Interbreeding with Neanderthals, Denisovans Helped Ancient Human Ancestors to Survive Outside Africa

A new study revealed that the ancestors of modern humans who went out of Africa interacted and interbred with other forms of early humans, such as Neanderthals and Denisovans. This interbreeding helped our ancestors to develop various traits for survival.

According to a study published in the journal Current Biology, certain traits in modern humans, such as the immune system and skin, can be attributed to the interbreeding with Neanderthals and Denisovans. These traits were identified from 126 different places in the human genome that is still present in modern humans.

The study revealed that about 2 percent of non-African individuals inhereted their ancestry from Neanderthals. Meanwhile, those with Melanesian ancestry had about 2 to 4 percent of their genomes from Denisovans.

The team came up with these results by using the recently constructed genome-scale maps of Neanderthal and Denisovan sequences found in early humans around the globe, such as East Asia, Europe and South Asia, 1,500 years ago. The scientists also analyzed genomes from Melanesia, which is now comprised of Indonesia, New Guinea, Fiji and Vanuatu.

The abovementioned 126 places in the human genomes were revealed to have contained about 65 percent frequency of archaic DNA sequences, most of which were found in areas involving skin characteristics and immunity.

"The ability to increase to such high population frequencies was most likely facilitated because these sequences were advantageous. In addition, many of the high-frequency sequences span genes involved in the immune system, which is a frequent target of adaptive evolution," said Joshua Akey of University of Washington School of Medicine in Seattle via Science Daily.

The study further explained that the discovery shows that the inherited genes from Neanderthals and Devinosans played an important role in human adaptation and interaction with the environment.

"Our work shows that hybridization was not just some curious side note to human history, but had important consequences and contributed to our ancestors' ability to adapt to different environments as they dispersed throughout the world," Akey concluded.