About 100,000 years ago, tropical East Africa has been through several bouts of exceptional droughts. The level of Lake Malawi, one of the deepest lakes on the planet had diminished to about 600 metres below its current level of 706 metres. According to a group of American scientists headed by Andrew Cohen of the university of Arizona, this is the lowest level the lake ever had.
Pollen are extremely rare in sediment core samples corresponding to a time span from 90,000 years ago to 125,000 years ago. This shows that the region was virtually a desert. The lake was then filled with micro-algae and invertebrates that can today be found in shallow and muddy waters.
It was already known that the Kalahari desert was extended towards the north and that the Sahel was extended towards the South during this period, but it was not suspected that this same phenomenon had also affected tropical Africa.
According to Le Figaro
, a leading French newspaper, The scientists think that these dramatic ecological changes may be the direct cause of the emigration of Homo sapiens from the African continent.