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Hawaiian genetic study shows 2-1 Asian-Melanesian admixture in Polynesians

Queen Liliuokalani of Hawaii in her youth

Native Hawaiians still make up some 38% of the population of Hawaii but most of them have mixed ancestry nowadays. This new study may help to understand them better and also includes some interesting findings about the overall origins of Polynesians, whose Melanesian ancestry is revealed as very significant.

Sung K. Kim et al., Population Genetic Structure and Origins of Native Hawaiians in the Multiethnic Cohort Study. PLoS ONE 2012. Open access ··> LINK [doi:10.1371/journal.pone.0047881]

Abstract

The population genetic structure of Native Hawaiians has yet to be comprehensively studied, and the ancestral origins of Polynesians remain in question. In this study, we utilized high-resolution genome-wide SNP data and mitochondrial genomes of 148 and 160 Native Hawaiians, respectively, to characterize their population structure of the nuclear and mitochondrial genomes, ancestral origins, and population expansion. Native Hawaiians, who self-reported full Native Hawaiian heritage, demonstrated 78% Native Hawaiian, 11.5% European, and 7.8% Asian ancestry with 99% belonging to the B4 mitochondrial haplogroup. The estimated proportions of Native Hawaiian ancestry for those who reported mixed ancestry (i.e. 75% and 50% Native Hawaiian heritage) were found to be consistent with their self-reported heritage. A significant proportion of Melanesian ancestry (mean = 32%) was estimated in 100% self-reported Native Hawaiians in an ADMIXTURE analysis of Asian, Melanesian, and Native Hawaiian populations of K = 2, where K denotes the number of ancestral populations. This notable proportion of Melanesian admixture supports the “Slow-Boat” model of migration of ancestral Polynesian populations from East Asia to the Pacific Islands. In addition, approximately 1,300 years ago a single, strong expansion of the Native Hawaiian population was estimated. By providing important insight into the underlying population structure of Native Hawaiians, this study lays the foundation for future genetic association studies of this U.S. minority population.

In my understanding, the most interesting elements from this study are the ADMIXTURE analyses:

Figure 1. ADMIXTURE clustering of Native Hawaiians for K = 5 (A) and K = 6 (B). Figures 1A and 1B illustrate the clustering of Native Hawaiians and HGDP samples based on GWAS data.

As the general Admixture analysis was not really conclusive about the Melanesian and Asian affinities of Native Hawaiians, the authors also performed a supervised K=2 analysis:

Figure 4. Supervised ADMIXTURE results for K = 2…
This appears to show rather unmistakably that Hawaiians (and by extension surely also other Polynesians, very close in genetics and history across the Pacific Ocean) have an important amount of Melanesian genetics, consistent with the “Slow Boat” model and the relevance of Melanesian Y-DNA haplogroup C2a among all Polynesian populations.
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