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

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. Overall design: 69 samples were analysed with the Illumina platform OmniExpress BeadChips and are described herein.

语言学与文化证据表明，马达加斯加是两次大规模南岛语系（Austronesian）与班图语系（Bantu）人群迁徙的最终落脚地。现今，米克阿人（Mikea）被认为是已知唯一仍保留狩猎采集生活方式的马尔加什（Malagasy）族群。但目前尚无定论：米克阿人究竟是南岛语系与班图语系农耕人群抵达马达加斯加之前便存在的遗留族群后裔，还是仅因生活方式与马达加斯加南部其他当代族群有所区分。为解答上述疑问，本研究对21名米克阿人、24名韦佐人、24名特莫罗人，以及来自印度尼西亚的巴乔（Bajo）与莱博（Lebbo）族群共50名个体的逾70万个单核苷酸多态性（Single Nucleotide Polymorphism, SNP）标记开展了全基因组分析。结合其他东南亚与非洲人群的公开数据对本研究数据集进行分析后，结果显示三支马尔加什族群均源自同一场涉及南岛语系与班图语系人群的遗传融合事件。尽管马尔加什语的绝大多数词汇源自南岛语系的巴里托（Barito）语族，但本研究仅发现其三分之一的遗传祖源与爪哇-加里曼丹-苏拉威西地区人群相关。由于未检测到米克阿人携带独特的祖源成分，推测其通过文化回归形成了当前的狩猎采集生活方式。实验设计：本研究共纳入69份样本，采用Illumina OmniExpress基因分型芯片（Illumina OmniExpress BeadChips）进行基因分型，相关细节已在本文中详述。