Genome wide evidence of Austronesian-Bantu admixture and cultural reversion in a hunter-gatherer group of Madagascar

Linguistic and cultural evidence suggests that Madagascar was the final point of two major dispersals of Austronesian and Bantu speaking populations. Today, Mikea are described as the last known Malagasy population reported to be still practising a hunter-gatherer life-style. It is unclear, however, whether Mikea descend from a remnant population that existed before the arrival of Austronesian and Bantu agriculturalists or whether it is only their life-style that separates them from the other contemporary populations of South Madagascar. In order to address these questions we have performed a genome wide analysis of >700,000 SNP markers on 21 Mikea, 24 Vezo and 24 Temoro individuals together with 50 individuals from Bajo and Lebbo populations from Indonesia. Our analyses of these data in the context of data available from other Southeast Asian and African populations reveal that all three Malagasy populations are derived from the same admixture event involving Austronesian and Bantu sources. In contrast to the fact that most of the vocabulary of the Malagasy speakers is derived from the Barito group of the Austronesian language family we observe that only one third of their genetic ancestry is related to the populations of Java-Kalimantan-Sulawesi area. Because no additional ancestry components distinctive to for the Mikea were found, it is likely that they have adopted their hunter-gatherer way of life by through cultural reversion. 69 samples were analysed with the Illumina platform OmniExpress BeadChips and are described herein.

语言学与文化证据表明，马达加斯加是南岛语族（Austronesian）与班图语族（Bantu）人群两次大迁徙的最终落脚点。时至今日，米基亚人（Mikea）被认为是目前已知仍维持狩猎采集生活方式的最后一支马尔加什人群。但目前尚不明确的是，米基亚人究竟是南岛语族与班图语族农耕人群抵达马达加斯加之前就已存在的遗留种群后裔，还是仅仅因其生活方式与马达加斯加南部其他当代人群有所区别。为解答上述问题，本研究对21名米基亚人、24名韦佐人（Vezo）、24名特莫罗人（Temoro）以及印度尼西亚巴乔人（Bajo）和勒博人（Lebbo）的共50名个体的70余万个单核苷酸多态性（Single Nucleotide Polymorphism，SNP）标记开展了全基因组分析。结合东南亚与非洲其他人群的公开数据对本研究数据展开分析后发现，三支马尔加什人群均源自同一次由南岛语族与班图语族来源人群参与的遗传混合事件。与马尔加什语词汇大多源自南岛语族巴里托语群（Barito group）的现象不同，本研究发现马尔加什人群仅三分之一的遗传祖源与爪哇-加里曼丹-苏拉威西地区的人群相关。由于未发现米基亚人带有独特的额外祖源成分，推测其狩猎采集生活方式是通过文化逆转形成的。本研究采用因美纳（Illumina）OmniExpress基因分型芯片对69份样本进行了分析，相关细节已在本文中详述。