A new study conducted by geoscientists from the University of Arizona shows that human beings migrated from Africa more than 60,000 years ago due to a major climate change, putting to rest questions about the kind of influence that climate change had on the first inhabitants of the African continent.
The report, titled “A Climatic Context for the Out-of-Africa Migration”, proves that weather patterns in the Horn of Africa underwent a major shift from wet to extremely dry about 70,000 years ago.
According to Jessica Tierney, a UA associate professor of geosciences at the University of Arizona, the research team has acquired critical data that proves that when most human species left Africa, it was extremely dry in northeast Africa.
“Our data say the migration comes after a big environmental change. Perhaps people left because the environment was deteriorating. There was a big shift to dry and that could have been a motivating force for migration,” Tierney said in a press release.
Tracing Back the Weather Patterns
Led by Tierney, the team of geoscientists was able to successfully trace back the climatic situation in the Horn of Africa about 200,000 years ago. They did so by analyzing essential ocean deposits obtained from the western part of the Gulf of Aden.
Using the same methodology, the team reconstructed the region’s climate back to about 70,000 years ago when Homo erectus moved out of Africa. In order to find the right core of ocean sediments, the team enlisted curators from the Lamont-Doherty Core Repository.
The curators provided a core obtained from the Horn of Africa in 1965, whose sediments date back to more than 200,000 years ago.
To decipher the region’s temperature record, the researchers tested the core’s sediment layers for alkenones, special chemicals made of aquatic algae, whose composition changes with the ocean temperatures.
The team also studied the ancient leaf wax on the core, whose chemical composition also changes with ocean temperatures. This analysis provided critical data on the ancient rainfall fluctuations in the region.
The study, which was funded by the National Science Foundation and the David and Lucie Packard Foundation, has also revealed essential facts about the climate of northeast Africa at the time of human migration from Africa.
From this data, the researchers concluded that a major climatic transition in Africa from a “Green Sahara” to a dry phase forced the early man to leave the continent.
by Fredrick Ngugi
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