Demographic transitions and migration in prehistoric East/Southeast Asia through the lens of nonmetric dental traits

Abstract

The aim of this study is to examine and assess the nonmetric dental trait evidence for the population history of East and Southeast Asia and, more specifically, to test the two-layer hypothesis for the peopling of Southeast Asia. Using a battery of 21 nonmetric dental traits we examine 7,247 individuals representing 58 samples drawn from East and Southeast Asian populations inhabiting the region from the late Pleistocene, through the Neolithic, Bronze Age, Iron Age, and into the historic and modern periods. The chief data reduction technique is a neighbor-joining tree generated from the triangular matrix of mean measure of divergence values. Principal findings indicated a major dichotomization of the dataset into (1) an early Southeast Asian sample with close affinities to modern Australian and Melanesian populations and (2) a very distinct grouping of ancient and modern Northeast Asians. Distinct patterns of clinal variation among Neolithic and post-Neolithic Mainland Southeast Asian samples suggest a center to periphery spread of genes into the region from Northeast Asia. This pattern is consistent with archaeological and linguistic evidence for demic diffusion that accompanied agriculturally driven population expansion in the Neolithic. Later Metal Age affinities between Island and Mainland coastal populations with Northeast Asian series is likely a consequence of a South China Sea interaction sphere operating from at least 500 BCE, if not from the Neolithic. Such results provide extensive support for the two-layer hypothesis to account for the population history of the region.

Late Pleistocene hominin teeth from Laoya Cave, southern China

“…Turner, 1987;Matsumura and Oxenham, 2014). However, a suite of M 3 characteristics has been identified as taxonomically and phylogenetically informative, with varying reliability among different taxa (Olejniczak et al, 2008;Bailey et al, 2011;Martinón-Torres et al, 2012;Smith et al, 2012;Martínez de Pinillos et al, 2014;Gómez-Robles et al, 2015).…”

New Perspectives in Southeast Asian and Pacific Prehistory

“…Matsumura and Oxenham 2014) demonstrate an apparent genetic discontinuity between pre-and post-Neolithic populations. Events occurring during the Neolithic were apparently pivotal in terms of the micro-evolutionary history of Southeast Asia.…”

“…Note also that proponents of this hypothesis envisage the persistence of the Australo-Melanesian substratum till today amongst the populations of ISEA, albeit to varying degrees, rather than complete replacement by the immigrant Mongoloids. , Bellwood (1997: 92), Matsumura andHudson (2005), Hanihara (2006: 100), and Matsumura and Oxenham (2014), amongst others, have all advocated dual inheritance. Further, based on his study of the Gunung Sewu and other ISEA fossil skulls, Détroit (2002) proposed that ISEA has long been an 'inter-population hybridisation zone', with more complex population movements during the pre-Neolithic than the blanket term 'Australo-Melanesian' necessarily conveys.…”

Using Dental Metrical Analysis to Determine the Terminal Pleistocene and Holocene Population History of Java

“…For instance, the colonisation of Australia and Melanesia would have occurred via Sundaland, undertaken by colonists with Australo-Melanesian biological affinities. And according to the 'two-layer hypothesis', the populations across Southeast Asia retained these Australo-Melanesian affinities until approximately 4000 BP, when there was a southward expansion of Mongoloid populations from the early agricultural heartlands of southern and central China (Matsumura and Oxenham 2014). Bellwood's (1997) hypothesised expansion of Austronesian-speaking Southern Mongoloids from Taiwan across ISEA after 4000 BP represents the component of the two-layer hypothesis relevant to Java's population history.…”

“…Note also that proponents of this hypothesis envisage the persistence of the Australo-Melanesian substratum till today amongst the populations of ISEA, albeit to varying degrees, rather than complete replacement by the immigrant Mongoloids. Jacob (1967), Bellwood (1997: 92), Hudson (2005), Hanihara (2006: 100), Matsumura et al (2011) and Matsumura and Oxenham (2014), amongst others, have all advocated dual inheritance. Further, based on his study of the Gunung Sewu and other ISEA fossil skulls, Détroit (2002) proposed that ISEA has long been an 'inter-population hybridisation zone', with more complex population movements during the pre-Neolithic than the blanket term 'Australo-Melanesian' necessarily conveys.…”