Résumé

The origins of the Malagasy raise questions about ancient connections between continents; moreover, because ancestors are fundamental to Malagasy society, Malagasy origins is also a heated topic around the country, with numerous proposed hypotheses. Our analyses provides a comprehensive view of genomic diversity (including maternal lineages, paternal lineages, and genome-wide data) based on a sampling of 257 villages across Madagascar. The observed spatial patterns lead to a scenario of a recent and sex-biased admixture between Bantu and Austronesian ancestors across the island. Moreover, we find geographical influences creating subtle signals of genetic structure that are independent of the Bantu/Austronesian admixture, suggesting that recent history has a role in the genomic diversity of the Malagasy. We identified a strong signal of biological adaptive selection that happened during the last millennium and impacted the entire country (some 25 million individuals). This illustrates how natural selection can impact the human genome; in particular, selection should not be seen only as a slow process acting over a large number of generations, but instead as a force which can sometimes act rapidly even during very recent human history.Also it suggest that when the two populations came into contact in Madagascar, fitness differences played a role in the history of the settlement of Madagascar even before the admixture. Biology can thus play a role in historical events and should be considered when discussing the settlement of a new environment such as Madagascar.

Référence

Denis Pierron, « Genomic landscape of human diversity across Madagascar », IAST Lunch Seminar, Toulouse : IAST, 27 novembre 2018, 12h45–13h45, salle MF 323.