[Coyoteman]

Or, rather than the movements of whole populations, the trail of girls traded from tribe to tribe over thousands of years.

Humans trade the girls.

Right, but not when a group is migrating into an unoccupied territory. Then there is nobody to trade with.

[muawiyah]

"Over thousands of years" ~ even the furthest flung tribe has somebody to trade with back up the trail.

It happens. It distorts the information.