People from Africa and from the islands of southeast Asia made their first genetic contact with each other as early as the eighth century ad, on islands in the Indian Ocean.
Starting around 1,000 years ago, residents of East Africa, the Middle East, South Asia and the islands of southeast Asia formed a vast trading network. To survey this network’s genetic legacy, a team led by Nicolas Brucato and Francois-Xavier Ricaut at the University of Toulouse in France generated genomic data from two groups of people: individuals from the Comoros Islands — an archipelago in the Indian Ocean, about 300 kilometres east of the African mainland — and those in Kenya, which borders the Indian Ocean.
Comoros islanders and residents of Kenyan coastal communities bore traces of Middle Eastern ancestry dating to the period after the trade network emerged, the team found. Island residents were also related to inhabitants of Borneo, as a result of mixing as early as the eighth century ad.