Austro-Asiatic Tribes of Northeast India Provide Hitherto Missing Genetic Link between South and Southeast Asia B. Mohan Reddy 1 *, B. T. Langstieh 1,2 , Vikrant Kumar 1,3 , T. Nagaraja 1 , A. N. S. Reddy 1 , Aruna Meka 1 , A. G. Reddy 4 , K. Thangaraj 4 , Lalji Singh 4 1 Biological Anthropology Unit, Indian Statistical Institute, Hyderabad, India, 2 Department of Anthropology, Northeast Hill University, Shillong, India, 3 Genome Institute of Singapore, Singapore, Singapore, 4 Centre for Cellular and Molecular Biology, Hyderabad, India Northeast India, the only region which currently forms a land bridge between the Indian subcontinent and Southeast Asia, has been proposed as an important corridor for the initial peopling of East Asia. Given that the Austro-Asiatic linguistic family is considered to be the oldest and spoken by certain tribes in India, Northeast India and entire Southeast Asia, we expect that populations of this family from Northeast India should provide the signatures of genetic link between Indian and Southeast Asian populations. In order to test this hypothesis, we analyzed mtDNA and Y-Chromosome SNP and STR data of the eight groups of the Austro-Asiatic Khasi from Northeast India and the neighboring Garo and compared with that of other relevant Asian populations. The results suggest that the Austro-Asiatic Khasi tribes of Northeast India represent a genetic continuity between the populations of South and Southeast Asia, thereby advocating that northeast India could have been a major corridor for the movement of populations from India to East/Southeast Asia. Citation: Reddy BM, Langstieh BT, Kumar V, Nagaraja T, Reddy ANS, et al (2007) Austro-Asiatic Tribes of Northeast India Provide Hitherto Missing Genetic Link between South and Southeast Asia. PLoS ONE 2(11): e1141. doi:10.1371/journal.pone.0001141 INTRODUCTION Two major routes have been proposed for the initial peopling of East Asia; one via Central Asia to Northeast Asia, which subsequently expanded towards Southeast Asia and beyond, and the other through India to Southeast Asia and further to different regions of East Asia [1]. It is pertinent in this context that the Indian subcontinent has been considered as a major corridor for the migration of human populations to East Asia [2–4]. Given its unique geographic position, Northeast India is the only region which currently forms a land bridge between the Indian subcontinent and Southeast Asia, hence hypothesized as an important passage for the initial peopling of East Asia. This region is inhabited by populations belonging to Indo-European, Tibeto-Burman and Austro-Asiatic linguistic families. Whereas Indo-European populations are also found in other parts of India, West Asia and Europe but absent in East Asia, Tibeto-Burman populations are otherwise found only in East Asia. However, Austro-Asiatic speakers, hypothesized as probably the earliest settlers in the Indian subcontinent ([5] and references their in), are also found in other parts of India as well as in East/Southeast Asia. Therefore, if Northeast India had served as an initial corridor, it is likely that the Austro-Asiatic tribes of this region should provide hitherto missing genetic link, which may reflect genetic continuity between Indian and East/Southeast Asian populations. Based on mitochondrial DNA (mtDNA) and Y-chromosome markers, Cordaux et al. [6] observed genetic discontinuity between the Indian and southeast Asian populations and inferred that Northeast India might have acted as a barrier rather than the facilitator of the movement of populations both into and out of India. However, this study included only a few Tibeto-Burman populations of Northeast India whose distribution is restricted only to this region in India [7–8], besides a few other populations from other parts of India, possibly with no genetic link with East Asians. It is therefore imperative that the framework of testing such a hypothesis should include adequate representation of these people from Northeast India. Further evidence is needed by way of determining the mtDNA and Y-chromosome haplogroups/ lineages of the Austro-Asiatic tribes of the northeastern region and their comparison with appropriate set of South and Southeast Asian populations. The Northeastern part of India is sandwiched by the marked presence of the young fold mountains of Eastern Himalayas on the northern side and the Indian Ocean on its southern side. The archaeological evidences, based on stone tools from the Garo hills of the Meghalaya region of Northeast India (Figure 1), suggest that this region might have been inhabited as early as in the Paleolithic period [9–12]. Within this Meghalaya region, one finds Khasi tribes whose language belongs to the Khasi-Khmic subfamily of the Austro-Asiatics [13], the other two branches of Austro-Asiatics being Mundari and Mon-Khmer, amidst the ethnic majority of Tibeto-Burman populations. Further, the Austro-Asiatic popula- tions of Meghalaya and one of the contiguous Tibeto-Burman tribes namely, Garo, practice matrilineal pattern of descent and matrilocal pattern of residence while the other populations of this region are patrilineal and patrilocal. Such extreme cultural and linguistic diversity of this region may also imply high degree of genetic heterogeneity possibly due to passage of diverse popula- tions through this region. Despite a possible major role played in the population dispersal by the Northeastern region, as transect between India and East Asia, the extent and nature of mtDNA and Y-chromosome diversity of this region is not adequately studied. Therefore, we present results based on the analyses of mtDNA and Y-Chromosome Single Nucleotide Polymorphisms (SNPs) and Short Tandem Repeats (STRs) data of the 8 subgroups of the Austro-Asiatic Khasi from Northeast India (Table 1 and Figure 1), probably for the first time, along with that of the other Academic Editor: Philip Awadalla, University of Montreal, Canada Received March 20, 2007; Accepted October 16, 2007; Published November 7, 2007 Copyright: ß 2007 Reddy et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This project was funded by Indian Statistical Institute. Competing Interests: The authors have declared that no competing interests exist. * To whom correspondence should be addressed. E-mail: bmr@isical.ac.in PLoS ONE | www.plosone.org 1 November 2007 | Issue 11 | e1141