November 13, 2012

Hawaiian origins (Kim et al. 2012)

PLoS ONE 7(11): e47881. doi:10.1371/journal.pone.0047881

Population Genetic Structure and Origins of Native Hawaiians in the Multiethnic Cohort Study

Sung K. Kim et al.

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.

Link

10 comments:

MOCKBA said...

The one surprising part here is the origin of the SNP data: a WGA study of breast cancer. Apparently people hope that in populations with strong founder effects, WGA may net them something, what one may never see in a larger, homogenous population?

Of course it probably also means that we will not be able to see the raw data?

terryt said...

"the ancestral origins of Polynesians remain in question".

That's a bit of an exaggeration. Especially when later:

"A significant proportion of Melanesian ancestry (mean = 32%) was estimated in 100% self-reported Native Hawaiians"

Didn't we already know that?

"This notable proportion of Melanesian admixture supports the 'Slow-Boat' model of migration of ancestral Polynesian populations from East Asia to the Pacific Islands".

Not particularly 'slow'. This paper is relevant (courtesy of Maju):

http://www.sciencedirect.com/science/article/pii/S0305440309004646

The dates for Lapita/Austronesian expansion through the Pacific:

Lapita origin in the Bismark Archipelago: 3450-3350 BP
Lapita/Austronesian to Reefs-Santa Cruz: 3200 BP
Lapita/Austronesian to Vanuatu, New Caledonia, Fiji, Tonga and Samoa: 3200-2800 BP.

So that makes the Austronesian/Polynesian movement through Near Oceania as quite rapid. No more than 650 years from leaving the admiralty Islands to reaching Samoa, and possible less than 650 years. The greater Melanesian genetic contribution in islands west of Fiji as against those to the east is usually accepted as being the product of later movement east from the Solomon Islands.

It was then another 1000 years before people ventured further east from Samoa to Hawaii, of course.

"In addition, approximately 1,300 years ago a single, strong expansion of the Native Hawaiian population was estimated"

And that is obviously associated with their arrival in Hawaii.

Thomas Dougherty said...

The authors themselves admit the biggest thing that really makes me skeptical: "...our current analyses cannot differentiate between long-range versus short range admixture events."

Unless they have some dating of the admixture, this doesn't tell us whether we're looking at a Slow Boat with admixture in Melanesia, or an Express Train with admixture in colonial Hawaii (or something else entirely). This is compounded by the fact that the include no other Polynesian samples.

terryt said...

"This is compounded by the fact that the include no other Polynesian samples".

My understanding is that Eastern Polynesians are pretty much all alike, while Western Polynesians (basically Tongans and Samoans) have an even higher level of Melanesian ancestry. This level basically increases as we move progressively west from Fiji to the Solomon islands.

MOCKBA said...

I've been struggling for years with a founder SNP uniquely common in Hawaiians. Of course its high frequency can attest to a bottleneck, which is possible to date by assessing other variation in the vicinity. But what's interesting is that the SNP, although generally found across the Astronesian paths over the Pacific, is rare or absent in Samoa,Fiji, and Indonesia. It's rare but detectable in Filipino population which must be close to the migration root.

But of course Melanesian data or specimens are just too hard to come by. Even my Fiji set, once you make a reasonable effort to remove possible Indo-Fijians, is getting far too thin.

terryt said...

"I've been struggling for years with a founder SNP uniquely common in Hawaiians".

What founder SNP are you talking about? Is it in mt-DNA B4a1a?

"But of course Melanesian data or specimens are just too hard to come by".

On the contrary, I think the data for Melanesia is quite good. Maju and I managed to collect a few references here:

http://forwhattheywereweare.blogspot.co.nz/2012/10/the-genetic-and-phenotype-complexity-of.html

MOCKBA said...

Thanks, Terryt! Nice review there. Of course I meant *autosomal* (rather than Y chr / mt) data, along the lines of the paper described in this blog entry...

terryt said...

"Of course I meant *autosomal*"

I did realise that, however haplogroup data is all we have yet. Dienekes methods for comparisons of autosomal data is very new and, as you remarked, we as yet have no data from the region for Dienekes to work with yet. but what is the 'founder SNP uniquely common in Hawaiians'?

Kalani said...

Can someone help explain why my paternal aunt who is Filipino, has a match with a half Tongan man at a low %? I understand the ancient connection, but this guy is a match to me because my mother is Hawaiian, but we're distant, and understandably so. Unlike Maoris who match me and my mother at very high %, the half Tongan guy I'd expect to have a less chance of matching to a hawaiian or maori, but to a Filipino?

terryt said...

"Unlike Maoris who match me and my mother at very high %, the half Tongan guy I'd expect to have a less chance of matching to a hawaiian or maori, but to a Filipino?"

A substantial proportion of Polynesian ancestry lies in the Philippines, which may be the explanantion. Tongans, Maoris and Hawai'ians are Polynesians of course, although Tongans (and Fijians) appear to have a later, further admixture of the original Melanesian element. You may be looking at the result of some later factors though.