Deep haplotype divergence and long-range linkage disequilibrium at xp21.1 provide evidence that humans descend from a structured ancestral population.
Fossil evidence links human ancestry with populations that evolved from modern gracile morphology in Africa 130,000-160,000 years ago. Yet fossils alone do not provide clear answers to the question of whether the ancestors of all modern Homo sapiens comprised a single African population or an amalgamation of distinct archaic populations. DNA sequence data have consistently supported a single-origin model in which anatomically modern Africans expanded and completely replaced all other archaic hominin populations. Aided by a novel experimental design, we present the first genetic evidence that statistically rejects the null hypothesis that our species descends from a single, historically panmictic population. In a global sample of 42 X chromosomes, two African individuals carry a lineage of noncoding 17.5-kb sequence that has survived for >1 million years without any clear traces of ongoing recombination with other lineages at this locus. These patterns of deep haplotype divergence and long-range linkage disequilibrium are best explained by a prolonged period of ancestral population subdivision followed by relatively recent interbreeding. This inference supports human evolution models that incorporate admixture between divergent African branches of the genus Homo.
Garrigan
Daniel
D
Genomic Analysis and Technology Core, University of Arizona, Tucson, Arizona 85721, USA.
Mobasher
Zahra
Z
Kingan
Sarah B
SB
Wilder
Jason A
JA
Hammer
Michael F
MF
D005075:Biological Evolution; D041321:Chromosomes, Human, X; D005580:Fossils; D005828:Genetics, Population; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium