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“Recent work has provided new insights into gene flow from the ancestors of modern humans into Neanderthals 29, 30•. Specifically, it was previously inferred that an early out-of-Africa dispersal resulted in gene flow from a modern human group into Neanderthals between 200 and 250kya 31, 32, 33. However, Li et al. [30•] suggest there was another early out-of-Africa dispersal, approximately 100kya, that also resulted in gene flow from modern humans to Neanderthals (Figure 1). These data suggest that modern humans have dispersed out of Africa multiple times, resulting in recurrent admixture between humans and Neanderthals throughout much of modern human history.”
So humans were out of Africa 250k to 100k years ago and those populations were removed from the since extinct archaic hominids that were still roaming around Africa. So there were many thousands of generations inside and outside of Africa that were intermixing with different hominids until who knows when. Diffusion occurred back and forth as well but there were some divergences and mixtures weren’t consistent.