Climate Change and Postglacial Human Dispersals in Southeast Asia

Abstract

Modern humans have been living in Island Southeast Asia (ISEA) for at least 50,000 years. Largely because of the influence of linguistic studies, however, which have a shallow time depth, the attention of archaeologists and geneticists has usually been focused on the last 6,000 years--in particular, on a proposed Neolithic dispersal from China and Taiwan. Here we use complete mitochondrial DNA (mtDNA) genome sequencing to spotlight some earlier processes that clearly had a major role in the demographic history of the region but have hitherto been unrecognized. We show that haplogroup E, an important component of mtDNA diversity in the region, evolved in situ over the last 35,000 years and expanded dramatically throughout ISEA around the beginning of the Holocene, at the time when the ancient continent of Sundaland was being broken up into the present-day archipelago by rising sea levels. It reached Taiwan and Near Oceania more recently, within the last approximately 8,000 years. This suggests that global warming and sea-level rises at the end of the Ice Age, 15,000-7,000 years ago, were the main forces shaping modern human diversity in the region.

GenGIS: A geospatial information system for genomic data

“…The tree of E1 sequences was rooted by including five sequences from the sister haplogroup E2 in the parsimony analysis. Given the rooting induced by the E2 sequences, the earliest split in the E1 tree separates a single individual in Palu, Sulawesi, from the rest of the E2 sequences; this is consistent (albeit weakly) with the hypothesis of Soares et al (2008), that northeastern Sunda (i.e., eastern Borneo) or western Sulawesi served as the originating point for subclades of haplogroup E. All of the sequences from northern Borneo, the Philippines, and Taiwan constitute a clade in the tree of E1 sequences, which is also consistent with the spread of ancestral E1 sequences north from Sunda (roughly, western Indonesia), but there is considerable intermingling within the northern and southern groups (Supplemental Fig. 7).…”

“…A phylogenetic analysis of the entire set would not be informative, because many of the observed haplogroups have migrated in and out of the region in the last 50,000 yr and because lineages that appear in one location will subsequently be spread to others. Haplogroup E is largely restricted to ISEA and appears to have arisen ;25,000-35,000 yr ago Soares et al 2008). The subsequent divergence of this haplogroup into subclades E1a, E1b, E2a, and E2b covers a period from ;17,000 to ;4500 yr ago and may track important migrations that followed the last glacial maximum of 19,000 yr ago (Soares et al 2008).…”

“…Haplogroup E is largely restricted to ISEA and appears to have arisen ;25,000-35,000 yr ago Soares et al 2008). The subsequent divergence of this haplogroup into subclades E1a, E1b, E2a, and E2b covers a period from ;17,000 to ;4500 yr ago and may track important migrations that followed the last glacial maximum of 19,000 yr ago (Soares et al 2008). Of particular importance is the potential influence of Wallace's Line (Mayr 1944), which splits Indonesia into a region (Sundaland) that was contiguous with the Asian mainland during the last glaciations, and a set of islands (collectively ''Wallacea,'' which includes Sulawesi and Lombok) that were not.…”

“…To approximate the hypothesis of Soares et al (2008), we created a set of four geographic polylines that radiate out from Borneo in different directions: one toward Sulawesi, one heading north to Taiwan, and two spreading southeast or southwest away from Wallace's Line. The dashed lines in Figure 3 indicate the manually drawn polylines that correspond to these four migration paths: in each case, we used Borneo as a starting point for the polyline, and extended the line to locations in the appropriate direction that were progressively more distant from the starting location.…”

Human genetics of the Kula Ring: Y-chromosome and mitochondrial DNA variation in the Massim of Papua New Guinea

“…Haplogroups F1a, B4-16261*(xB4a1a1a) and B4a1a1a (also known as the 'Polynesian motif') are of (ultimate) AS origin, 51,52 although B4a1a1a may also have originated in descendants of East Asians residing in Nusa Tenggara [53][54][55] or in the Bismarck Archipelago. 8 Haplogroups E*(xE2) and E2 are likely of Taiwanese/Island Southeast AS origin 56 (here also classified as AS), whereas haplogroups P*(xP1), P1, Q1 and Q2 have a NO origin. 57 Like the NRY haplogroups, also the mtDNA haplogroups were not homogeneously distributed throughout the Massim (Figure 2b).…”