Scientists say humans could have left Africa up to 70,000 years earlier than had been thought Humans could have left Africa up to 70,000 years earlier than previously thought, according to research that sheds new light […]

Humans could have left Africa up to 70,000 years earlier than previously thought, according to research that sheds new light on the history of the continent’s climate.

Scientists at Aberystwyth University have published a 150,000-year climatic record from Ethiopia, which shows conditions would have allowed early modern humans to move from Africa to Asia.

Previous genetic evidence had suggested the “out of Africa” dispersal took place 60,000 years ago.

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Our view is that those conditions would have allowed humans not just to expand their population but also to spread out of Africa. Professor Henry Lamb

But the scientists at Aberystwyth used a 300ft sediment core drilled from the bed of Ethiopia’s Lake Tana to show the right conditions existed between 90,000 and 130,000 years ago.

Professor Henry Lamb, a specialist in the study of lake-sediment records in climatic change, who led the study, said: “Recent fossil discoveries show earlier human presence in Arabia, China, South East Asia and Australia, putting the date of 60,000 years very much in question.

”The emerging consensus is that there were probably several episodes of dispersal from Africa into Asia, from as early as 130,000 years ago.

“This new record from Ethiopia supports this view by showing that the climate of the time was strongly conductive to the increase and spread of humans from Africa.”

Lake Tana is close to the earliest known fossil sites of homo sapiens in eastern Africa and to likely dispersal routes via the Nile Valley or across the Red Sea.

The scientists from Aberystwyth say its core record of climate change is highly relevant to current debates about the timing of “out of Africa”.

Their findings, published in Scientific Reports, were made by doing a chemical analysis of the core and taking images of the structure of the sediments below the lake bed.

Favourable climate

The core has been dated using luminescence – a technique for identifying when a grain of sand was last exposed to sunlight.

Younger sediments were dated using radiocarbon to produce one of the longest and most complete terrestrial climate records for eastern Africa.

The record shows a long period of moist, resource-rich conditions – a favourable climate for humans to expand beyond Africa – from about 130,000 to 90,000 years ago.

Since then, predominantly arid conditions in the region probably restricted human populations to a few moist refuges in the Ethiopian mountains.

Professor Lamb said: “The evidence from this core shows that between about 130,000 years ago and 90,000 years ago, the north east Africa was moist and highly environmentally favourable for the expansion of the population.

”Our view is that those conditions would have allowed humans not just to expand their population but also to spread out of Africa.

“This is highly relevant to the current debate about when and why humans left Africa.”