Climate Change, Habitat Expansion Allowed Interbreeding Between Neanderthals and Denisovans, DNA Study Reveals

According to a new study, climate change and habitat expansion brought Neanderthals and Denisovans together, which led to interbreeding.

Extreme Climate Change and Habitat Expansion

According to recent research, Neanderthals and Denisovans were able to procreate with one another hundreds of thousands of years ago due to alterations in the Earth's orbit around the Sun. The authors of the paper claim that these changes in the cosmic trajectory allowed for significant temperature changes on Earth, which allowed for the expansion of the ancestors' habitats and their eventual meeting.

It is common knowledge that in the distant past, numerous human species were able to interbreed. Neanderthal genes make up about 2% of the DNA of non-African groups, whereas people from Southeast Asia, as well as Oceania, share up to 5% of their genome with Denisovans. These ancient sexual arrangements have left their mark on present human genomes.

Interbreeding Hominin

Researchers discovered the 90,000-year-old remains of a daughter who had a Neanderthal mother and a Denisovan father in Siberia's renowned Denisova Cave.

The age and location of 22 Denisovan items and 773 Neanderthal remains were examined by the study's authors in order to pinpoint when, where, and how both of these extinct human species were able to interbreed. The researchers were able to chart the historical distribution patterns of both hominid lineages by combining these patterns with genetic information and supercomputer models of the ancient environment.

According to the authors, Denisovans had a more expansive niche space than Neanderthals since they lived in hot, humid climes. Denisovans lived in both boreal forests and tundra, although Neanderthals were more prevalent in temperate woodlands.

This indicates that their preferred habitats were geographically distinct, with Neanderthals often favoring southern Eurasia and Denisovans the northeast, according to research author Jiaoyang Ruan.

However, fluctuations in carbon dioxide levels led to significant alterations in vegetation cover over the Northern Hemisphere during warm interglacial periods, when Earth's orbit around the Sun came to be more elliptic and temperatures rose. As a result, temperate forests spread eastward, opening up routes for Neanderthals to enter Denisovan land.

According to Ruan, it appears as though the glacial and interglacial temperature changes set the backdrop for exceptional and enduring relationships, the genetic remnants of which are still present now.

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Ancient Romance and Archaic Humans

In order to recreate this prehistoric romance, the researchers located contact areas in the Caucasus, central Eurasia, as well as the mountain ranges of Tianshan and Changbai.

In the Siberian Altai, for example, Denisovans and Neanderthals showed a high possibility of communication, primarily during interglacial periods, according to scientists. Genetic evidence suggests at least six independent occurrences of interbreeding involving the two species are supported by this data.

Five of these may be traced by the researchers to central-southern Siberia between 130,000 and 80,000 years ago. They claim that the sixth probably took place in Eastern Europe a little earlier than this.

Overall, according to the study's authors, the results show how glacial-interglacial temperature changes probably had a significant role in promoting gene exchange between ancient humans.