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Early humans may have left Africa and spread all over the globe because their home climate was drying up.
The idea comes from samples of marine sediment taken from northeastern Africa that show the area was cold and dry around 60,000 years ago, which is around the time humans might have migrated off that continent and into Europe and Asia. A team of scientists wrote in the journal Geology that after warm and wet conditions between 120,000 and 90,000 years ago, a period referred to as “Green Sahara,” enabled these prehistoric Homo sapiens to spread throughout Africa and into western Asia, there was a more arid period around 65,000 and 55,000 years ago that coincided with a popular timeline for a larger scale migration into Eurasia.
Study - Climate - Conditions - Impact - Migration
According to the study, those different climate conditions and their impact on human migration show “that both ‘push’ and ‘pull’ factors may have prompted Homo sapiens to colonize Eurasia.”
“The factors that drove our species ‘out of Africa’ remain a topic of vigorous debate,” the authors wrote. “Existing research invokes climate change as either providing opportunities or imposing limits on human migration.”
Sediment - Samples - Difference - Climate - Horn
The ocean sediment samples that show the difference in climate in the Horn of Africa came from the western side of the Gulf of Aden, the body of water between Somalia and Yemen that connects the Red Sea to the Arabian Sea.
Different layers of sediment in core samples represent different periods of time, because of how sediment accumulates, and hold evidence of climate conditions like temperature and rainfall. According to the University of Arizona, every 4 inches of sediment represented about 1,600 years.
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