Homo sapiens evolved about 200-150,000 years ago in Africa, but our story as a species stretches back much further than that with early human ancestors. And the evolution of Homo sapiens is itself a tangled tale, full of unanswered questions and gothic family melodrama. Here are a few facts you may not know about the human evolutionary story.
By Annalee Newitz – io9
1. Early human beings left Africa over 1 million years ago
Most of us have heard the story about how Homo sapiens poured out of Africa into Europe and Asia starting about 80,000 years ago. What you may not realize is that our ancestor, Homo erectus, had been taking the same routes out of Africa on and off for over 1 million years. In fact, when Homo sapiens left Africa, they would have encountered other humans who looked very much like themselves – these would be the descendents of the common ancestor we share with Neanderthals, as well as the descendents of Homo erectus. All of these people were early humans. And they had been wandering around Eurasia for hundreds of thousands of years.
2. Humans have incredibly low genetic diversity
Humans are among the least genetically diverse apes, mostly because we all appear to be descended from a small group of humans who lived in East Africa. To describe genetic diversity, population geneticists use a measure called „effective population size.“ Put extremely simply, effective population size is how many people you would need to reproduce the genetic diversity of our full population. For humans, this number hovers around 15,000 individuals, which is pretty insane when you consider our actual population size is 7 billion. As a point of comparison, some species of mice have an effective population size of 733,000.