Modern humans from Africa have likely mated with Neanderthals when they migrated to the Eurasian continent thousands of years ago.

Findings of the studies published in the journals Nature and Science Jan.29 suggest that modern humans did not just rub elbows with the Neanderthals when they left Africa some 60,000 years ago. They two species of human may have produced offsprings which explains why humans today have Neanderthal DNA albeit remnants of these genes are more pronounced in those who have European and East Asian descent.

Neanderthal DNA makes up about 1 to 4 percent of the genomes of people who live outside of Africa and while this may appear modest, it still plays important genetic roles in humans today. These genes, for instance, affect the structures of our skin and hair and may have allowed us to survive cold weather.

The Neanderthal DNA may have provided our skin and hair the necessary toughness and insulation needed to weather the cold. "It seems quite compelling that as modern humans left Africa, met Neanderthals, and exchanged genes, we picked up adaptive variants in some genes that conferred an advantage in local climatic conditions," said Joshua Akey, an associate professor at the University of Washington in Seattle, who led the study in Science.

Sriram Sankararaman, of Harvard Medical School who co-authored the Nature study said that the Neanderthal DNA may have helped our ancestors survive in harsher environments that they were not accustomed to. "Neanderthals had been in these environments for hundreds or thousands of years," said Sankararaman. "As modern human ancestors moved into these areas, one way to quickly adapt would be to get genes from the Neanderthals."

Neanderthal genes can be a bane as well. Lineage from our big-browed ancestors can be responsible for a number of diseases that continue to afflict us today. Sankararaman said that variants of Neanderthal genes can increase one's risks for diseases such as lupus, biliary cirrhosis, Crohn's disease and type 2 diabetes.

"Now that we can estimate the probability that a particular genetic variant arose from Neanderthals, we can begin to understand how that inherited DNA affects us," said David Reich, a professor of genetics at Harvard Medical School who worked on the Nature paper. "We may also learn more about what Neanderthals themselves were like."