[PatrickHenry]

It means that, yes, most of our heritage came out of Africa recently but there probably was some interbreeding with the hominids who had fanned out earlier, including the neanderthals.

Not necessarily. This old "non-African" gene could have originated in Africa, but it might have been a local thing, and was mostly concentrated in the tribes that migrated out. The migrants took it with them before it had a chance to spread throughout Africa.

[VadeRetro]

Spoilsport!

If enough of these "ancient" genes turn up, your explanation is the first to fall.