Genomic insights into the human population history of Australia and New Guinea
The ancient continent of Sahul, encompassing Australia, New Guinea and Tasmania, contains some of the earliest archaeological evidence for humans outside of Africa, dating back to at least 50 thousand years ago (kya). New Guinea was also one of the sites were humans developed agriculture in the last 10 thousand years. Despite the importance of this part of the world to the history of humanity outside Africa, little is known about the population history of the people living here. In this thesis I present population-genetic studies using whole-genome sequencing and genotype array datasets from more than 500 indigenous individuals from Australia and New Guinea, as well as initial work on large-scale sequencing of other, worldwide, human populations in the Human Genome Diversity Project panel. Other than recent admixture after European colonization of Australia, and Southeast Asian ad- mixture in the lowlands of New Guinea in the last few millennia, the populations of Sahul appear to have been genetically independent from the rest of the world since their divergence ∼50 kya. There is no evidence for South Asian gene flow to Australia, as previously suggested, and the highlands of Papua New Guinea (PNG) have remained unaffected by non-New Guinean gene flow until the present day. Despite Sahul being a single connected landmass until ∼8 kya, different groups across Australia are nearly equally related to Papuans, and vice versa, and the two appear to have separated genetically already ∼30 kya. In PNG, all highlanders strikingly appear to form a clade relative to lowlanders, and population structure seems to have been reshaped, with major population size increases, on the same timescale as the spread of agriculture. However, present- day genetic differentiation between groups is much stronger in PNG than in other parts of the world that have also transitioned to agriculture, demonstrating that such a lifestyle change does not necessarily lead to genetic homogenization. The results presented here provide detailed insights into the population history of Sahul, and sug- gests that its history can serve as an independent source of evidence for understanding human evolutionary trajectories, including the relationships between genetics, lifestyle, languages and culture.
Human genetics, Population genomics, Genome sequencing, Population history
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