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Eвa
06-13-2018, 12:42 AM
Not much attention is given to Pacific Islanders on this forum and in general, so I thought I would fill you guys in with a comprehensive analysis on the population genomics of Pacific Islanders. There is tremendous amounts of genetic variation in this area that isn't paid much attention to. This is all based off of a 2008 study done on Pacific Islander populations, which I will leave a link to at the end of this post. I will essentially be paraphrasing interesting facts from the study that are important for discussion. The study examined around 1,500 individuals at 687 micro-satellites and 203 indel polymorphisms in the genome.

In order to understand the genetics behind the Pacific Islands, one must first understand the distinction between "Near Oceania" and "Remote Oceania."

- Near Oceania refers to the populations of Papua New Guinea and its Islands.
- Remote Oceania refers to the populations of Micronesian, Austronesian, and Polynesian islands.

Here is a map of Near vs. Remote Oceania:
https://www.researchgate.net/profile/Peter_Sheppard/publication/277143247/figure/fig1/AS:[email protected]/Map-of-Near-and-Remote-Oceania-and-the-Solomon-Islands-showing-the-distribution-of-the.png


Organization of Genetic Variation among Pacific Islanders (Near Oceania)

Within the Islands of Papua New Guinea, genetic variation seems to be correlated with Island size and topography. The larger the island, the more genetic variation there tends to be.

Genetic Variation Within and Among Populations (Near Oceania)

When it comes to Near Oceania, within population genetic variation is very low. This is likely due to group isolation and low rates of intermarriage. However, the among population genetic variation in different Melanesian populations is extremely substantial, and surpasses the amount of genetic variation among different European populations and different East Asian populations.


Genetic Variation Within and Among Populations (Remote Oceania)

Genetic variation in Remote Oceanian populations is remarkably low, both within and among populations. However, there are some genetic differences among the different populations. For example, the Maori of New Zealand have a significant amount of European ancestry (12%) and almost no Papuan or mainland East Asian ancestry at all, while the Samoans have about 5% European ancestry and 1/8 of their ancestry from various Papuan groups in New Ireland and New Britain. Additionally, the Samoans harbor almost 19% of their ancestry from mainland East Asia. Micronesian people have ~ 25% of their ancestry from various Papua New Guinea groups, mostly from New Guinea and New Ireland. They are also a little more than 1/4 mainland East Asian.

http://journals.plos.org/plosgenetics/article/figure/image?size=large&id=info:doi/10.1371/journal.pgen.0040019.g007

Populations that Melanesians are closest to outside of the Pacific region
Melanesians are genetically closest to those in East Asia, but are still very distant from them. Africans and Europeans are the most distant populations to Melanesians, genetically.

Populations that Polynesians are closest to genetically outside the Pacific

Polynesians are very weakly associated with Melanesians and Papuans genetically. They are genetically closer to both Taiwan Aboriginal populations and mainland East Asians. It is likely that their origins predominate in Taiwan. However, as mentioned earlier, there is a degree of Papuan ancestry in some Remote Oceanian groups.

Most Melanesians have no "Austronesian" ancestry, and none of the Papuan groups harbor Austronesian ancestry

Some, but not all Austronesian-speaking Melanesian populations contain a small amount of the "Austronesian" genetic signature in their genomes, while no Papuan-speaking groups in Near Oceania have any Austronesian ancestry. This shows that while there is some correlation between linguistics and genetics in Near Oceania, there is a very weak correlation. This also suggests that Austronesian-speaking groups in Melanesia were perhaps Papuan-speaking originally. Furthermore, it seems that the language shift occurred in these Austronesian-speaking populations without high rates of intermarriage.

Papuan New Guinea populations are extremely diverse genetically, forming up to 7 different genetic clusters at K=10

When K runs were done on Melanesian, Austronesian, and European (French) populations, Near Oceanians were assigned to 7 different clusters. The island of New Britain alone was divided into 5 different genetic clusters. What is remarkable is that some populations in New Britain that share more cluster membership with those in New Ireland than they do with any population in New Britain. These three populations are the Tolai (Kabakada), Tolai (Vunairoto), and Mussau. Given Mussau's closer proximity to New Ireland than to New Britain, it makes sense that they are genetically closer to New Ireland populations than they are to New Britain populations. As for the Tolai, thy primarily reside in the Gazelle Peninsula of New Britain, which is just a coastline away from New Ireland, so their strong genetic affiliation with New Ireland populations also makes sense. The more inland and isolated populations in New Britain formed clusters of their own.

http://journals.plos.org/plosgenetics/article/figure/image?size=large&id=info:doi/10.1371/journal.pgen.0040019.g006

link to the study: http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.0040019

MonkeyDLuffy
06-13-2018, 04:12 PM
It's a very old paper, more than 10 years old, but I agree we need more studies on Early east eurasian groups, even AASI which was most likely related to these populations.