Study of ancient skulls sheds light on the interbreeding of humans with Neanderthals

An adult male Neanderthal. Reconstruction based on Shanidar 1 by John Gurche for Human Origins Program, NMNH. Credit: Chip Clark.

Research has proven that there are traces of Neanderthal DNA in the genome of modern humans. An exploratory study that evaluated the facial structure of prehistoric skulls now provides new insights, and supports the hypothesis that much of this intermarriage occurred in the Near East – the region that stretches from North Africa to Iraq.

Ancient DNA has revolutionized the way we think human evolutionSays Stephen Churchill, co-author of the study and professor of evolutionary anthropology at Duke University. “We often think of evolution as branches on a tree, and researchers have spent a lot of time trying to trace the path that led to us, Homo sapiens. But we’re now beginning to understand that it’s not a tree — it’s more like a series of streams converging and diverges at multiple points.”

“Our work here gives us a deeper understanding of where those currents come together,” says Ann Ross, study author and professor of biological sciences at North Carolina State University.

“The picture is really complicated,” Churchill says. “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 Neandertals interbred with what are now modern humans.” Like our prehistoric ancestors it left Africa, but before it spread to Asia. Our aim with this study was to see what additional light we can shed on this by evaluating the facial structure of prehistoric humans and Neanderthals.”

“By assessing facial morphology, we can track how populations move and interact over time,” Ross explains. “And the evidence shows us that the Near East was an important crossroads, both geographically and in the context of human evolution.”

In this study, researchers collected data on craniofacial morphology from the published literature. This eventually led to a data set that includes 13 Neanderthals, 233 prehistoric Homo sapiens, and 83 modern humans.

The researchers focused on standard craniofacial measurements, which are reproducible, and used those measurements to assess the size and shape of key facial structures. This then allowed the researchers to perform an in-depth analysis to determine if it was a particular human Population It is possible that they interbred with the primitive population, as well as the extent of this possible intermarriage.

“Neanderthals had big faces,” Churchill says. “But size alone does not establish any genetic link between A population and primitive inhabitants. Our work here included a more robust analysis of facial structures.”

The researchers also considered environmental variables associated with changes in human facial characteristics, to determine the possibility that the connections they made between Neanderthals and the population were the result of interbreeding rather than other factors.

“We found that the facial characteristics we focused on were not strongly influenced by climate, which made it easier to identify potential genetic influences,” Ross says. “We also found that face shape was a more useful variable for tracking the effect of Neanderthal crossbreeding on humans over time. Neanderthals were larger than humans. Over time, the size of human faces became smaller, generations after they interbred with Neanderthals. But the actual shape of some facial features is Keep evidence of interbreeding with Neanderthals.”

“This was an exploratory study,” Churchill says. “And frankly, I wasn’t sure if this approach actually worked – we had a relatively small sample size, and we didn’t have as much data on facial structures as we’d like. But, in the end, the results we got are really compelling.”

“To build on this, we would like to include measurements from more populations, such as the Natufians, who lived more than 11,000 years ago on the Mediterranean in what are now Israel, Jordan and Syria.”

The paper was published in biology.

The genomes of five late Neanderthals provide insight into the history of the Neanderthals

more information:
Stephen E. Churchill et al, Mid-face morphology and Neanderthal hybridization, biology (2022). DOI: 10.3390 / biology11081163

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