Ancient humans left Africa to escape drying climate

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Humans may have been driven out of Africa 70,000 years ago by a changing climate, according to a new study. While scientists have long suspected the region may have experienced climatic changes in line with the known period of migration, a new study has found evidence to suggest the people may have been escaping a ‘deteriorating’ environment.

Researchers analyzing a core of ocean sediment have traced the climate in northeast Africa back 200,000 years, revealing the region dried out and became cooler following a ‘Green Sahara’ wet phase, making it even drier than it is now.

The researchers analyzed ocean sediment cores from the Horn of Africa dating back 200,000 years. The team collected samples from the core roughly every four inches (10cm). This represents periods of about every 1,600 years.

The researchers looked for chemicals called alkenones, which are made by a particular kind of marine algae. This chances in composition relative to the water temperature.

They also analyzed ancient leaf wax that had blown into the ocean, helping to determine the rainfall patterns.