John Hawks

Opening new frontiers in human origins

The talk will look at recent innovations in field and laboratory approaches to human origins, including how researchers are finding new ways to integrate them. John Hawks will take a look at what questions these approaches are likely to answer over the next decade.

FULL TRANSCRIPT 

Lawrence and Fred asked me to come and talk about some things that we could look forward to over the next decade in paleoanthropology, and I'm going to try to give an overview of some areas of our science that I haven't heard very much about this week. Keeping in mind that we've heard a lot about the future of our field this week already, and I'll try to point to people who have shown things that are, I think really, really significant, but understand I'm trying to fill in some gaps and that's really what our field is about, filling in the gaps. So I'm privileged to work in the rising star cave system in South Africa. It's an incredible project and it poses really interesting problems for paleoanthropologists from anatomy to the contextual nature of the discovery to the very physical challenge of working in the cave system. 

I was a little bit surprised last year when to be working underground and it seemed like something subtle had changed. People started talking about me as the designated survivor because Lee had made the decision to go into the Dinaledi chamber and we weren't sure he was going to come back out. So the fact is it's an engaging project and I'm really pleased to be a part of it. It has enabled me to work and collaborate with more than 250 scientists around the world in different kinds of projects and that has given me a perspective on the nature of our collaborations in the field. What's really pushing the field forward is our interdisciplinary nature, our ability to leverage different technologies and different approaches from many fields of science onto the problems that we care about. We've seen a lot of that already this week in the Turkana Basin and it's something that is going on everywhere in the world. 

We really are a rapidly changing science and one of the big focuses of those changes has to do with the nature of collaboration. In Rising Star we're really privileged to have an incredible array of individuals of all ages, from infants to very old adults, and about half of our sample is juvenile and one of the things that I look at as a major shift that's happening in human origins research right now is a shift toward a focus on ontogeny. We have a building amount of evidence about hominin ontogeny from many different avenues. We have, first of all larger samples of juveniles from many sites. I'll point to a couple of those later, traditional approaches like looking at dental eruption schedules, something that we are building out in larger and larger samples using technology to do it. Here's a couple of our Rising Star specimens showing different age stages and the eruption sequence. 

We're also as a field beginning to apply technology in new ways. So, this is a slide from Tanya Smith's work from a couple of years ago from Payre in France looking at Neanderthal ontogeny through the incremental addition of enamel and correlating rare element in isotope exposures to those growth increments so that you're looking at a life history. Of course, we heard about Daniel Green's work with Tanya and others this week doing that in the Miocene right on Afropithecus and developing a daily almost record of oxygen isotopes and looking at seasonal patterns of rainfall in the time capsule of an individual's tooth. That kind of evidence is going to be applied quite a lot more widely, right? We're going to have this kind of evidence from more and more hominins and it's going to build up a finer and finer resolution scale knowledge of ontogeny. 

We've transformed in some ways our knowledge of Neanderthals by doing this, right? This is a slide from Patrick Mahoney's work at Krapina looking at deciduous teeth where you're getting incremental enamel growth during the in-utero phase of development. We're looking at growth and development across the entire ontogeny, and as we're doing it, we're building up new samples and new ways of looking at things, right? We saw Jose's work earlier this week. We have wonderful immature material from Drimolen, from Kromdraai, from Rising Star. We've seen some really wonderful material that's going to be coming out from the Turkana Basin. We've got a lot of stuff that's coming that is kids and we're going to understand a lot about growth and development from doing it. I just wanted to highlight this slide from Zeray’s work with the virtual reconstruction methods and our ability to build an understanding of cranial growth from in some cases fragmented specimens is incredibly impressive. 

We saw that with Jose’s work also, but growth and development is not all about the skull and certainly not all about the teeth, and we've had a bias because of the availability of dental evidence and the availability of those sorts of very fine scaled methods that we're applying to teeth. Post cranial development is also beginning to really take off, right? This is an immature, an infant's actually vertebral column from Rising Star that our team is working on now with Zach Cofran and Heather Garvin. There is incredible juvenile immature material that's coming out from many sites and it's enabling us this from Panga ya Saidi in Kenya. It's enabling us to have an avenue of looking at the correlation between post cranial growth and development and cranio-dental growth and development, which is something that we are really sorely lacking in any other hominins besides modern humans and Neanderthals today. 

So the next decade is going to see a lot of new emphasis on this area of research. Of course, Panga ya Saidi, the Rising Star situation. These bring up the need to have high resolution understanding of the context of many of our discoveries, and that's something that's changing field excavation approaches. Of course, we have actualist research that's being done by forensic specialists to try to understand what happens to bodies when they decompose and the way that sites are formed. That's changing the way that we excavate sites and think about the site formation processes as we think about the role of hominin in the formation of the sites and of course of other organisms. The use of the deep cave setting has gotten renewed emphasis lately, and it will continue to do so. Of course, Rising Star is an example of this, but Bruniquel Cave in France and a number of other localities in Europe are increasing our concentration on the way that Hominins are using space. 

We're used to thinking about home range sizes and other kinds of aspects of spatial use on the surface. We are now moving towards thinking about spatial use underground in situations where hominins are becoming familiar with spaces and making them part of their activity patterns. On the forensic front, I wanted to show this slide, which is from Masalani and colleagues who were working at Denisova cave and they wanted to understand why DNA is preserved in sediment and one of the really interesting aspects of sediment DNA is that you're preserving a record of hominins and other animals, and other plant remains potentially in fungal remains that are in cave settings. Today it's efficient to do this with hominin DNA because of our genetic resources and in Denisova cave, this is really, really strongly preserved. You can see the layers of occupations of different populations of Neanderthal's, Denisovans, ultimately modern humans. 

The only modern human evidence in the cave comes from this sediment DNA. Masalani and colleagues looked in fine resolution at resin embedded sort of sections of sediment and discovered that DNA is preserved in tiny bits of bone and tiny bits of coprolites that are composing these sediments. When you start to understand that our sites are built up from the biological remains of humans, hominins other organisms, you start to look at the assemblages in a different way, right? We're used to working with small fragments of bone as paleoanthropologists. The fact is that amid all of our small fragments of bone are the tiny, tiny bits of decomposed bone and those tiny bits actually preserve evidence and we're beginning to recover some of that evidence. Of course, tiny bits of bone bring the situation with Denisova broadly, right? The existence of a population that we hadn't anticipated would exist and the recovery of DNA whole genome from this particular specimen that opened a new window and understanding the origins and evolution of Eurasian Hominins. 

Well, Denisova is a fascinating site in many ways. I've been privileged to visit the site a number of times. It's remarkable to see the work that's happening there and it has opened a number of technological windows that I think we are seeing applied quite broadly throughout the field. I wanted to talk briefly about ZooMS. So archeology by mass spectrometry an approach that is transforming the way that we look at small fragment collections from sites, right? In this case, Katerina Duka and colleagues began to apply ZooMS in large scale to the faunal assemblage. The unidentified faunal fragments from Denisova for the purpose of quantifying which faunal species are actually represented there, right? If you can make use of all these tiny fragments that compose the majority of zooarcheological assemblages and archeological sites, so that's pretty cool, but in the process, they had the promise of identifying unidentifiable hominin remains, and it was through that process that they've found a number of hominin specimens that now produce genomic evidence, including this one Denisova 11 that turned out to be an individual that had a Neanderthal mother and a Denisovan father, a first generation F1 combination of these two populations. 

So we're beginning to see the opening of a window onto our field that has been closed to us before, for field survey for other kinds of approaches that we do for excavation. This begins to change our perspective on what we're looking at. Of course, with Denisovans, there's this question of how widespread is this population? Who are they? How do they connect to the fossil record we know about? Everyone knows in this room that this is one of the big problems today in paleoanthropology, we're developing information about populations through genetic means, and we cannot connect that to the fossil record when the genetic information is coming from unidentifiable fossils, so this is a big problem. With Denisovans, a number of approaches have begun to address it. At Baishiya Karst Cave, we're seeing the recovery of protein evidence from this mandible that places it close to the Denisovan sample from Denisova cave and also from sediments where we have Denisovan DNA. So, you begin to build up a record of who's who, from Tam Ngu Hao 2 cave in Laos, this really cool tooth porcupine collected tooth that you look internally anatomy. It looks really interesting and in fact protein evidence shows from Fabrice Demeter and colleagues shows that it is also connected to this Denisovan population. So the sample's building up in a way. Penghu, Strait of Taiwan, another really interesting specimen dredged from the bottom of the straits. 

People are wondering what's going on with evolution in China and East Asia broadly, and I got to tell you that over the next decade, this is a big, big focus in paleoanthropology. People wonder who are the Denisovans? This one Homo longi from Harbin China. I was talking with Ni a couple of weeks ago who described this cranium and he said, why are people talking about Denisovans? Who are the Denisovans? Why are they not talking about whether Denisova is actually one of these things we already know about? Right? And that's a change in perspective that I think is going to become necessary over the next decade. We have geneticists that are naming ancient populations. We know all the problems with naming populations when we apply to humans today. Of course, we have to have a way of talking about the entities that we're sort of examining, but in reality, we have a fossil record and the major problem of paleoanthropology is making the fossil record the scaffold of our understanding and with genetics, that is exactly what's going to turn out. 

We're going to actually know who the Denisovans are. They're going to be something that we already know about. So in paleoanthropology we have a number of biases and it's important to keep those in mind. Of course, the bias toward cranio-dental evidence is maybe the most significant one that many of us encounter, but that's beginning to be addressed in terms of the discovery of more and more complete skeletal evidence. This skeletal record of hominin skeletons over the first three fourths of our evolution is building a record that just wasn't there 20 years ago, and that's continuing, right? We're continuing to build up broader and broader evidence of the skeleton across fossil hominins. Our family tree we all know is complicated, and I've gotten to where in my public lectures, I'm talking about what, 20 some species. Now it's hard to leave anybody out, and I've left out many here that we've already talked about this week, and as you sort of examine the tree and look at the early stages of the tree, this classic sort of, Australopithecus, Paranthropus, are there other genera that matter? Is Kenyanthropus a thing? Those kinds of questions that we've had now rolling around the field for more than two decades. In the later Hominin record, we have additional new lineages that we didn't know about before that have to be integrated in some way, and this chart doesn't include the Denisovans. 

This is becoming an interesting problem, and we heard earlier this week from Carrie, the ways that phylogenetic approaches are beginning to build up better and better evidence, but that better and better evidence isn't resolving the questions very easily, right? It's giving us better quantification of the problems in a way. One of the big reasons for our challenges is the fact that one of the significant biases in our record is how loaded toward the present it is. We know a lot more about recent time than we know about deep pastime, and the fossil record is biased in that way. We've discovered some of the blind spots in the fossil record, right? We think we know about what's going on in the middle and late Pleistocene and in fact we don't. In fact, there's a lot of stuff we're discovering now. We're filling in gaps in the best represented times and in the earlier less represented times, we've seen this week significant revisions of dates from some sites, significant discoveries of rare but informative fossils from some sites are pushing back the evidence for many of these lineages and are showing that there's a coexistence of hominins or a possible interaction of hominins that we didn't appreciate before. 

Of course, interactions are a big topic for us. We know that our recent tree from the genetic record is showing lots and loss of introgression, hybridization, lots of interaction of different lineages. Humans, hominins are mixing with each other to go to deeper time and try to build up this biochemical evidence of evolution, we today have the access to proteomics. This is Homo antecessor proteomic results from Enrico Cappellini’s lab a couple of years ago, placed this onto a tree in a way that was really interesting and illuminating in terms of the evolution and origin of Neanderthals, Denisovas and other later African ancestors of ours. This evidence is going to grow. We all know that proteomics is coming, that it's being applied to many of our samples, that we have initial results that are now being reported in public talks and in conferences about Paranthropus. This is something that we're going to see a lot of really soon. 

Of course, new fossil discoveries are super important. I wanted to highlight some that we hadn't necessarily heard about this week from Gona. Really wonderful early Homo erectus cranium. From Drimolen, the earliest identified as Homo erectus cranium in the world at the moment. Also, really wonderful cranial material of Paranthropus. It's just beautiful, beautiful material. Of course, other parts of the world raise really interesting problems also, I want to talk briefly about Southeast Asia. Of course, Homo floresiensis, I don't really need to talk about it very much. It changed the dimension of our understanding of the interactions and evolution of populations. We're still working to understand it, and that is a problem that you're going to see more information about during this decade. Homo luzonensis super interesting, right and Homo luzonensis, I wanted to point out to you this recent analysis by Clement Zanolli and colleagues looking at the enamel-dentin junction morphology of this species compared to other hominins. 

The really interesting thing about this is that you start to document with additional kinds of evidence, additional kinds of observations, the distinctiveness of varied populations and luzonensis, for example, doesn't fit very well with known species Homo erectus, modern humans, Neanderthals that could be candidates to be this. It has its own position in many ways, and the different teeth actually give you different kinds of outcomes. But Zanolli’s work points to another aspect of enamel-dentin junction morphology, which is the reevaluation of fossils we think we know about. In Southern Africa we have a lot of fossils from the Plio-Pleistocene that have been identified as early Homo. Many of them are probably early Homo, but when you start looking at these, you see that many of them are identified on the basis of their teeth being relatively small compared to Paranthropus. What Zanolli's work suggests is that some of these teeth actually fit into Paranthropus and their shape and their morphology, right? 

The enamel-dentin morphology is showing that specimens like SK 15, which shows up down here on the lower right graph, which none of us had any question with some form of early Homo, actually don't map with early Homo when you look at the EDJ. So we have a complexity of evolution that we have to work out, right? It's something where contradictory evidence is arising from things that we thought were kind of simple, and that's a theme, and it's one that's going to continue to work out as we build more evidence. Somebody said to me this morning, more evidence always makes things more complicated, and I think that's absolutely correct. Coming back to the subject of hybridization, Denisova cave, super central and important in this topic. But one thing I wanted to point out, the human tree, which is becoming increasingly complicated, and we heard the other day from Krishna, the way that this tree is being reevaluated in different approaches, that kind of work is really essential, but I think that people should know that this isn't unique to humans. 

The fact is that every other species that we look at seems to have some complexity of this nature. This is work that's come out in the last few weeks on baboon phylogeography, and here's mitochondrial DNA distributions of the six identified baboon species. But I wanted to point to sort of we understand that baboons have origins that are Pleistocene, that they've dispersed from a relatively southern African source and that they've come to inhabit varied ecologies across the continent with varied sort of appearance, varied body size, and they interact with each other quite widely, right? Where the species come into contact is mixing where some of the species today, the Kinda baboon for example, is thought to be a significant product of past mixture of different lineages. So you have this sort of complexity that's built in. You may wonder why haven't we heard a lot more about this? 

And the answer is because we've developed a lot of genetic methods for the human genome, we have a scaffold and a lot of technology is built on having that scaffold. As we develop genomic resources for other animals, we begin to be able to place them in this sort of context. So other primates are a priority. Major, major papers in science just last week about primate genetics and the effects that it has on our understandings of their evolution. This is going to come for other animals that are of great importance biogeographically in Africa. So I'd like to show this slide of various ungulates and their distributions and the way that those distributions all point to the importance of Eastern Africa as a suture zone, joining different subspecies, different species, the ranges of things, and that's where a lot of the sort of interactions and flexibility of species are. 

This is so important to understanding the role of the Turkana basin and the East African Rift more broadly in human origins because humans are not alone in their interactions in this space. As genomics develops, we're going to understand a lot more about the interactions of other species in these spaces, and we're going to be able to compare the phylogeography and understand something about the evolutionary dynamics of those situations. Of course, brain size is super important to us and brain morphology. I just wanted to point that a lot of us are doing work on this with the Rising Star collection. I'm doing reconstruction work to look at endocasts. We have really wonderful work on the Naledi endocasts, we have work that's reevaluating the role of brain size in our evolution, and the fact is that the pattern right now is a more complicated pattern than we appreciated. 

When you piece apart the record evolutionarily of brain size, you see that brain size has diversified in our evolutionary history. It hasn't been a linear sort of progression. It's been something where we have different lineages that are adapting in different ways in terms of brain size. Over the next decade, we will surely see because it's already happening work that's being done by Christophe Zollikofer, Marcia Leon, my collaborator in Paris, Antoine Balzeau, really wonderful work on understanding what endocast can tell us and the ways that brain structure may be relevant to the evolution of humans as opposed to just brain size. 

Now, the last couple of things I want to talk about have to do with challenges for our field that we're facing right now and over the next decade, we have to work to resolve. RF Science is a comparative science. We rely on comparative collections that are held by institutions around the world. All of us, in one way or another have worked with these comparative samples. For those of us working on hominin anatomy, on human anatomy, on human relationships, a lot of those essential samples are skeletal collections. Those skeletal collections have been acquired over the course of more than 150 to 200 years of history, and they were acquired in the past for imperial, for colonial, and for purposes and for the purpose of documenting and understanding and reifying the concept of race. As a result, our skeletal collections today contain the remains of people who did not choose to be part of them. 

It's not only archeological remains, it's the remains of people who were impoverished, who sometimes their bodies were taken by the state and also of archeological remains, including the remains of Native American peoples. Here this from ProPublica shows us a chart of human remains held by institutions across the United States. When we look at collections and their history of acquisition, right, the acquisition of enslaved people into collections, the acquisition of peoples from foreign countries where their remains were taken away. That's something that today's museums and institutions are working to address, and that work is difficult. For us as a field, we have the challenge of assisting with and helping with repatriation. I've worked on repatriation questions, many of you have. We also have the challenge of building resources that our field can use in the future for our comparative work. We have to build new relationships, get people engaged in sharing data about themselves and being willing to be part of anatomy donation problems of contributions of CT scans that were taken for maybe for medical purposes. The kinds of work that we're moving to anyway, we have to broaden this to be truly representative of human diversity.

That is a major challenge for our field and something that we have to tackle very urgently. Of course, a lot of people have talked about the importance of open science and the openness that we have. It is crucial that we do this as a field, that we develop resources that all of us can rely on, and all of us can know their origin, know the communities have been part of it, and know that this is going to be ethical. So it's a challenge for us, and it's a commitment that I have, and I think that probably most of you also share. Of course, I can't end this talk on repatriation without mentioning that we have fossil material that's an urgent need of repatriation. Zambia asked for the return of this specimen for the first time in 1972. 

Richard Leaky and Meave discovered the 1470 skull in 1972. This is a long, long history of refusal, of repatriation, and of course, this is not the only example. There's a lot of examples in the world, and we have to work to make sure that our collections are being equitable to the partners that we have everywhere that our work is being done and build institutions where necessary to enable people to be the guardians and the custodians of their own heritage. Last thing I want to say, a lot of people have talked about Richard's legacy, and I want to say just one word. Nobody's talked about his books. 

I was a kid in a small town in Kansas, and my avenue of understanding our origins when I was a kid was through Richard's books. I have to tell you, it was amazing as a young kid to read and understand that a scientist is a person. Richard's books have such an amazing sense of humor throughout them. They have amazing stories about his collaborations, and as I realized today, looking back at them, such generous stories in many cases, sharing people's work and sharing their names and what they had done and how they were related to the whole project. It's an amazing, amazing legacy, and it's one that reached so much more broadly than within paleoanthropology within universities. It's something that I think is something I certainly aspire to reach when I think about how I'm engaging with the field and the public. I think it's a legacy that deserves recognition, and I thank him for that. I thank Lawrence and I thank Fred for the invitation to be here. I thank all of you for your attention, and thank you.

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