The benefits of hybridization
Crossing Homo sapiens with Neanderthals could lead to human evolutionary advantages
Anna Novikovskaya, Naked Science
Previously, scientists believed that the evolutionary success of modern homo sapiens led to the complete replacement of archaic human species with a new, more competitive species that secured an advantage due to complex behavioral adaptations. However, recent studies have shown that in fact the process of Homo sapiens becoming the "king of nature" was somewhat more complicated.
There is growing evidence that ancient human lineages, such as Neanderthals, were not absolute savages, only slightly different from monkeys: they took care of old and infirm tribesmen, created drawings and art objects, decorated themselves with bird feathers.
Now, it seems, the old myth of replacing archaic types of people with a new one will be finally dispelled. A new study (Harvati & Ackermann, Merging morphological and genetic evidence to assess hybridization in Western Eurasian late Pleistocene hominins // Nature Ecology & Evolution) has shown that a modern-type person repeatedly interbred with ancient people, and the change of species occurred not so much through competitive substitution as through partial substitution with assimilation.
To collect this data, scientists had to try: ancient DNA is rarely preserved in fossil samples, so it is mainly necessary to identify possible hybrids by skeletons. Having collected a large number of fossils of ancient people from the Upper Paleolithic of Eurasia, dating from about 20-40 thousand years ago, scientists examined the preserved DNA fragments and analyzed the shape of the skulls, comparing it with the skulls of Neanderthals who lived before the arrival of Homo sapiens in Europe, and African skulls of Homo sapiens.
The researchers paid special attention to three areas of the skull: the lower jaw, the cranium and the face, where they looked for characteristic signs of hybridization, such as anomalies of teeth or unusual sizes. These traits are still characteristic of many interspecific mammalian hybrids, including primates.
It turned out that hybrids of Neanderthals and modern humans lived not only in the Middle East — the place of contact of the two species — but also in Western and Eastern Europe. Unfortunately, not all the remains have been preserved well enough to be able to conduct a full genomic analysis and determine the degree of hybridization, but the authors hope that their work will encourage researchers to study these fossils more closely and combine several lines of evidence to finally establish the fact of hybridization.
Interspecific interbreeding is known in ten percent of modern animal species, including hornbills, bears, canids and primates. Since hybridization leads to the emergence of new genome variants by shuffling the genes of the parent species, this can contribute to extremely rapid evolution, especially when faced with new or changing environmental conditions.
Thus, hybridization may have endowed ancient humans with genetic and anatomical features that gave them important advantages when spreading from Africa around the world, which led to the emergence of a physically diverse and evolutionarily stable modern man.
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