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PNAS finally published one of the two sets of ecological explanations for the Out-of-Africa theory in “East African megadroughts between 135 and 75 thousand years ago and bearing on early-modern human origins.” The second publication “Ecological consequences of early Late Pleistocene megadroughts in tropical Africa” also came out earlier this week.

If you didn’t catch this the first time I brought it up in September, the quick one sentence summary is these studies focused on evidence of ancient megadroughts from sediments cored from the bottom of Lake Malawi and comparing those findings with similar records from Lakes Tanganyika and Bosumtwi.

After a whole lot of logistical challenges, the team extracted a series of cores, some as much as 1247 feet (380 meters) long that spanned  hundreds of thousands of years. Cores like these give a high level of resolution into the prehistoric ecology. Often oceanographers and climatologists use cores like these to study the diversity of plankton, aquatic invertebrates, etc. to reconstruct the flora and fauna at particular point in time. The authors found indicators of drought present in the cores from sampling species of invertebrates and plankton that only live in shallow, turbid, algae-rich waters — a situation very different from the deep, clearwater lake that Malawi is now.

This would have been a significant change to East Africa’s ecological make up… What was once tropical Africa was extraordinarily dry about 100,000 years ago, facilitating the migration of humans out of the Africa.