According to proponents of the Toba catastrophe theory , the climate in non-tropical regions of the earth experienced a sudden freezing about 70,000 years ago , because of a huge explosion of the Toba volcano that filled the atmosphere with volcanic ash for several years . This reduced the human population to less than 10,000 breeding pairs in equatorial Africa , from which all modern humans are descended . Being unprepared for the sudden change in climate , the survivors were those intelligent enough to invent new tools and ways of keeping warm and finding new sources of food ( for example , adapting to ocean fishing based on prior fishing skills used in lakes and streams that became frozen )
Toba catastrophe theory
Toba catastrophe theory
Evolution of human intelligence