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Homo sapiens and Neanderthals may have interbred, new research shows


About eight years ago, scientists began digging under a medieval castle in Germany. There, 24 feet underground, they discovered something intriguing - arrowheads, human bones and traces of reindeer, cave bears and woolly rhinoceroses. Together, the researchers concluded that the evidence showed that Homo sapiens were living at the same time as Neanderthals. Three papers from the dig have just been published, and Elena Zavala is co-author on all three of them. She's a postdoctorate researcher at the University of California, Berkeley. Elena, thanks for coming on the show.

ELENA ZAVALA: Thank you for having me.

NADWORNY: If I have this right, humans didn't come after Neanderthals. Instead, the two species coexisted, right?

ZAVALA: Right. So, from previous research, we do know that they've intermixed at least once or a couple of times because we have Neanderthal DNA within our own genomes. But there was always this question as to how often or for how long. And this current study finds that humans made it to the northern parts of Germany much earlier than we previously thought. And so this means that there was a much longer overlap than we had thought before.

NADWORNY: So tell me a little bit about kind of what you found, the evidence that led to that idea.

ZAVALA: Right. So within this dig, and this was, as you mentioned, quite a long excavation with many different people from many different expertises who worked on this together. What we found after several years was a few skeletal remains that with proteomic analysis, showed us that they were some type of hominin. And that, of course, made us very excited because we had this question as to were the stone tools that were found there at the site - were they made by humans, or were they made by Neanderthals? And we didn't know. And so that's where I got involved and performed genetic analysis on these skeletal fragments. And we found out that they were indeed humans or Homo sapiens. And the next question, of course, was the time period. How old were these remains? And Helen Fewlass is the one who performed the radiocarbon dating. And she found that these remains ranged all the way back to around 47,000 years.


ZAVALA: Yeah, it was incredible. And a wonderful surprise, as this really changes our idea of how quickly Homo sapiens made it to this part of Europe.

NADWORNY: I take it that scientists were surprised that humans survived so far north when the climate was so cold. Is that why we're surprised?

ZAVALA: Exactly. So previously, we had thought that part of the expansion of Homo sapiens up through Europe had to do with climatic change to warmer temperatures, and that past Homo sapiens followed these warmer temperatures north. But now we know that actually during this time period in this area, it was actually very cold. It was colder than it is now, and still Homo sapiens were present. And so that changes our whole idea about our ability to adapt to these temperatures and to journey through them. And yes, this opens up a whole new area.

NADWORNY: How about interbreeding between Neanderthals and Homo sapiens?

ZAVALA: So we do know, because we have Neanderthal DNA in our genomes today, or at least everyone outside of Africa has some Neanderthal DNA in them. We know that we met with Neanderthals at some point. How often that happened - still an area of active research and debate, but this new evidence really expands the period of time in which these exchanges could have happened.

NADWORNY: So a lot of questions remain.

ZAVALA: (Laughter) Yes, which is what makes this all exciting still.

NADWORNY: (Laughter) Wonderful. Elena Zavala is a postdoctorate researcher at the University of California, Berkeley, and one of the scientists that discovered Homo sapiens and Neanderthals living at the same time. Thanks so much for being with us.

ZAVALA: Thanks for having me. Transcript provided by NPR, Copyright NPR.

NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.

Elissa Nadworny reports on all things college for NPR, following big stories like unprecedented enrollment declines, college affordability, the student debt crisis and workforce training. During the 2020-2021 academic year, she traveled to dozens of campuses to document what it was like to reopen during the coronavirus pandemic. Her work has won several awards including a 2020 Gracie Award for a story about student parents in college, a 2018 James Beard Award for a story about the Chinese-American population in the Mississippi Delta and a 2017 Edward R. Murrow Award for excellence in innovation.