Skull research sheds light on human-Neanderthal interbreeding

Deep within the genome of modern-day humans harbor trace amounts of DNA from a long-lost relative: the Neanderthal (homo neanderthalensis). They lived about 400,000 to 40,000 years ago, and are the closest extinct human to today’s humans (Gay spa). A body of research shows that Neanderthals interbred with humans about 100,000 years ago, and a new study published yesterday in the journal Biology This is building on our knowledge of where interbreeding took place.

“Ancient DNA revolutionized the way we think about human evolution,” study co-author Steven Churchill, professor of evolutionary anthropology at Duke University, said in a press release. “We often think of evolution as the branches of a tree, and researchers have spent a lot of time tracing the path that led us to Homo sapiens. But we’re now beginning to understand that it’s not a tree—it’s more like a series of streams that converge and diverge at many points.”

A team of researchers from North Carolina State University, Duke University and the University of the Witwatersrand in South Africa combined previously published data on Neanderthal craniofacial morphology, or facial structure. Neanderthals had larger faces than modern humans, but facial size is not sufficient to determine the genetic relationship between them and the human population.

A data set consisting of 13 Neanderthals, 233 prehistoric Homo sapiens, and 83 modern humans was constructed by the team from the available literature. They focused on standard skull measurements as a control to study the shape and size of key facial structures. Being a control allowed the team to determine whether Neanderthal populations and the extent of interbreeding with human populations were likely to be interrelated.

[Related: Ancient milk-drinkers were just fine with their lactose intolerance–until famine struck.]

The researchers also used environmental variables (such as climate) that are associated with changes in human facial features, to determine the likelihood that the connection between Neanderthal and human populations was the result of interbreeding rather than another factor.

“We found that we focused on facial features that were not affected by climate, which made it easier to identify potential genetic influences,” said Ann Ross, study author and professor of biological sciences at North Carolina State University. “We also found that face size was a more useful variable for tracking the effect of Neanderthal interbreeding on human populations over time. Neanderthals were larger than humans. Over time, human face size became smaller, after they interbred with Neanderthals. But the actual size of some facial features Evidence of interbreeding with Neanderthals remains.

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The next step in this type of study is to take measurements from more human populations, such as the Natufian culture that lived 11,000 years ago in the Mediterranean in what is now Israel, Jordan, and Syria. Their conclusions when comparing these skulls This supports the hypothesis that interbreeding occurred extensively in the region from North Africa to Iraq. “It was an exploratory study. And, to be honest, I wasn’t sure if this approach would really work—we had a relatively small sample size, and we didn’t have the data we wanted on facial structures. But, in the end, the results we got are really fascinating,” Churchill added.

“The picture is really complicated,” Churchill said. “We know there was interbreeding. Modern Asian populations seem to have more Neanderthal DNA than modern European populations, which is strange – because Neanderthals lived in what is now Europe. This suggests that Neanderthals interbred with modern humans as our prehistoric ancestors left Africa, But before spreading to Asia. Our goal with this study was to evaluate the facial structure of prehistoric humans and Neanderthals to see what more light we could shed on it.”

Neanderthals are known for making and using a wide range of sophisticated tools, controlling fire, living in shelters, making and wearing clothing, hunting large animals, and eating plants. There is also evidence that they buried their dead, a marker of sophistication for the species. The first complete genome of a Neanderthal was sequenced in 2010.

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