Researchers at Stanford University have concluded that humanity was nearly wiped out during a global drought 70,000 years ago. Their calculations indicate that at its dearth, there may have been as few as 2000 humans left. Anthropologists believe the climactic conditions may have forced some of the remaining human tribes together for survival, an act that helped to repopulate the species. By studying mitochondrial DNA, the researchers were able to trace back ancient humans and revealed another discovery, not only were humans nearly extinct but there were almost two distinct species of human. It is believed that human tribes split roughly 150,000 years ago and lived in complete isolation from one another for nearly 100,000 years. The findings are the result of the Genographic Project committed to discovering the origin of humanity.

Mitochondrial DNA is a DNA sequence _within_ a cell that contains the instructions for the cellular activity of energy conversion. This DNA is passed down strictly via a maternal line which has allowed a science of genetic anthropology to trace humanity's ancestry through time. Earlier this year it was discovered that 95% of all Native Americans are descended from only six maternal mitochondrial DNA lines. Following the ancestral trail further back reveals that humanity is descended from a single maternal line dating back 200,000 years to Africa.