Early Homo sapiens interbred with Neanderthals, Denisovans; increased immunity to pathogens

It has already been established that a part of the modern human population, particularly Eurasians, carriies Neanderthal DNA. But early humans also interbred with other hominids like the Denisovans.

A study titled "Excavating Neandertal and Denisovan DNA from the genomes of Melanesian individuals" published in Science Mag indicates that Melanesian people have both Neanderthal and Denisovan ancestry.

"For much of human history, modern humans overlapped in time and space with other hominins. Analyses of the Neandertal and Denisovan genomes revealed that gene flow occurred between these archaic hominins and the ancestors of modern humans," the study reads. "Consequently, all non-African populations derive ~2% of their ancestry from Neandertals, whereas substantial levels of Denisovan ancestry (~2-4%) are only found in Oceanic populations, although low levels of Denisovan ancestry may be more widespread."

A report by CNN says that the interbreeding between Homo species helped strengthen the immune system of human ancestors.

"Many of these genes are involved in immunity and likely helped our ancestors fight new pathogens that they were exposed to as they dispersed into new environments," evolutionary geneticist Joshua Akey told CNN. 

And while scientists have already established that anatomically modern Homo sapiens and Homo neanderthalensis interbred, it might have happened much earlier than initially thought.

It was previously believed that humans and Neanderthals mingled around 60,000 years ago, but according to a report by the BBC, parts of human DNA were found in the genome a female Neanderthal, the remains of which were discovered in the Siberian Altai Mountains. This indicates that interbreeding took places as far back as 100,000 years ago.

Dr Sergi Castellano of Max Planck Institute for Evolutionary Anthropology, said, "It is significant for understanding the history of modern humans and Neanderthals."

The institute in Germany coordinates the Neanderthal genome project.