HomeScienceStudy: Much of Neanderthal-Modern Human Interbreeding Took Place in Near East

Study: Much of Neanderthal-Modern Human Interbreeding Took Place in Near East


Studies of human fossils, and the DNA extracted from them, reveal a complex history of interbreeding between various human lineages over the past 100,000 years. Of particular interest is the nature of the population interactions between the Neanderthals of Ice Age Europe and western Asia and anatomically modern Homo sapiens that eventually replaced them. In a new study, a team of scientists from the United States and South Africa used six measurements of the facial skeleton, in samples of Neanderthal and early modern human fossils, in an exploratory study aimed at trying to identify geographic regions — from the Near East to western Europe — where interbreeding may have been prevalent enough to have left a signal in the facial morphology of the early modern humans of those regions.

Neanderthal man. Image credit: Mauro Cutrona.

Neanderthal man. Image credit: Mauro Cutrona.

“Ancient DNA caused a revolution in how we think about human evolution,” said Professor Steven Churchill, an evolutionary anthropologist in the Department of Evolutionary Anthropology at Duke University and the Centre for the Exploration of the Deep Human Journey at the University of the Witwatersrand.

“We often think of evolution as branches on a tree, and researchers have spent a lot of time trying to trace back the path that led to us, Homo sapiens.”

“But we’re now beginning to understand that it isn’t a tree — it’s more like a series of streams that converge and diverge at multiple points.”

“Our work here gives us a deeper understanding of where those streams came together,” said Professor Ann Ross, a biologist in the Department of Biological Sciences at North Carolina State University.

“We know there was interbreeding. Modern Asian populations seem to have more Neanderthal DNA than modern European populations, which is weird — because Neanderthals lived in what is now Europe,” Professor Churchill said.

“That has suggested that Neanderthals interbred with what are now modern humans as our prehistoric ancestors left Africa, but before spreading to Asia.”

“Our goal with this study was to see what additional light we could shed on this by assessing the facial structure of prehistoric humans and Neanderthals.”

“By evaluating facial morphology, we can trace how populations moved and interacted over time,” Professor Ross said.

“And the evidence shows us that the Near East was an important crossroads, both geographically and in the context of human evolution.”

In their research, the authors collected data on craniofacial morphology from the published literature. This ultimately resulted in a data set including 13 Neanderthals, 233 prehistoric and 83 modern Homo sapiens.

The researchers focused on standard craniofacial measurements, which are reproducible, and used those measurements to assess the size and shape of key facial structures.

They performed an in-depth analysis to determine whether a given human population was likely to have interbred with Neanderthal populations, as well as the extent of that likely interbreeding.

“Neanderthals had big faces. But size alone doesn’t establish any genetic link between a human population and Neanderthal populations. Our work here involved a more robust analysis of the facial structures,” Professor Churchill said.

The team also accounted for environmental variables that are associated with changes in human facial characteristics, to determine the likelihood that connections they established between Neanderthal and human populations 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 likely genetic influences,” Professor Ross said.

“We also found that facial shape was a more useful variable for tracking the influence of Neanderthal interbreeding in human populations over time. Neanderthals were just bigger than humans.”

“Over time, the size of human faces became smaller, generations after they had bred with Neanderthals. But the actual shape of some facial features retained evidence of interbreeding with Neanderthals.”

The results were published this month in the journal Biology.


Steven E. Churchill et al. 2022. Midfacial Morphology and Neandertal-Modern Human Interbreeding. Biology 11 (8): 1163; doi: 10.3390/biology11081163


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