Mitochondrial diversity in human head louse populations across the Americas.

Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico D.F., MexicoKEY WORDS human parasites; mitochondrial DNA; New World; migrations; human liceABSTRACT Anthropological studies suggest that thegenetic makeup of human populations in the Americasis the result of diverse processes including the initial col-onization of the continent by the first people plus post-1492 European migrations. Because of the recent natureof some of these events, understanding the geographicalorigin of American human diversity is challenging. How-ever, human parasites have faster evolutionary ratesand larger population sizes allowing them to maintaingreater levels of genetic diversity than their hosts. Thus,we can use human parasites to provide insights intosome aspects of human evolution that may be unclearfrom direct evidence. In this study, we analyzed mito-chondrial DNA (mtDNA) sequences from 450 head licein the Americas. Haplotypes clustered into two well-supported haplogroups, known as A and B. Haplogroupfrequencies differ significantly among North, Centraland South America. Within each haplogroup, we foundevidence of demographic expansions around 16,000 and20,000 years ago, which correspond broadly with thoseestimated for Native Americans. The parallel timing ofdemographic expansions of human lice and NativeAmericans plus the contrasting pattern between the dis-tribution of haplogroups A and B through the Americassuggests that human lice can provide additional evi-dence about the human colonization of the New World.Am J Phys Anthropol 152:118-129, 2013.