At first, they thought it must be a mistake. Gene sequencing reveals a surprise in the early modern human family tree

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At first, they thought it must be a mistake. Gene sequencing reveals a surprise in the early modern human family tree

National Science Foundation

Transcript

At first, they thought it must be a mistake. Gene sequencing reveals a surprise in the early modern human family tree.

Interviewer: Jordan D’Eri

Interviewee: Melissa Hubisz

JORDAN: Hello and welcome to Dig This! The National Science Foundation’s anthropology and paleontology themed podcast… hosted by me… Jordan D’Eri… multimedia editor for the National Science Foundation’s Science360 News service… and writer… editor… producer… and co-host for the NSF Science360 Super Science Show. On today’s episode… we’re keeping it all in the family. The human family tree. Specifically, we’re talking about some pretty cool research involving the gene flow from early modern humans into Eastern Neanderthals happening much sooner than researchers originally thought.

JORDAN: first… let’s specify what we mean by “family tree.”

MELISSA: …it’s like a graph that connects all of the genetic samples back in time until they all find a common ancestor.”

JORDAN: That is geneticist Melissa Hubisz… a graduate student at Cornell University and an author of the paper… “Ancient gene flow from early modern humans into Eastern Neanderthals…” which came out in the Spring of 2016 in the journal Nature. So the lead authors of this paper were sequencing genes of western Neanderthals and wanted to see how closely related they were to the Siberian Neanderthal specimen they found. What they noticed was that there was some sharing of African DNA with the Siberian Neanderthal that didn’t exist in the Western Neanderthal.

MELISSA: They thought there must be some mistake because there is no time when Africans and Neanderthals were known to have been in the same place where they could have interbred.

JORDAN: Now it’s important to note no one has ever detected this mix before… and the method was suggesting this event happened as recently as 100 to 150 thousands years ago. Anthropologists… geneticists… everyone working on this research was baffled. So they tried a method for understanding population histories… which did confirm a mixture event from African individuals into this Siberian Neanderthal… but there was a problem. The method could only look at sections of the genome. They needed more proof. That’s when Melissa was brought in with her method… ARGweaver.

MELISSA: It’s able to estimate the tree that sort of describes the relationship between a bunch of individuals at every single position in the genome and that the tree changes as you look across the genome. But if you look at the patterns of these trees you can see there are places where the Siberian Neanderthal is more closely related to Africans than we would expect.

MELISSA: our best hypothesis to how this could have happened is that there was actually a migration of individuals from out of Africa one-hundred and fifty-thousand years ago into the Middle East that then interbred with Neanderthals and subsequently died out.

JORDAN: So this is where my inner anthropologist gets a little carried away. What was it like for these groups to breed? Were the children of humans and Neanderthals treated like part of the community? Did they have families? When I asked Melissa about it… she was just as excited as I was about the implications of her research in answering these questions. But she admitted the answers probably won’t be found in genetic research. However…

MELISSA: One thing that we might be able to track down genetics that’s a big question is whether the hybrids were always females because a lot of times when the speciation is started, hybrid males don’t survive so I think as we get more data, we might be able to disentangle that and that would tell us a lot. Like if they were only females then we would sort of really get the impression that these really were different species.

JORDAN: But she says humans are just one example.

MELISSA: I wonder if speciation is always this messy in other animals, what other ways these interbreeding back and forth… I’m really interested in applying these methods to other species and sort of trying to understand general rules by which speciation occurs.

JORDAN: So what can this research do for us today? For one… it could aid in animal conservation efforts.

MELISSA: When do you decide that we need to protect this population, that population or can we treat them as one species… there’s a lot of people who already work on these questions and it’s really important but I’m really interested in them and I hope that my research can contribute to that.”)

JORDAN: So how can a method like ARGweaver change anthropological research… or even general research as a whole?

MELISSA: It adds another dimension to anthropology that used to rely only on fossil data and now we have all this genetic data that can tell us a lot more. It can’t tell us about people who didn’t breed so only the genetic winners are contributing to this angle, this story. But even in this case, we have a failed migration out of Africa because they bread with Neanderthal and left some genes in the Neanderthal we were able to learn about them. So as long as they pass on some genes… we might be able to learn about them. And I know the fossil record is very incomplete. There are some places where fossils don’t survive very well so it’s able to fill in some of those gaps in our knowledge.

JORDAN: So what’s next for Melissa… ARGweaver… and the research? A little refinement.

MELISSA: We haven’t been able to sort of delve deeply into particularly which genes the Neanderthals got from humans and whether there is any signs of selection or of high breeding compatibilities so we hope to sort of map the genes more carefully in the future and I think I’ll probably be involved with that study.

JORDAN: That’s geneticist Melissa Hubisz… a graduate student at Cornell University and an author of the paper… “Ancient gene flow from early modern humans into Easter Neanderthals…” which came out in the Spring of 2016 in the journal Nature. I’m Jordan D’Eri… co-editor of the National Science Foundation’s Science three-sixty news service… and writer… editor and co-host of the N-S-F Science three-sixty super science show… here at the National Science Foundation.

If you have any super cool N-S-F-funded archaeology or paleontology-themed research you think I would dig… send it along to Jordan D’Eri… that’s me… at jderi at N-S-F dot gov. That’s j d-e-r-i at N-S-F dot gov. And to finally bring it all home… here’s a fun fact you can dig: The name Neanderthal comes from the Neander valley in Germany… where some of the first Neanderthal bones were found. Coincidentally… “Neander” in Greek means “New Man.” That’s all for Dig This!