The island in East Africa was one of the last great human conquests. A genetic study is now shedding new light on the mysterious settlement history of Madagascar. Accordingly, for a long time there was probably only a very small population of Asian origin, until a small group of African people joined them about 1000 years ago. This was followed by strong population growth, which had a strong impact on the nature and fauna of the island: the scientists say there is a connection between this population development and the loss of the island's large animal species.
Madagascar is considered particularly puzzling by anthropologists: Although this island is relatively close to the coast of East Africa, humans only spread to it very late. According to archaeological evidence, smaller groups of people may have lived in Madagascar earlier, but clearer traces only come from around 2000 years ago. What is particularly surprising is that today's inhabitants of the island, despite their proximity to East Africa, speak a language that is clearly influenced by Asia. Linguistic, genetic, and archaeological evidence now shows that today's population can be largely traced back to two groups: an Austronesian-speaking from Asia and a Bantu-speaking from Africa. What exactly happened, however, remains unclear.
A questioning look at population history and megafauna
In addition to further research into the settlement history, the study by the international team led by Alva Omar from the University of Toulouse also focused on the possible link with the loss of wildlife on the island. Although Madagascar is still considered a place of unique biological diversity, it was once richer by large species: In the last millennia, all animals weighing more than ten kilograms have disappeared - including outstanding species such as giant lemurs, turtles, special hippos and the gigantic elephant birds. Climatic changes, but also the influence of humans are already associated with it. But even with this development, the processes appear unclear.
To learn more about the history of the Malagasy people, the scientists evaluated genetic data collected as part of the "Madagascar Genetic and Ethnolinguistic" project. Her focus was on certain segments of the human chromosomes that can allow conclusions to be drawn about the origins and development processes in human history. The results were also linked to local ancestry information, and the researchers also ran computer simulations to shed light on what processes the genetic clues might be based on.
Population growth after interbreeding
As the researchers report, the results confirmed that the history of the Malagasy is largely due to the mixture of an Asian and an African group, with the Asian forming the more original. In detail, certain traces in the genome now suggest that the Asian indigenous population of Madagascar lived in isolation for more than 1000 years. According to the genetic traces, it must have been a surprisingly small group: the team suspects only a few hundred individuals.
But about 1000 years ago, a momentous development took place, as can be seen from the genetic evidence: Apparently a small group of Bantu-speaking Africans had come to Madagascar and mixed with the locals. After that, the population grew rapidly, as can be seen from the genetic material. Why remains unclear. Technology transfer may have played a role, but also the transmission of resistance to diseases. “The demographic spread of people has been accompanied by a cultural and ecological change on the island. Around the same time, settlements emerged in Madagascar,” says senior author Denis Pierron from the University of Toulouse.
According to the researchers, the findings now also shed more light on the disappearance of the large animal species: they probably fell victim to ecological changes on the island and to re-enactments, which apparently only began to increase 1000 years ago. "Our study supports the theory that the disappearance of megafauna was not directly caused by the arrival of humans on the island, but rather by a lifestyle change leading to both an expansion in human population and a decline in biodiversity Madagascar led,” said Pierron.
Perhaps further research can now clarify how, where and why the indigenous Asian population has remained isolated and small for so long and what the main factor in the developmental spurt after mixing with the Africans could have been, the scientists say.
Source: Cell Press, Article: Current Biology, doi: 10.1016/j.cub.2022.09.060