The strong Out of Africa hypothesis (Stringer) posits that modern humans appeared in a subpopulation of Homo Erectus, perhaps as a new species, and spread continuously over much of the Old World. The new population replaced those living in other areas as they spread. The weaker Out of Africa hypothesis posits again that modern humans appeared in a subpopulation and spread slowly over several tens of thousands of years, then later expanded from separate daughter populations bearing modern technologies such as those of the African Late Stone Age or the European Upper Paleolithic. The Multiregional hypothesis (Wolpoff) posits that the entire Homo Erectus gene pool contributed to the gene pool of modern humans. Gene flow kept these Old World populations connected as one evolving species.
In his monthly article for Natural History in February of 1994, Gould wrote about human origins. I would like you to consider this portion of his article called "In the Mind of the Beholder" (Natural History, vol. 103, No. 2, February 1994, pg. 14-23.)
Origins in a single place is the expectation of ordinary evolutionary theory, and utterly unsurprising. Species are unitary populations of organisms that split off from their ancestral populations in a limited part of the parental range. Species arise as historical entities in particular places and then spread, if successful, as far as their adaptations and ecological propensities allow. Rats and pigeons live all over the world, just as humans do. Yet we are not tempted to argue that rates evolved in parallel on all continents simultaneously. We suppose that, like most species, they arose in a single region and then spread out. Why, then, does origin in a single place surprise an entirely idiosyncractic, and unusual multiregional hypothesis, and then proclaim it orthodox and expected?
I can only suppose that we want to segregate humans off as something special. We wish to see our evolution, particularly, the late expansion of our brain to current size, as an event of more than merely local significance. We do not wish to view our global triumph as so fortuitously dependent upon the contingent history of a small African population; we would rather conceive our exalted intellect as so generally advantageous that all populations, in all places must move in adaptive unison toward the same desired state....
Finally, I regard each species as a contingent item of history with an unpredictable pathway. In short, all my nonsurprises are coordinated by a world view that celebrates quick and unpredictable changes in a fossil record featuring lineages construed as largely independent historical entities. I should also add that I find such a world stunning and fascinating in its chaotic complexity and historical genesis - and I happily trade the comforts of the older view for the joys of contemplating and struggling with such multifarious intrigue.