Neanderthals and modern humans interbred primarily in the Middle East

(ORDO NEWS) — Scientists have proposed an explanation for a long-standing mystery: why Asians have more Neanderthal genes than Europeans.

The study of the ancient DNA of Homo sapiens and their relatives reveals the complex path of interbreeding between different human species over the past hundred thousand years.

Of particular interest is the history of the relationship between the Ice Age Neanderthals in Europe and Western Asia and modern humans, who eventually replaced them.

The paper , published in the journal Biology , presents the results of a study of this issue by a group of scientists from the United States and South Africa.

They used six measurements of the facial part of the skull in Neanderthal and early modern humans fossils to identify geographic regions from the Near East to Western Europe where interbreeding between the two could be common enough to leave a mark on facial morphology.

Neanderthals and modern humans interbred primarily in the Middle East 2
Map of western Eurasia showing areas and estimated dates of possible hybridization between Neanderthals and modern humans (in red) based on fossil specimens from the indicated locations. The black dot marks Denisova Cave

According to the analysis of ancient DNA and its comparison with the DNA of our contemporaries, today’s Asian populations of people, on average, have more Neanderthal roots than European ones.

This looks strange: after all, Neanderthals lived mainly in Europe, in Asia their sites were found much less, and not east of Altai.

To explain this oddity, scientists have suggested that Neanderthals interbred with modern humans after our prehistoric ancestors left Africa, but before they arrived in Asia.

The researchers tried to confirm this hypothesis by studying the shape of the facial part of the skull of prehistoric Homo sapiens , Neanderthals and our contemporaries.

The authors of the work collected data on the morphology of the craniofacial region from the published literature. The result was a dataset that included 13 Neanderthals, 233 prehistoric, and 83 modern Homo sapiens .

They focused on standard, easily reproducible measurements of the craniofacial region. The researchers conducted an in-depth analysis to determine the likelihood and extent of this human population interbreeding with Neanderthal populations.

Neanderthals and modern humans interbred primarily in the Middle East 3
Skull points used to determine the presence of Neanderthal genes

“Neanderthals had big faces. But size alone does not establish a genetic link between the human population and Neanderthal populations. Our work included a more thorough analysis of facial structures,” said Steven Churchill, lead author of the work.

In addition to the morphological parameters themselves, the scientists took into account environmental variables associated with changes in the characteristics of the human face to determine the likelihood that the links they established between Neanderthal and human populations were the result of interbreeding, and not other factors.

In other words, they cut off those conditions (for example, a sharp decrease in the availability of food) that would equally affect the change and, as a result, the possible similarity of the faces of Neanderthals and Homo sapiens.

As a result, they found that most of the crossings took place in the Middle East: from North Africa to Iraq. And only then people who received Neanderthal genes began to explore Asia.

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