Patterns of prehistoric human mobility in Polynesia indicated by mtDNA from the Pacific rat

Abstract

Human settlement of Polynesia was a major event in world prehistory. Despite the vastness of the distances covered, research suggests that prehistoric Polynesian populations maintained spheres of continuing interaction for at least some period of time in some regions. A low level of genetic variation in ancestral Polynesian populations, genetic admixture (both prehistoric and post-European contact), and severe population crashes resulting from introduction of European diseases make it difficult to trace prehistoric human mobility in the region by using only human genetic and morphological markers. We focus instead on an animal that accompanied the ancestral Polynesians on their voyages. DNA phylogenies derived from mitochondrial control-region sequences of Pacific rats (Rattus exulans) from east Polynesia are presented. A range of specific hypotheses regarding the degree of interaction within Polynesia are tested. These include the issues of multiple contacts between central east Polynesia and the geographically distinct archipelagos of New Zealand and Hawaii. Results are inconsistent with models of Pacific settlement involving substantial isolation after colonization and confirm the value of genetic studies on commensal species for elucidating the history of human settlement.

Origins and dispersals of Pacific peoples: Evidence from mtDNA phylogenies of the Pacific rat

“…Fresh tissues were extracted as described (9). We amplified and sequenced Ϸ240 base pairs of the hypervariable mitochondrial control region; see Supporting Text, which is published as supporting information on the PNAS web site, for specific methods.…”

“…Previous research focused on mtDNA variation within East Polynesian populations of R. exulans (9) and showed that this rat was an excellent proxy for tracing the movement of prehistoric Polynesian peoples. Our analyses identified interaction spheres and specific population origins within Polynesia.…”

Recent Southeast Asian domestication and Lapita dispersal of sacred male pseudohermaphroditic “tuskers” and hairless pigs of Vanuatu

“…This process of cultural assimilation and absorption has likely characterized much of coastal Southeast Asia (9), obscuring the previously more widespread distribution of human mtDNA Haplogroup B that may have existed 3,500 years ago. Thus, the analyses of pig and wild boar diversity may provide information not available from examining only human variation as has been shown for analyses of the Pacific rat (14)(15)(16). Additional sampling of Southeast Asian wild boar diversity is required to further refine the site of domestication of the PC of pigs and potentially the proximate origin of the Lapita cultural complex (Fig.…”

“…On smaller islands of Micronesia and Polynesia in particular the pig disappeared from the archaeological record before European contact, presumably because of its adverse competition with humans for land resources (12,13). The Pacific rat, Rattus exulans, is thus the most widespread of the introduced animals of the Pacific and as such has been used effectively as a proxy for human settlement and exchange (14)(15)(16). Unlike the European introduced rats of distinct species that could not interbreed with the Pacific rat, studies of Pacific pigs, dogs, and chickens are complicated by the introduction of conspecifics within the last few hundred years.…”

Distinguishing human ethnic groups by means of sequences from Helicobacter pylori : Lessons from Ladakh

“…Alternative approaches have focused on commensals and parasites that accompany human migrations, including viruses such as JC virus (20,21) and human T-lymphotrophic virus (22), fungi (23), rats (24), and the bacterium Helicobacter pylori (25)(26)(27). In the present study, we investigated the usefulness of H. pylori, a Gram-negative bacterium that persistently colonizes the stomach of Ͼ50% of humans, as a potential genetic marker for deciphering recent human migrations.…”