Humans went out of Africa for shellfish

The lure of a seafood diet may explain why early humans came out of Africa, according to research by the universities of Leeds and Glasgow published in Science this week.

Early modern humans in East Africa survived on an inland diet based on big game but by 70,000 years ago their diet had changed to a coastal one consisting largely of shellfish. However, dramatic climate change seems likely to have reduced the Red Sea’s shellfish stocks. New DNA evidence suggests their taste for life beside the sea caused them to set off from Africa to find new, better fishing grounds.

The international project shows – contrary to previous thinking – that early modern humans spread across the Red Sea from the Horn of Africa, along the tropical coast of the Indian Ocean towards the Pacific, in just a few thousand years.

Leeds biologist Dr Martin Richards said: “What’s more, those early settlers were the ancestors of all non-Africans alive today – including modern Europeans, whose ancestors splintered off from the small group of pioneers somewhere around the Persian Gulf.”

Glasgow statistician Dr Vincent Macaulay: “Ultimately, we are trying to make models which can explain the patterns of genetic variation seen across different human populations. This is vital for developing efficient strategies to identify the genetic mutations behind many common diseases. But in the process we are learning quite a lot about prehistory. A current hot topic is just how modern humans dispersed from Africa. Our research strongly suggests that they took a route along the southern Asian coast less than 80,000 years ago, venturing north rather later.”

The team looked at DNA from aboriginal populations of South East Asia. It has long been recognised that the Orang Asli of the Malay Peninsula—who today number no more than tens of thousands—might hold a key to our past. They are directly descended from the first modern people to settle in South East Asia. Comparing their DNA with that of other people around the world allowed the team to piece together what happened in those formative years—helping to rewrite the human story.

’Single, rapid coastal settlement of Asia revealed by analysis of complete mitochondrial genomes’ by Macaulay et al is published in the 13 May edition of Science.