Human Genes and Biocultural History in Southeast Asia

Abstract

Southeast Asians share some unifYing traits within their biocultural diversity. In this report I discuss the hypothesis that temporal and spatial aspects of this unity reflect human settlement in Southeast Asia from the Thai-Indochina area out through Indonesia, and on to Australia-New Guinea, starting perhaps 40,000 or more years ago. Several rare or regional genetic variants are distributed from the mainland eastward to Indonesia, or on to New Guinea. Several cultural traits also show an easterly trend, suggesting that Island and Mainland Southeast Asia are culturally related in terms of a preagricultural past. Faunal distributions suggest that most of Indonesia's extant land vertebrates arrived prehistorically from continental Southeast Asia across a landmass now under water on the Sunda Shelf. This range expansion of animals, and also of humans, through Island Southeast Asia may have been the result of the periodic expansion and contraction of exposed land on the Sunda Shelf, caused by Pleistocene glaciations at higher latitudes. Together, these genetic traits, cultural motifs, and biogeographical considerations support the scenario of a pre-Holocene human expansion from the Thai-Indochina area through Indonesia. In contrast, today's language affiliations in Southeast Asia do not conform well to an eastward trend; they may be the products of recent, Holocene events. KEYWORDS: Sundaland, rare genetic traits, cultural traits, faunal distributions.