A PRE-COLUMBIAN Y-CHROMOSOME-SPECIFIC TRANSITION AND ITS IMPLICATIONSFOR HUMAN EVOLUTIONARY HISTORY

A polymorphic C --> T transition located on the human Y chromosome was found by the systematic comparative sequencing of Y-specific sequence -tagged sites by denaturing high-performance liquid chromatography. Th e results of genotyping representative global indigenous populations i ndicate that the locus is polymorphic exclusively within the Western H emisphere. The pre-Columbian T allele occurs at >90% frequency within the native South and Central American populations examined, while its occurrence in North America is approximate to 50%. Concomitant genotyp ing at the polymorphic tetranucleotide microsatellite DYS19 locus reve aled that the C --> T mutation displayed significant linkage disequili brium with the 186-bp allele, The data suggest a single origin of ling uistically diverse native Americans with subsequent haplotype differen tiation within radiating indigenous populations as well as post-Columb ian European and African gene flow, The mutation may have originated e ither in North America at a very early time during the expansion or be fore it, in the ancestral population(s) from which all Americans may h ave originated. The analysis of linkage of the DYS199 and the DYS19 te tranucleotide loci suggests that the C --> T mutation may have occurre d around 30,000 years ago, We estimate the nucleotide diversity over 4 .2 kb of the nonrecombining portion of the Y chromosome to be 0.00014. Compared to autosomes, the majority of variation is due to the smalle r effective population size of the Y chromosome rather than selective sweeps. There begins to emerge a pattern of pronounced geographical lo calization of Y-specific nucleotide substitution polymorphisms.