There is compelling evidence for the "recent African origin of modern humans":
https://en.wikipedia.org/wiki/Recent_African_origin_of_modern_humansThis theory is supported by fossil and genetic evidence.
The main competing theory is "multiregional origin of modern humans." Since the 1980s, this theory has fallen out of favor, because it is not supported by the genetic evidence.
One of the more famous discoveries that supports the "out of Africa" theory is "mitochondrial Eve." Mitochondria are organelles that carry separate genetic information from the nucleus; you inherit all of your mitochondrial DNA from your mother. Based on studies of mitochondrial DNA, it appears that all humans can trace a matrilinial line back to a single woman, who lived in East Africa between 100 and 200 thousand years ago.
Edit: wait, did I just post in a thread called "African Americans: A Growing Danger"? wtf is this?
Edited 11/16/2015 22:21:32