Ancient remains of Asian species like rice and mung beans from excavated sites in Madagascar point to the first archaeological evidence that settlers from Southeast Asia might have colonised the island a thousand years ago, says a study.
The findings help solve one of the enduring mysteries of the ancient world -- why the inhabitants of Madagascar speak Malagasy, a language otherwise unique to Southeast Asia and the Pacific -- a region located at least 6,000 km away, the researchers said.
"Southeast Asians clearly brought crops from their homeland and grew and subsisted on them when they reached Africa," said Senior Author Nicole Boivin from School of Archaeology at University of Oxford.
The findings were published in the journal Proceedings of the National Academy of Sciences.
Genetic research has confirmed that the inhabitants of Madagascar do indeed share close ancestry with Malaysians, Polynesians, and other speakers of what is classed the Austronesian language family.
Until now, however, archaeological evidence of the Austronesian colonisation has been missing.
The international research team was able to identify the species of nearly 2,500 ancient plant remains obtained from their excavations at 18 ancient settlement sites in Madagascar, on neighbouring islands and on the eastern African coast.
They examined residues obtained from sediments in the archaeological layers, using a system of sieves and water.
They looked at whether the earliest crops grown on the sites were African crops or were crops introduced to Africa from elsewhere.
They found both types, but noted a distinct pattern, with African crops primarily concentrated on the mainland and the islands closest to the mainland.
In Madagascar, in contrast, early subsistence focused on Asian crops. The data suggested an introduction of these crops, both to Madagascar and the neighbouring Comoros Islands, by the eighth and 10th century.
"There are a lot of things we still don't understand about Madagascar's past; it remains one of our big enigmas. But what is exciting is that we finally have a way of providing a window into the island's highly mysterious Southeast Asian settlement and distinguishing it from settlements by mainland Africans that we know also happened," Boivin noted.
The analyses also suggest that Southeast Asians colonised not only Madagascar but also the nearby islands of the Comoros, because again the crops that grew there were dominated by the same Asian species.
By contrast, crops identified on the eastern African coast and near coastal islands like Mafia and Zanzibar were mainly African species like sorghum, pearl millet and baobab.
"This took us by surprise. After all, people in the Comoros speak African languages and they don't look like they have Southeast Asian ancestry in the way that populations on Madagascar do," study Lead Author Alison Crowther from University of Queensland, Australia, said.
"What was amazing to us was the stark contrast that emerged between the crops on the Eastern African coast and the offshore islands versus those on Madagascar, but also the Comoros," Crowther noted.