Ancestry of the Iban Is Predominantly Southeast Asian: Genetic Evidence from Autosomal, Mitochondrial, and Y Chromosomes

Tatum S Simonson,Lynn B Jorde,Scott Woodward,Jinchuan Xing,Peter Loa,Chad D Huff,Yuhua Zhang,Robert Barrett,Bryan Mowry,David J Witherspoon,W Scott Watkins,Edward Jerah,Vincent Macaulay

doi:10.1371/journal.pone.0016338

Abstract

Humans reached present-day Island Southeast Asia (ISEA) in one of the first major human migrations out of Africa. Population movements in the millennia following this initial settlement are thought to have greatly influenced the genetic makeup of current inhabitants, yet the extent attributed to different events is not clear. Recent studies suggest that south-to-north gene flow largely influenced present-day patterns of genetic variation in Southeast Asian populations and that late Pleistocene and early Holocene migrations from Southeast Asia are responsible for a substantial proportion of ISEA ancestry. Archaeological and linguistic evidence suggests that the ancestors of present-day inhabitants came mainly from north-to-south migrations from Taiwan and throughout ISEA approximately 4,000 years ago. We report a large-scale genetic analysis of human variation in the Iban population from the Malaysian state of Sarawak in northwestern Borneo, located in the center of ISEA. Genome-wide single-nucleotide polymorphism (SNP) markers analyzed here suggest that the Iban exhibit greatest genetic similarity to Indonesian and mainland Southeast Asian populations. The most common non-recombining Y (NRY) and mitochondrial (mt) DNA haplogroups present in the Iban are associated with populations of Southeast Asia. We conclude that migrations from Southeast Asia made a large contribution to Iban ancestry, although evidence of potential gene flow from Taiwan is also seen in uniparentally inherited marker data.

Highlights

Many distinct ethnic groups reside within the Malaysian state of Sarawak, reflecting broader patterns of cultural and linguistic diversity observed throughout Island Southeast Asia (ISEA) [1]
Genome-wide autosomal variation To investigate the genetic structure of the Iban and other East and Southeast Asian populations, we combined overlapping single-nucleotide polymorphism (SNP) from three data sets
Pairwise-population FST values calculated between the Iban and each of the ten groups indicate that the Iban population is genetically most similar to Indonesian, Cambodian, and Thai population samples (Table 1; see Fig. S1 for admixture analysis)

Summary

Introduction

Many distinct ethnic groups reside within the Malaysian state of Sarawak, reflecting broader patterns of cultural and linguistic diversity observed throughout Island Southeast Asia (ISEA) [1]. The maternal and paternal genetic lineages present among inhabitants throughout Taiwan, East Asia, and ISEA have been independently studied using either non-recombining Y (NRY) or mitochondrial DNA (mtDNA) polymorphism data [10,18,19,20,21]. Recent studies of genome-wide SNP data [31] suggest a southern origin of East and Southeast Asian populations.

Results

Conclusion