A segment of the human X chromosome found in non-African human populations comes from Neandertals, report the Université de Montréal's Damian Labuda and his colleagues in this month's Molecular Biology and Evolution. This small section, the researchers say, is found in about 9 percent of non-Africans. Labuda and his team analyzed 6,092 X chromosomes from populations across the world and found evidence of admixture between Neandertals and humans as they migrated out of Africa.