Search

Only 400 km off the coast of East Africa, the island of Madagascar is one of the last large land masses to have been colonized by humans. While many questions surround the human occupation of Madagascar, recent studies raise the question of human impact on endemic biodiversity and landscape transformation. Previous genetic and linguistic analyses have shown that the Malagasy population has emerged from an admixture that happened during the last millennium, between Bantu-speaking African populations and Austronesian-speaking Asian populations. By studying the sharing of chromosome segments between individuals (IBD determination), local ancestry information, and simulated genetic data, we inferred that the Malagasy ancestral Asian population was isolated for more than 1,000 years with an effective size of just a few hundred individuals. This isolation ended around 1,000 years before present (BP) by admixture with a small African population. Around the admixture time, there was a rapid demographic expansion due to intrinsic population growth of the newly admixed population, which coincides with extensive changes in Madagascar's landscape and the extinction of all endemic large-bodied vertebrates. Therefore, our approach can provide new insights into past human demography and associated impacts on ecosystems. An Asian population of few hundred individuals was isolated for more than 1,000 years This isolation ended around 1,000 years ago by admixture with a small African population The newly admixed Malagasy population underwent a rapid demographic expansion The population growth coincides with extensive changes in Madagascar's landscape Based on genomic studies, Alva et al. show that the Malagasy ancestral Asian population was isolated for more than 1,000 years. This isolation ended around 1,000 years BP by admixture with a small African population. Around this time, there was a rapid demographic expansion growth, which coincides with extensive changes in Madagascar's landscape. [ABSTRACT FROM AUTHOR]