Climate change and human migration out of Africa
An international team of scientists have shown how climate change could have enabled the migration of Homo sapiens around 60 000 years ago.23/06/2021 By BGS Press
An international team of scientists, including Dr Jonathan Dean (now at the University of Hull) and Prof Melanie Leng (BGS Chief Scientist, environmental change, adaptation and resilience), have reconstructed how climate has changed over the last 200 000 years in eastern Africa. They have shown how climate change could have enabled the out of Africa migration of Homo sapiens around 60 000 years ago. The paper was published in Nature Communications, Earth & Environment in June 2021.
Homo sapiens is thought to have evolved in eastern Africa sometime before 200 000 years ago. We used geochemistry to examine hundreds of metres of sediment cores taken from the bed of a lake called Chew Bahir, in southern Ethiopia, and were able to work out how the climate changed going back through time.
We found that, from 200 000 to 125 000 years ago, the climate of eastern Africa was relatively wet, with at least 20 to 30 per cent more precipitation than the region receives today, meaning conditions were favourable for early humans with plenty of food and water available. Further studies have also shown wet conditions in other parts of Africa at this time. Under such conditions, humans could move relatively easily through Africa and some even ventured out of Africa to reach the Arabian peninsula, which they did well before 100 000 years ago. However, it does appear that these intrepid humans died out before they could disperse further.
From 125 000 years ago, the climate gradually became drier in eastern Africa. This long-term drying trend was interrupted by short-lived climate shifts that lasted a few thousand years. These have been linked to changes in the circulation of the north Atlantic Ocean, showing how changes in one part of the world can impact upon the climate in another.
One of these short-lived climate shifts was a wet period that occurred 62 000 to 60 000 years ago. This roughly coincides with the occurrence of the ‘successful’ out of Africa migration of Homo sapiens — the one that went on to populate the rest of the world. This wet period would have made the out of Africa migration possible by providing sufficient food and water resources for the humans to survive the long journey.
Over the past 60 000 years, the conditions have became increasingly challenging for the humans who stayed in eastern Africa. There were some particularly dry intervals where Chew Bahir completely dried out. At these times, humans had to seek refuge at higher elevations in Ethiopia, where they could still access sufficient food and water.
About the author
BGS has a long history of assisting relief efforts by providing satellite maps, data and interpretation to those affected by disasters, helping to identify hazardous areas to avoid.
Alessandro Novellino explains the importance of Earth Observation (EO) to help facilitate successful emergency responses after natural hazard occurrences.
Understanding the geology and natural resources of lithium will be vital as demand is forecast to significantly increase.
Dick Merriman is a former BGS Geologist, who retired from service in 2004. In 1971 he was chosen as part of a team to land on Rockall, a small, uninhabited islet and Site of Special Scientific Interest (SSSI). Today, on the 50th anniversary of the expedition, Dick recounts his experience.
The most intensively cultivated areas of South Asia are crucial for regional food security and have become global hotspots of groundwater exploitation.
The UK Geoenergy Observatory will allow scientists to better understand the processes and impacts of using warm water underneath UK cities as a sustainable heat source
Discover how BGS is working alongside partners to investigate the effectiveness of natural flood management initiatives and mitigate the threat of flooding.
Meet the team behind our geohazard products and datasets.