Bradshawfoundation.com has an amazing graphic history of Homo Sapien’s migration out of Africa. The story begins with one female in one tribe in east Africa, from which we all descend. The plot develops to have us migrating, getting wiped out by weather, and then migrating again along coasts to reach Vietnam, when a volcano erupts in Sumatra. The volcanic ash fills the sky, creating a 6 year dark winter, and a 1000 year ice age. The ash falls to bury Inidia, in some places more than 5 meters deep. Only 10,000 adults survive. The hardy 10,000 set up camp and drop babies all over the place. Occasionally the land surrounds tribes with ice and kills them, but enough of us remain to populate the globe and plan warfare.
Projecting our history further, Jay Hanson at dieoff.org speculates the timeline of descent into the post industrial stone-stage , based on oil and mineral resource depletion. Not likely, but he makes the point that our resource use must change or there will be broad industrial collapse, meaning large groups of people will starve. We could still avoid the catastrophies, if money and power shift away from Oil. Maybe the next Bill Gates will be working on photovoltaics.