The genomic landscape of contemporary western Remote Oceanians

Abstract

The Vanuatu archipelago served as a gateway to Remote Oceania during one of the most extensive human migrations to uninhabited lands around 3,200 years ago. Ancient DNA studies suggest an initial settlement by East Asian-related peoples that was quickly followed by the arrival of Papuan-related populations, leading to a major population turnover. Yet, there is uncertainty over the population processes and the sociocultural factors that have shaped the genomic diversity of ni-Vanuatu, who present nowadays among the world's highest linguistic and cultural diversity. Here, we report genome-wide data for 1,433 contemporary ni-Vanuatu from 29 different islands, including 287 couples. We find that ni-Vanuatu derive their East Asian- and Papuan-related ancestry from the same source populations and descend from relatively synchronous admixture events that occurred around 1,700-2,300 years ago, indicating a peopling history common to all the archipelago. However, our analyses reveal that the Papuan population turnover was geographically uneven, and that the genetic contribution of Papuan-related peoples was male-biased. Furthermore, we detect Polynesian ancestry arriving around 600-1,000 years ago to South Vanuatu, and map its distribution to both Polynesian- and non-Polynesian-speaking islands. Lastly, we provide evidence for a tendency of spouses to carry similar genetic ancestry, when accounting for relatedness avoidance. The signal is not driven by strong genetic effects of specific loci or trait-associated variants, suggesting that it results instead from social assortative mating. Altogether, our findings provide insight into both the genetic history of ni-Vanuatu populations and how sociocultural processes have shaped the diversity of their genomes.

Genomic perspectives on human dispersals during the Holocene

“…However, an initial ancient DNA study surprisingly found that individuals from Vanuatu and Tonga, dating to ~2.5-2.9 kya, possessed little or no Papuan-related ancestry (118). Subsequent studies showed that Papuan-related ancestry spread later, via mostly male-mediated, continuous migration (97,120,121). Other studies suggested back migrations from Polynesia (121) and native American ancestry that arrived in Polynesia before European contact (122), although the latter relies on analyses of modern samples and so far has not received any support from ancient DNA (123).…”

“…Subsequent studies showed that Papuan-related ancestry spread later, via mostly male-mediated, continuous migration (97,120,121). Other studies suggested back migrations from Polynesia (121) and native American ancestry that arrived in Polynesia before European contact (122), although the latter relies on analyses of modern samples and so far has not received any support from ancient DNA (123). Overall, instead of the stereotypical view that settlement of Remote Oceania involved one-time, "sweepstakes"-like successes amidst a sea of failures, genetic data confirm archaeological evidence for multiple dispersals and large-scale trade networks throughout Remote Oceania, including repeated contact with Near Oceania (124).…”

The genomic footprint of social stratification in admixing American populations

“…Beyond analytical modelling, population genetics studies have also measured ancestry-related assortative mating through the correlation of genetic ancestry proportions between mates Bryc et al (2010); Korunes et al (2022); Arauna et al (2022 ) . Non-random mating can also be monitored through deviations of the observed heterozygosity from Hardy-Weinberg equilibrium expected values Crow and Felsenstein (1968 ) .…”