Some 75,000 years ago, something apocalyptic occurred that left relative few humans alive to carry on the species. Human evolution is believed to have begun some six million years ago. Despite the passage of so much time, the amount of diversity among the DNA of all humans is minuscule. The cause of this bottleneck is now believed to have been a massive volcanic eruption on the Indonesian island of Sumatra. A super eruption from the site of Lake Toba in Sumatra blasted out more than two hundred cubic miles of ash over an area of over a million square miles.