The researchers cautioned that interbreeding between modern humans and other lineages of humans might influence the results of this new study. For example, instances of interbreeding with the now-extinct Denisovan lineage might have introduced ancient genes into certain modern human groups, perhaps making them look as if they left Africa earlier than they actually did.
“Our study did not specifically test for hybridization with archaic humans, and, of course, it is possible that such admixture could contribute to our results,” Harvati said. “We feel, however, that the very low levels of admixture that have been proposed are not sufficient to drive our findings.”
The researchers said continued fieldwork and genetic advancements might help confirm this model of multiple, relatively isolated waves of migration.
“The story of human evolution tends to be simplified,” Harvati said. “However, more complex models, such as multiple dispersals versus a single dispersal out of Africa, gain strength as more data and new methods become available.”
Waves and waves of hominids
Early Humans Migrated From Africa Far Earlier Than Previously Thought, New Study Suggests
The Committee to Nuke Elysium 