Evidence of Austronesian Genetic Lineages in East Africa and South Arabia: Complex Dispersal from Madagascar and Southeast Asia - PubMed (original) (raw)

. 2019 Mar 1;11(3):748-758.

doi: 10.1093/gbe/evz028.

Veronica Fernandes 2 3, Pradiptajati Kusuma 4, Viktor Černý 5, Connie J Mulligan 6, Pedro Soares 3 7, Teresa Rito 3 8 9, Céline Besse 10, Anne Boland 10, Jean-Francois Deleuze 10, Murray P Cox 11, Herawati Sudoyo 4 12, Mark Stoneking 13, Luisa Pereira 2 3, François-Xavier Ricaut 1

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Evidence of Austronesian Genetic Lineages in East Africa and South Arabia: Complex Dispersal from Madagascar and Southeast Asia

Nicolas Brucato et al. Genome Biol Evol. 2019.

Abstract

The Austronesian dispersal across the Indonesian Ocean to Madagascar and the Comoros has been well documented, but in an unexplained anomaly, few to no traces have been found of the Austronesian expansion in East Africa or the Arabian Peninsula. To revisit this peculiarity, we surveyed the Western Indian Ocean rim populations to identify potential Austronesian genetic ancestry. We generated full mitochondrial DNA genomes and genome-wide genotyping data for these individuals and compared them with the Banjar, the Indonesian source population of the westward Austronesian dispersal. We find strong support for Asian genetic contributions to maternal lineages and autosomal variation in modern day Somalia and Yemen. Surprisingly, this input reveals two apparently different geographic origins and timings of admixture for the Austronesian contact; one at a very early phase (likely associated with the early Austronesian dispersals), and a later movement dating to the end of nineteenth century. These Austronesian gene flows come, respectively, from Madagascar and directly from an unidentified location in Island Southeast Asia. This result reveals a far more complex dynamic of Austronesian dispersals through the Western Indian Ocean than has previously been understood and suggests that Austronesian movements within the Indian Ocean may have been part of a lengthy process, probably continuing well into the modern era.

Keywords: Austronesian; Madagascar; Polynesian motif; genome-wide data; mitochondrial DNA.

© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

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Figures

<sc>Fig</sc>. 1.

Fig. 1.

—Schematic representations of the B4a1a1 phylogeny based on complete mtDNA sequences. Subclades are represented by triangles. Subclades are colored according to their geographic origin, as shown on the map. (A) B4a1a1 tree. (B) B4a1a1b tree. (C) Geographic distribution of the subclades. KA, thousand years ago.

<sc>Fig</sc>. 2.

Fig. 2.

—ADMIXTURE analysis (K = 26) for 15 population groups and the two Yemeni and one Somali individuals carrying the Malagasy motif B4a1a1b maternal lineage. Each colored line represents a sampled population whose genetic background can be decomposed into 26 genetic components.

<sc>Fig</sc>. 3.

Fig. 3.

—Decay curves showing expected autosomal Asian ancestry at each generation of intermarriage to partners with no Asian ancestry. Decay rates for individuals with Indonesian (green) and Malagasy (blue) origins. Horizontal lines mark observed Asian ancestry for the Somali and Yemeni populations (orange), Indonesian descendant Yemeni 270 (green), and Malagasy descendants Somali 25 and Yemeni 115 (blue).

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