t have a good handle on that at the moment and I think we’ll have a much better idea of that by the time the ‘1000 Ancient Genomes’ project is finished.
From individual sites, archaeologists are interested in knowing the proportions of males and females on their sites. That’s something that those genetic studies can show. Relatedness within sites, too. We’re seeing some really interesting findings emerging, looking at things like communal tombs in the Neolithic. One hypothesis was that these communal tombs are almost about anonymising the dead. The people in those tombs are anonymous representatives of their ancestors.
Another idea in stark opposition to that has been that these are family tombs. These are almost like family crypts. We are finding now, from some studies, that there are definite relationships between individuals buried in those tombs. There was a big survey of Irish neolithic tombs, for instance, showing that there was a father and a daughter buried in one tomb at Primrose Grange. I think between Primrose Grange and another tomb that was very close to that, about two miles away, there was a father and a son. We’re seeing this pattern emerging again and again with more tombs as they’re being investigated. Lots of information about how societies were constructed, how they viewed themselves, and how they viewed themselves in life and in death.
Mason: Well it seems like that’s the tricky thing. The science of genetics is more readily available. It seems like it’s getting increasingly easy to do this process of archaeogenetics or archaeogenomics. What is the process of going from biology to biography, as you’ve said there? The process of taking all of the scientific data and then trying to build the story around the reasons why certain cultures may have done certain things within their burial sites or as a community, or as a society.
Roberts: Those are leaps of interpretation. I think the geneticists are not really willing to take those leaps into interpretation and speculation. They will provide their data to the archaeologists and then the archaeologists need to put everything together. Genetics is telling you biological facts about those individuals, and that’s part of their biography, but there’s so much more to being a human than just your biological basis. For most of us, it’s the cultural milieu. It’s the culture that surrounds us, that we’re involved with, that we helped create and that we learn from. That’s what archaeology itself focuses on.
I think genetic information is incredibly useful. It adds something to the interpretation but it doesn’t stand on its own two feet and it has to join with archaeological analysis to show us the bigger picture. It’s not like genetics is replacing archaeology at all. It’s just another tool that archaeologists can use.
Mason: It sometimes feels like some of those details that were revealed are uncomfortable truths. I know you’ve spoken before about the fact we’re finding out that human beings engaged in incest and cannibalism. All of these things that we never assumed before may be parts of certain societies.
Roberts: Yeah, I think that archaeologists have never been particularly worried about uncomfortable truths. Genetics is revealing examples of incest. We know that incest happens and we didn’t ever doubt that it happened in ancient society. It’s interesting to look at that from a different perspective. Cannibalism is something which we knew about already and that’s not really a genetic finding. That’s more about looking at bones and pouring over scratch marks and cut marks on bones. It’s about looking at the way that bones were smashed into and eventually saying, “Yep, okay, this does look like cannibalism.”
Again, there’s another really good example of that from my book which was the remains, also from Gough’s Cave, but a little bit earlier than Cheddar Man, where there’s a whole pile of smashed-up bones and the remains of six individuals that have been analysed, poured over and we seem to have incontrovertible evidence there for cannibalism in Somerset, 12,000 years ago.
It’s a bit odd because not only is there evidence for cannibalism. There seems to be a ritual element to it as well. There’s a zig-zag incision inscribed on one of the bones and then one of the skulls has been turned into what looks very much like a cup. It’s been kind of chipped. The base of it has been chipped off so that you could then turn the top of it upside-down to form a kind of bowl or cup, which seems very macabre to us, today, but it’s fascinating to look at the range of behaviours that human societies engaged in.
Mason: Well the case studies in the book all focus on Britain. The subtitle is ‘The Prehistory of Britain in Seven Burials’. How are we finding that Britain itself is a vastly more fascinating place than we thought it maybe was?
Roberts: Yeah, I think any British archaeologist kind of knows that. The archaeology in Britain is incredibly dense. People have been here for a very long time. We’ve got people here before the peak of the last Ice Age. I talk about the evidence for a burial that goes way back to about 34,000 years ago in the book - the ‘Red Lady of Paviland’. People then cleared out Britain at the peak of the last Ice Age. It was uninhabitable. Ice sheets came down as far as the Severn Estuary and it was tundra to the South of that.
When people started to come back to Britain, we had hunter-gatherers coming back in at the very tail end of the Paleolithic Age. Then Mesolithic hunter-gatherers are the sort of people who may have been eating each other at Cheddar Gorge, and later on, Cheddar Man himself. Then we have farmers arriving about 6000 years ago, bringing their crops and livestock with them. Then you have the Bronze Age and the arrival of metalworking. The Iron Age. The Romans arrive. It goes on and on. It’s layers and layers and layers.
Mason: Yeah, layers and layers.
Roberts: In some sites, you get all those layers in one place. I’ve just been filming the ninth series of ‘Digging for Britain’ this year. I’ve been filming all around the country some very exciting archaeological sites and new discoveries. One discovery, which I can reveal and spill some beans on, is the site of the St Mary’s Old Church in Stoke Mandeville. That was a fantastic example of one of these sites where the depth of archaeology was so much deeper than the archaeologists anticipated when they started digging. They knew they were excavating the remains of a ruined church which they knew went back to the Norman period. Underneath that, they found archaeology dating to the earlier Anglo-Saxon period. That was very exciting to know that there was a pre-cursor to that church and that place, and Anglo-Saxon dated burials as well. Underneath that, they found Roman archaeology.
What’s astonishing about that is that at the very beginning, they had this question about why there was a church isolated in a field. It’s not in the settlement or next to the settlement. It’s sort of off in the fields, all on its own. There was always speculation that that place might have been special or sacred for a long time, but they still didn’t expect to find amazing Roman remains. They found Roman funerary archaeology in the form of cremations in urns and a beautiful glass jar which may have been a cremation urn as well. They found some astonishing Roman sculptures, really beautiful. We don’t know who they are at the moment. They might be people who were cremated in the pots or they might be Gods and Goddesses - we’re not sure - but they’re really beautiful sculptures and a very, very rare find in Britain. It’s lovely to have that depth of archaeology in one place, going back through Norman, Anglo-Saxon and Roman.
I jokingly said there’s probably an Iron Age layer as well. In actual fact, there may have been a Bronze Age burial mound, because certainly the ground has been mounded up. Maybe there was something there even before the Romans, which has been destroyed by later archaeology, so we can’t really see it now.
Mason: It does feel like, especially now post-Brexit, we have this identity crisis about what Britain is. Is there something that British folks could learn from ancient history, about the fact that we are essentially a country full of these wonderful layers?
Roberts: I think history and landscape are really fascinating. I wrote that book thinking about people engaging with their landscapes. Especially over the years of the pandemic and through the lockdowns when I think people discovered a newfound love of the British countryside. For me, walking in the countryside is very much about enjoying being outdoors, enjoying nature, and enjoying wildlife, but also thinking about the heritage that is written into our landscapes and spending quite a lot of time looking for obvious bits of heritage in the landscape.
Oxford University has done a fantastic map of all the Iron Age hill forts. You can look at them all. I’ve got this slight ambition to visit all of them in my life. In the way that people bag Munros, I want to bag all the Iron Age hill forts, which I think are wonderful.
I do think that when you take the long view, you just see that nothing stands still. I think that’s really important. We might want to be socially conservative over a short timeframe - especially politically conservative - but actually, it’s always changed. There have always been new people coming, and new ideas as well. Those ideas have enriched our culture over time. When you look at the arrival of all these different cultures and different ideas in Britain, that’s what makes us today.
Mason: It’s always astonishing to me that it’s quite literally in our backyards in Britain. My personal engagement with history as a young boy was going to our local museum. The local museum didn’t have the same appeal as the Roman villas and the castles that you go to, but it was always astonishing to me that Dartford Borough Museum would have this skeleton of a man who was found in the town of Dartford, of all places. It was astonishing to me. Oh God, there’s history right out there on your front porch. Do you think that’s something that’s very unique about British history compared to other countries, for example?
Roberts: No, I don’t think it’s unique at all, but it is important. It’s important that you can engage with your local area in that way. I’m just the same as you. That’s how I kind of started off with my love of history. It was at the local museum. I grew up in Bristol. It makes it much more relevant, doesn’t it? If you’re looking at archaeology which is local to you. You’re not just thinking of archaeology being somewhere else. You’re not thinking of it just being Stone Henge, for instance, in Britain, or being the pyramids; something far away and not necessarily that relevant to you and your area.
Then learning about the depth of history that’s written into the landscape all around you, as you say. As you step out of the door, think about all of the people who’ve lived in that landscape. That’s why I love it.
Mason: You said something so wonderful which is the idea of attending a museum as a form of ancestor worship. What sort of relationships should we have with our museums here in Britain?
Roberts: Well I think we do love our museums, and we need to remember our love of our museums because they’ve had a tough time over the pandemic. Obviously, being shut for long periods of time, and then having reduced visitor numbers. I really hope that as we start to - well, I hesitate to say ‘emerge out of the pandemic’ because we’re still in it at the moment - but we can return to doing these things and we can be careful. We can wear masks to protect each other still. We do need to remember our museums. They’re wonderful institutions. They’re wonderful to visit. They’re wonderful places that are inspiring to children. Both of us were interested in and inspired by museums when we were younger.
Then, of course, they do so much other work as well. They work with schools. They work with local communities and are constantly working on new ways of engaging more widely and more fully with those communities.
They’re also repositories of amazing stuff. That’s what’s important about museums. I’m really pleased that museums seem to have gone on an interesting journey - we always talk about ‘journeys’, don’t we - during my lifetime, when I think a lot of digital technology started to come in, in the 80s and the 90s. Perhaps some of the objects went away, and we had lots of touchscreens and interactive displays instead. Now, I think there’s probably a return to a good balance between that new tech, and also recognising the power of the object in the museum. It’s fine to be watching a video about something or looking at an interactive display, but you really want to go to The Salisbury Museum and see the ‘Amesbury Archer’ laid out. You want to see the bones of the ‘Amesbury Archer’ and all of the objects that were buried with him in the grave.
The interesting thing about that, I think, is that you might go to a museum and see a human skeleton, and some people might not want to do that. I think that that’s absolutely fine. It’s just individual preference. For me, it feels like a deeply reverential, respectful thing to do. It is like ancestor worship. It’s us paying our respects to those ancestors that went before us; in the case of the ‘Amesbury Archer’, 4,500 years before us.
Mason: Where did your love - not just for museums, Alice - but where did your love for archaeology come from? I was surprised to learn when researching for this podcast that you originally trained as a medical doctor. You went from a nice, clean medical environment to dealing with dirt under your fingernails and dusty museums. How did that transition happen?
Roberts: Yeah, medical environments aren’t always nice and clean. You get other things under your fingernails. Anyway, I should be a surgeon. I trained as a medical doctor, as you say. I did my house jobs over in South Wales and then I was looking around for the next job and spotted this job at Bristol University which was teaching anatomy to medical students. I loved anatomy. I still love anatomy and I still teach anatomy to medical students at the University of Birmingham, now.
Alongside that anatomy job, I knew there was the potential to get involved with a bit of research as well. I knew that there was a forensic anthropologist in the department, and I was quite interested in forensic anthropology and archaeology as well - osteoarchaeology in particular. When I arrived in Bristol, I was lucky enough to meet all these people who are working in that particular area. There was a whole research group working in that area. I started looking at old bones and becoming fascinated with them. On the afternoons that I wasn’t teaching anatomy, I would be in the basement of the old Bristol Royal Infirmary looking at ancient Medieval bones. I was laying out the skeletons, learning how to assess a skeleton and writing a skeleton report for archaeologists.
It’s useful to be a medic, as well. It’s useful to be a medic. It’s useful to be a medic and an anatomist and to have a bit of knowledge of bones. Not only bones but all of the other stuff that goes around bones. When you see a particular prong sticking out of a bit of bone, you can go, “Oh yeah, I know what that is. That’s where a particular ligament attaches, and that’s ossified.” It kind of felt to me like a very natural transition.
Although having said that, I didn’t expect to stay doing that teaching and that research. I then thought I’d be going back into the world of clinical surgery. I then ended up with a series of rolling contracts and I stayed on the job and thought, actually, I’m really enjoying this. Then I started a part-time PhD looking at disease and ancient human remains. By that time, I think once I’d embarked on a part-time PhD, I think I’d decided that I probably had stepped away from surgery and become an academic. I had this brief sojourn outside of university and then went straight back in again.
Mason: Of course, you’re also known for your relationship with ‘Time Team’. You started ‘Time Team’ in 2001. The wonderful thing about ‘Time Team’ - it’s a show I grew up with as a kid and it was always on on Sunday afternoon or Sunday evenings - it always seemed like everything they would get out of the ground would be so incredible. There was nothing ever banal about the stuff they were finding on ‘Time Team’.
You’ve critiqued that in some way. You’ve looked at how some burials get this wonderful ancient, sacred status, simply because they survived and simply because they weren’t washed away or didn’t decay. Is everything that we find, when it comes to archaeology, always so profound? Or, sometimes, are there just basic banalities that we come across in this archaeological process?
Roberts: There’s a whole range, yeah. I would argue with that on ‘Time Team’, actually. I mean, there was one in particular that I remember, that I was on, where we thought we were going to find something to do with a Roman fort, I think. We spent three days digging and found a path - a buried path - at which point lots of people start dressing up. If you’re watching our old re-runs of ‘Time Team’ and there’s lots of dressing up, it’s because there’s not that much archaeology coming out. There was always a backup plan.
Mason: Secrets from the old.
Roberts: Yeah, there was always a backup plan. It was such a lovely series to be involved with. That really did set off my television career. Again, something I wasn’t expecting at all. It very much was that one thing led to another. I started as an expert contributor. Actually, even before I appeared on ‘Time Team’, I was working for them as a specialist. I was getting skeletons that they’d excavated on their site and was writing reports for them. Then I was invited to come along on screen and talk about bones. They obviously decided I probably could talk about bones, so they kept on inviting me back as an expert contributor.
It was just a lovely, lovely series. Lovely people to work with, really fun, and just fed back into my own research as well. The bones that I was helping to dig up whilst we were filming would then be brought back to my lab and I’d run whole research projects with my students on them. Yeah, it was fantastic.
But they didn’t always find profound discoveries. I suppose the thing to say is that when you’re actually digging, all of it’s exciting. Even if you’re finding something very small - a bit of clay pipe, for instance, maybe a bit of Victorian clay pipe - these things are not unusual. People find them all the time. But you’ve found it. You found that one. That’s a connection between you and another person in the past. There’s something profound about that, I think. It’s that kind of intimate connection, at that moment, between you and this other person that’s long gone.
Mason: That’s part of history. I would be remiss to ask, is there a favourite clay pipe that you have, Alice? Is there something you’ve found that has this profound relationship with you and your history of archaeology?
Roberts: Well there is a lovely one on ‘Digging for Britain’ this year, actually. Do watch ‘Digging for Britain’, because there’s a very, very beautiful clay pipe that emerges.
Mason: I do have to ask, and I want to zoom back out to look at this larger picture of the human species, more generally. That’s the wonderful thing that ‘Ancestors’ does. It makes us realise that, as you said previously on this show, science is always evolving. Science is always changing. We’re always updating our views and opinions on what we think human being is and could be. One of those big questions is simply just, how old our species is. Why is that always changing? What does that tell us about how little or, I guess, how much we know about the human story?
Roberts: Yeah it’s interesting isn’t it, because you get these kinds of headlines about new fossils being discovered or new dates coming out. Looking at paleoanthropology now, and looking at the origins of Homo sapiens. Sometimes there are big changes. Sometimes there are changes that are reported as big changes but aren’t actually as big as they might seem.
One of the amendments, I suppose, which has come along in relatively recent years was that, well…going back, I made a series for BBC2 about ancient human migrations, but also looking at the origin of the species in the first programme of that series. It was called ‘The Incredible Human Journey’. That was a while ago. It was back in 2008, and I think it aired in 2009. When we were making that series, the oldest modern human fossils - so, bones which looked as though they were definitely human bones, modern sapiens - came from Ethiopia. We travelled to Ethiopia and I went to the original find spot, which was amazing. Richard Leakey found the bones at Omo Kibish and the fossils are named after the find spot.
They had been recently re-dated. They were originally thought to be around 65,000 years old, when Richard Leakey discovered them, which seems reasonably old and ancient. But they’d been recently re-dated by a team that had gone back to the original find spot and had dated layers of volcanic tuff above and below the fossils. They’d found that the fossils were lying virtually on top of a layer of volcanic tuff which dated to 200,000 years ago. They argued the remains were actually almost 200,000 years old. That was a really interesting finding that we reported on in that series.
A few years later, there were excavations going on in Morocco at Jebel Irhoud, at a site which had yielded previous fossils but then yielded some more. Anthropologists were looking at these fossils and saying, “They have some archaic features - they have a long head, for instance - but the face looks very modern. We do think that these are examples of modern humans, Homo sapiens.” The date of those is around 300,000 years ago.
Suddenly, you have this kind of leap. When you hear about it in the news, it’s like, “Oh my God, humans are 100,000 years older than we thought.” Having said that, we knew that there was a likely split between us and the population that then evolved into Neanderthals, going back even earlier than that. It didn’t make us rip everything up. It just pushed that date for the accumulation of modern features back a bit. It’s just what you kind of expect. It’s not outside of what you expect.
Mason: Interestingly, genetic studies have shown some interesting relationships between Homo sapiens and Neanderthals. It’s fundamentally changing our perception of what a species is. The story isn’t as simple as we thought, is it? In actual fact, the relationship between Homo sapiens, Neanderthals and all of the other different types of hominids is very interrelated, when we look at our history.
Roberts: Yeah it really is. That’s very exciting, actually. Again, it’s something that we didn’t know about when I made ‘The Incredible Human Journey’ series - that’s going back just 13 years ago.
When we were looking at the potential idea of modern humans and Neanderthals having interbred with each other, which was certainly an idea that was hotly debated, I came down tentatively on the side of there being no interbreeding in that series, very much following the opinion of Chris Stringer, the Head of Paleoanthropology, at the time, at the Natural History Museum. Having spoken to Chris about it, I thought his interpretation was quite sensible.
There were a few skeletons that had been purported to be hybrid individuals that had a few Neanderthal features as well as modern humans. The problem is there, of course, that Neanderthals and modern humans have a common ancestor. Are you just looking at somebody that’s got a feature which is just an archaic feature that’s still hanging around, rather than a feature which has been newly introduced by some interbreeding with Neanderthals? I think most paleoanthropologists thought there wasn’t much evidence, just looking at the anatomy. Looking at the shape of bones and skulls, for instance, there wasn’t enough evidence to say that there had been interbreeding between modern humans and Neanderthals.
The archaeology didn’t necessarily suggest that there had been either, although there were some archaeologists, Joao Zilhau, who is a Spanish archaeologist, had been arguing for a long time that there are transitional cultures that we see in the archaeological record that do look like the kind of thing that you would expect if modern humans with their culture and Neanderthals with their culture had actually met and shared ideas. That’s really interesting.
Anyway, then genetics comes along and just goes, “There you go. We’ve just found evidence of Neanderthal in DNA in modern human genomes.” Not just archaic DNA that’s somehow been inherited from that common ancestor, but clear signs of introgression and of DNA arriving in the modern human genome. The only way that DNA can arrive in a genome is by interbreeding.
Then you go, well hang on a minute. If there’s Neanderthal DNA in modern human genomes - I’m 2.7% Neanderthal - that means that those interbreeding events, if we can cautiously call them that, mean that those children were fertile. If they’d been infertile, I wouldn’t end up with any Neanderthal DNA. You’ll have Neanderthal DNA in you as well, Luke.
Mason: Oh right.
Roberts: So we wouldn’t have it if they’d been infertile. What we’re saying is there has been interbreeding between two different species, and the hybrid offspring are still able to reproduce. Of course, there’s a very basic definition of species. There are lots of definitions of what a species is - it’s something that biologists argue about a lot - but there’s a very basic definition of a species which is essentially that two species can’t interbreed with each other and have fertile offspring. Genetics has just blown that out of the water. We can see that very clearly.
It does make us scratch our heads and make us ask whether we’re sure that Neanderthals are a separate species. Are they just sub-species, and we’ve got two separate subspecies that are able to reproduce? Some geneticists would say that. Some geneticists would say that, yep, we’re looking at two subspecies and not two completely separate species. But I think most people working in the field agree that they are two separate species and morphologically they are quite distinct. You won’t mistake a Neanderthal skeleton for a human skeleton. They’re very, very different looking.
We are at that point now where we’re saying that closely related species clearly can interbreed and have fertile offspring. There might be some issues with fertility, but not enough to stop children from being born, and not enough to stop that DNA from being transmitted all the way down generations to us in the modern day.
Mason: It certainly feels like this sort of work forces us to question the grand narratives that we have for history. We make so many assumptions about where human beings come from or where the human species comes from. That’s largely due to how science and the history of humanity are taught to children in schools. There is a very clear-cut narrative there. One of those narratives that it feels like a lot of your work is beginning to question is this idea of the common ancestor. Did we all originate from the same couple, at some point? Or is that just purely a misunderstanding of the science and maybe a little bit of Judeo-Christian religion story has been attached to that, there?
Roberts: Yeah, it’s interesting. Because we’ve got this ability to decode DNA and then trace back lineages through time, you can look at, for instance, mitochondrial DNA which you inherit from your mother and you can trace it back, and back, and back, and back, and back. You would get to a point in time where everybody’s mitochondrial DNA comes from one woman. She’s sometimes called ‘Mitochondrial Eve’ in the literature, as well, which again is another biblical reference that I think is actually unhelpful. It gives you the idea that there was just one woman around 200,000 years ago when we think ‘Mitochondrial Eve’ existed. There weren’t. There were many, many women. She was just one among thousands of women, but it happens to be her DNA that everybody has inherited. It’s just a statistical quirk that it’s her. Also, the point in time isn’t that important either. It’s only important for that strand of mitochondrial DNA. It doesn’t have any meaning beyond that.
You can do the same thing with the Y-chromosome until you get back to ‘Y-chromosome Adam’, who definitely was not in a couple with ‘Mitochondrial Eve’. He lived at a completely different time and a completely different place, which shows you how nonsensical it is. The human population has gone through some bottlenecks. It’s gone down to quite low numbers, sometimes just a few thousand people, but it’s a few thousand people rather than a couple. That’s not how evolution works, is it? You don’t get whole species from just a male and a female starting a species.
Mason: The issue becomes that those stories become memetic and they’re the things that people think and remember when it comes to engaging with the history of our ancestors. We all have this common ancestor - that’s the assumption that many folks make. How do we help people become more scientifically engaged in their ancestry and in archaeology and genetics, more generally?
Roberts: I think with ancestry it’s quite tricky, and the mathematics of it is really interesting. The book to read there is Adam Rutherford’s book, ‘A Brief History of Everyone Who Ever Lived’. He picks that apart so brilliantly and shows that if you have a common ancestor with somebody else, that’s great, but then you have thousands of other ancestors at the same time. You’re just looking at one lineage back through time to find that common ancestor. We’re very fond of picking out the ancestors that have done fantastic things and then forgetting all of the others who are quite ordinary, or did bad things.
You don’t have to go back very far until your ancestors are in the thousands. If you consider that they double up at each generation, you’ve only got to go back 10 generations until you’ve got over 1000 ancestors. You’ve got two parents, four grandparents, eight great-grandparents, and 16 great-great-grandparents. It’s exponential, so very quickly those numbers expand. When you’re just tracing one line back, you’ve got to remember that there are lots and lots and lots of other lines within your family tree.
Mason: So Alice, why do you believe that it’s important that we learn from our ancestors? How do we apply that knowledge to the way in which we live today?
Roberts: I think there are a number of things. I think that it’s a little bit like that idea that travel broadens your mind and that exposing yourself to other societies, cultures and ways of being human is a good thing. I think it makes you into a better, more tolerant person. It makes you look at yourself in a different way. You can do that by travelling through time in the same way that we can do it geographically today. I think that idea of time travel is really fascinating. It does bring us then back to look at our own culture, and perhaps look at it and think, what are the things which are good about this culture and what are the things that are perhaps not so good about this culture, having had this comparison with the past? Then start to think about the future and think, what do we want our future societies to look like? There is always this two-way mirror, isn’t there? Looking back into the past but also thinking about the present, and also projecting that into the future as well.
I think it just frees us up from thinking that the way we do things now is not the right way of doing things. It’s just a way of doing things. Could we be doing things better? There are some lessons to be learned from the past. There are some things that happened in the past that we definitely don’t want to do again.
Then there are just brilliant stories. I love this intersection between archaeology and genetics. When I was writing ‘Ancestors’ it felt very archaeological to me. It felt like I was digging up amazing stories to put in that book. It’s not a novel. It’s not coming out of my head. These are stories that exist out there, and my job is to go and dig them up and then present them to you.
Mason: This is the FUTURES Podcast. You mention there how this can help us imagine and think about the future. I guess my question then is, how far do you think ancient genetics can actually go? What else might we be able to find out as biological science progresses into the future?
Roberts: I think we’re finding that we can extract and sequence DNA from really, really old remains and remains that we hadn’t anticipated that we might be able to get DNA out of. Even remains that are hundreds of thousands of years old. It was phenomenal when ancient Neanderthal DNA was sequenced, and that was 16,000 years old. We’ve got other DNA from fossil horses, for instance, which is hundreds and hundreds of thousands of years old. That will push back but I do think it will get to a point where that will be finite. We won’t be pushing it back millions and millions of years.
Unfortunately, I don’t think we’re ever going to get dinosaur DNA. That’s a real shame, isn’t it? I would love there to be the possibility of actually getting dinosaur DNA, but no. We’ve got lots of DNA from various Pleistocene mammals, especially ones that get frozen into the permafrost. Mammoth DNA, for instance, we’ve got a good idea about now. Unless we find a dinosaur that has been frozen for 66 million years, then I think dinosaurs are out as far as genetics is concerned. We will get to a point where you literally just come up against a brick wall because there is no DNA there, and therefore you can’t tell any more about it.
In terms of what else we might be able to tell, I think we’ll get better at linking up between genotype and phenotype. In other words, the code and the anatomy and physiology of an individual. The things that we can tentatively say about appearance at the moment, we might get a bit better at doing that, although it will always be probabilistic because it’s a conversation between all the genes and environmental factors as well. I think we can expect more of that. As we learn more about our own genetics and what DNA is doing in living bodies, that will help us to interpret ancient DNA as well.
Mason: Well on those exciting notes, Alice Roberts, I want to thank you for being a guest on the FUTURES Podcast.
Roberts: Thank you very much for having me. I’ve enjoyed looking into the past and thinking about the future.
Mason: Thank you to Alice for showing us how archaeogenomics is helping us to uncover new knowledge about our ancient ancestors. You can find out more by purchasing her new book, ‘Ancestors: A Prehistory of Britain in Seven Burials’, available now.
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Recorded, Mixed & Edited by Luke Robert Mason
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