​New York, Nov 13 (IANS) Thousands of years ago, when the ancestors of modern humans made their way out of Africa to other parts of the globe, their encounter with Neanderthals and Denisovans helped the human race over the years, researchers have said.

Ancient humans met up -- and in some cases had children with -- other forms of humans, including the Neanderthals and Denisovans. This was found through the traces of those meetings remaining in the human genome.

"Our work shows that hybridisation 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," Joshua Akey of University of Washington said in a statement.

The researchers used genome-scale maps of Neanderthal and Denisovan sequences identified in more than 1,500 geographically diverse people.

The researchers were searching for archaic DNA sequences in those human genomes at frequencies much higher than would be expected if those genes were not doing people any good.

While the vast majority of surviving Neanderthal and Denisovan sequences are found at relatively low frequencies (typically less than five per cent), the new analyses turned up 126 places in our genomes where these archaic sequences exist at much higher frequencies, reaching up to about 65 per cent. 

Seven of those regions were found in parts of the genome known to play a role in characteristics of our skin. Another 31 are involved in immunity.

"The ability to increase to such high population frequencies was most likely facilitated because these sequences were advantageous," Akey explains in paper published in the journal Current Biology.