Wikipedia's Multiregional hypothesis and Single origin hypothesis.
The multi-regional hypothesis suggests that each group of modern humans evolved almost independently from each other from about 1.5 million years ago with a certain amount of interbreeding between the groups to explain why we are still very similar. The single origin hypothesis which is the most popular of the two, suggests that Homo sapiens started to move out of Africa between 100,000 years ago and 80,000 years ago moving out across the world replacing and not interbreeding with Homo species already there.
There are other theory's as well, such as the Polygenism theory and Hybrid-origin theory although there seem to be little or no evidence for them. So seeing as there are many people here who seem to be quite knowledgeable about biology and evolotion in particular, i would like to hear your opinion on the various theory's. Thank you.