Mitochondrial DNA diversity of present-day Aboriginal Australians and implications for human evolution in Oceania.

Aboriginal Australians are one of the more poorly studied populations from the standpoint of human evolution and genetic diversity. Thus, to investigate their genetic diversity, the possible date of their ancestors' arrival and their relationships with neighboring populations, we analyzed mitochondrial DNA (mtDNA) diversity in a large sample of Aboriginal Australians. Selected mtDNA single-nucleotide polymorphisms and the hypervariable segment haplotypes were analyzed in 594 Aboriginal Australians drawn from locations across the continent, chiefly from regions not previously sampled. Most (~78%) samples could be assigned to mtDNA haplogroups indigenous to Australia. The indigenous haplogroups were all ancient (with estimated ages >40 000 years) and geographically widespread across the continent. The most common haplogroup was P (44%) followed by S (23%) and M42a (9%). There was some geographic structure at the haplotype level. The estimated ages of the indigenous haplogroups range from 39 000 to 55 000 years, dates that fit well with the estimated date of colonization of Australia based on archeological evidence (~47 000 years ago). The distribution of mtDNA haplogroups in Australia and New Guinea supports the hypothesis that the ancestors of Aboriginal Australians entered Sahul through at least two entry points. The mtDNA data give no support to the hypothesis of secondary gene flow into Australia during the Holocene, but instead suggest long-term isolation of the continent.

Antiquity and diversity of aboriginal Australian Y-chromosomes.

OBJECTIVE: Understanding the origins of Aboriginal Australians is crucial in reconstructing the evolution and spread of Homo sapiens as evidence suggests they represent the descendants of the earliest group to leave Africa. This study analyzed a large sample of Y-chromosomes to answer questions relating to the migration routes of their ancestors, the age of Y-haplogroups, date of colonization, as well as the extent of male-specific variation. METHODS: Knowledge of Y-chromosome variation among Aboriginal Australians is extremely limited. This study examined Y-SNP and Y-STR variation among 657 self-declared Aboriginal males from locations across the continent. 17 Y-STR loci and 47 Y-SNPs spanning the Y-chromosome phylogeny were typed in total. RESULTS: The proportion of non-indigenous Y-chromosomes of assumed Eurasian origin was high, at 56%. Y lineages of indigenous Sahul origin belonged to haplogroups C-M130*(xM8,M38,M217,M347) (1%), C-M347 (19%), K-M526*(xM147,P308,P79,P261,P256,M231,M175,M45,P202) (12%), S-P308 (12%), and M-M186 (0.9%). Haplogroups C-M347, K-M526*, and S-P308 are Aboriginal Australian-specific. Dating of C-M347, K-M526*, and S-P308 indicates that all are at least 40,000 years old, confirming their long-term presence in Australia. Haplogroup C-M347 comprised at least three sub-haplogroups: C-DYS390.1del, C-M210, and the unresolved paragroup C-M347*(xDYS390.1del,M210). CONCLUSIONS: There was some geographic structure to the Y-haplogroup variation, but most haplogroups were present throughout Australia. The age of the Australian-specific Y-haplogroups suggests New Guineans and Aboriginal Australians have been isolated for over 30,000 years, supporting findings based on mitochondrial DNA data. Our data support the hypothesis of more than one route (via New Guinea) for males entering Sahul some 50,000 years ago and give no support for colonization events during the Holocene, from either India or elsewhere.