Before the dawn of civilization, humans lived in sub-Saharan Africa. Eventually, these primitive people migrated out of the continent, spreading to the Middle East, Europe and Asia, compelled by drought to seek a more accommodating environment, according to a study published in 2007 in the Proceedings of the National Academy of Sciences.
Between 135,000 and 90,000 years ago, Africa transformed from lush tropical country to an "arid scrubland," researchers discovered after analyzing sediment cores from Lake Malawi, one of the world's largest and deepest lakes, which borders Malawi, Mozambique and Tanzania. A reflection of how severe the droughts were, Lake Malawi's water level dropped at least 600 meters (1,968 feet), leaving shallow waters full of algae, instead of the deep, clear waters seen today.
Little evidence exists of human populations, which likely crashed, during this time. Beginning 70,000 years ago, traces of human activity sprout up once again, along signs of a northward migration.
Ancient Stones Hint at How Humans Migrated Out of Africa