When Homo sapiens first expanded out of Africa, they found a world filled with challenges that our species had never encountered before, including winter. A new study confirms that part of the reason our ancestors were able to conquer the planet so quickly was that related species had forged a path. A few mating encounters were all it took to gift us the hard-won genes that assisted our expansion.
People whose ancestry lies in continents other than Africa have up to 6 percent of their genes from Neanderthals and Denisovans, along with a mysterious fourth species of which we know little. This legacy is particularly common in parts of the genome associated with the immune system. Not all our DNA is equally important, however, and geneticists have debated how much these haplotypes, or genes with a common origin, mattered in our rapid spread to every corner of the planet.
Professor Joshua Akey of the University of Washington claims to have answered this question in Current Biology. "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 said in a statement.
Recently, the genome sequences of 1,523 people of European, Asian, and Melanesian descent have been mapped for their Neanderthal and Denisovan genetic inheritance. Akey searched this database for haplotypes that have become so common, their frequency can only be explained if they confer an evolutionary advantage.