Polynesian mtDNA in extinct Native American population

The evidence seems to accumulate in favor of some Polynesian impact in South America:

Vanessa Faria Gonçalves et al., Identification of Polynesian mtDNA haplogroups in remains of Botocudo Amerindians from Brazil. PNAS 2013. Pay per view (six months embargo) → LINK [doi:10.1073/pnas.1217905110 ]

Abstract

There is a consensus that modern
humans arrived in the Americas 15,000–20,000 y ago during the Late
Pleistocene, most probably
from northeast Asia through Beringia.
However, there is still debate about the time of entry and number of
migratory waves,
including apparent inconsistencies between
genetic and morphological data on Paleoamericans. Here we report the
identification
of mitochondrial sequences belonging to
haplogroups characteristic of Polynesians in DNA extracted from ancient
skulls of
the now extinct Botocudo Indians from
Brazil. The identification of these two Polynesian haplogroups was
confirmed in independent
replications in Brazil and Denmark,
ensuring reliability of the data. Parallel analysis of 12 other Botocudo
individuals yielded
only the well-known Amerindian mtDNA
haplogroup C1. Potential scenarios to try to help understand these
results are presented
and discussed. The findings of this study
may be relevant for the understanding of the pre-Columbian and/or
post-Columbian
peopling of the Americas.

 

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.

See also in this blog: The genetic and phenotype complexity of the Oceanic language area.

 

Ancient Maori mtDNA

Terry points me to this paper:

Michael Knapp et al., Complete mitochondrial DNA genome sequences from the first New Zealanders. PNAS 2012. Open access ··> LINK [doi:10.1073/pnas.1209896109 ]

Abstract


The dispersal of modern humans across the globe began ∼65,000 y ago when people first left Africa and culminated with the settlement of East Polynesia, which occurred in the last 1,000 y. With the arrival of Polynesian canoes only 750 y ago, Aotearoa/New Zealand became the last major landmass to be permanently settled by humans. We present here complete mitochondrial genome sequences of the likely founding population of Aotearoa/New Zealand recovered from the archaeological site of Wairau Bar. These data represent complete mitochondrial genome sequences from ancient Polynesian voyagers and provide insights into the genetic diversity of human populations in the Pacific at the time of the settlement of East Polynesia.

The authors sequenced ancient mtDNA from the pre-colonial period from a museum material being returned for proper reburial. The remains belong to a population from Wairau Bar from the 13th-14th centuries, which were looted by British museums in the mid 20th century. 

Of the 19 individuals researched, only four provided valid sequences. All four Three were within the so-called Polynesian motif or haplogroup B4a1a1a, the other was Q1, a lineage of Melanesian origin also found, albeit rarely, among other Polynesians. All modern studied Maoris are B4a1a1a but Q1 is known to exist among Cook Islanders, for example. (Corrected: Q1 is mentioned but in the context of other Polynesian populations, not New Zealand).

Interestingly the authors also explain that the colonization of Eastern Polynesia was performed not in a series of small randomized migrations but in a single expansive wave in the 12th-13th centuries CE, what explains the relative homogeneity of their customs and languages. 

A recent reevaluation of the dates for the colonization of East Polynesia suggests that, contrary to earlier studies positing a relatively long (2,000 y) chronology for the region, the settlement of most of East Polynesia occurred rapidly, in the period from A.D. ∼1190–1290 (22). The authors determined that the expansion event occurred from the Society Islands, which were only settled 70–265 y previously. This rapid and recent expansion event, they argue, explains the “remarkable uniformity of East Polynesian culture, human biology and language” (22).

The cited reference (22) is:

Wilmshurst JM, Hunt TL, Lipo CP, Anderson AJ (2011) High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia. Proc Natl Acad Sci USA 108(5):1815–1820.