Independent histories of human y chromosomes from melanesia and Australia

To investigate the origins and relationships of Australian and Melanesian p opulations, 611 males from 18 populations from Australia, Melanesia, and ea stern/southeastern Asia were typed for eight single-nucleotide polymorphism (SNP) loci and seven short tandem-repeat loci on the Y chromosome. A uniqu e haplotype, DYS330.1del/RPS4Y711T, was found at a frequency of 53%-69% in Australian populations, whereas the major haplotypes found in Melanesian po pulations (M4G/M5T/M9G and DYS390.3del/RPS4Y711T) are absent from the Austr alian populations. The Y-chromosome data thus indicate independent historie s for Australians and Melanesians, a finding that is in agreement with evid ence from mtDNA but that contradicts some analyses of autosomal loci, which show a close relationship between Australian and Melanesian (specifically, highland Papua New Guinean) populations. Since the Australian and New Guin ean landmasses were connected when first colonized by humans greater than o r equal to 50,000 years ago but separated some 8,000 years ago, a possible way to reconcile all the genetic data is to infer that the Y-chromosome and mtDNA results reflect the past 8,000 years of independent history for Aust ralia and New Guinea, whereas the autosomal loci reflect the long preceding period of common origin and shared history. Two Y-chromosome haplotypes (M 119C/M9G and M122C/M9G) that originated in eastern/southeastern Asia are pr esent in coastal and island Melanesia but are rare or absent in both Austra lia and highland Papua New Guinea. This distribution, along with demographi c analyses indicating that population expansions for both haplotypes began similar to4,000-6,000 years ago, suggests that these haplotypes were brough t to Melanesia by the Austronesian expansion. Most of the populations in th is study were previously typed for mtDNA SNPs; population differentiation i s greater for the Y chromosome than for mtDNA and is significantly correlat ed with geographic distance, a finding in agreement with results of similar analyses of European populations.