The inside of Africa, having never met a Neandertal,

The partial replacement model of human origins states that modern humans expanded out of Africa before 100,000 years ago. Rather than simply out-competing and thereby replacing the premodern humans they encountered, this model suggests that modern humans also interbred with premodern humans. Through a complex interaction of hybridization and replacement, modern humans would have gradually established themselves as the only hominid species (West LA College, 2018).While this model suggests a degree of co-existence between the modern and premodern human populations, the exact extent and nature of that coexistence remains more or less mysterious. However, the degree of interbreeding between these groups appears to have been modest. Recent findings from DNA indicate that interbreeding ranged from 1 to 4 percent in populations outside of Africa (Jurmain, R., Kilgore, L., Trevathan, W., Bartelink 2017 p. 289). The modern humans inside of Africa, having never met a Neandertal, would hardly have had the opportunity to breed with one. This is reflected in the lack of Neandertal DNA in contemporary Africans.The genetic evidence that modern humans interbred with Neandertals and Denisovans strongly supports a partial replacement model of human origins. In combination with the fossil record, the presence of premodern human DNA in non-Africans and the lack of this DNA in Africans forms an almost incontrovertible argument that modern humans first emerged in Africa and then parts of this population migrated off the continent. When these modern humans traveled into areas where premodern humans lived, the DNA shows that they must have interbred. Short of alien intervention, divine interference, or some sort of incredible gene transfer technology somehow emerging from the Mousterian period, I can think of no way around it: Some modern humans exchanged DNA with premodern humans and they did so in the old fashioned way. I’m convinced.But, having said that, a possible alternative to the partial replacement model of human origins is the regional continuity model. It postulates that all humans following Homo erectus are Homo sapiens. (Jurmain et al 2017 p. 287) The regional continuity model claims that modern humans evolved in different regions (West LA College, 2018). It explains the similarities in morphology between these different groups of humans through a significant level of gene flow and migration between Pleistocene populations. This would have prevented speciation (Jurmain et al 2017 p. 287). If we, like this theory’s advocates, grow progressively less dogmatic in light of recent and accumulating evidence, and acknowledge that humans evolved first in Africa (Jurmain et al 2017 p. 287), we would still need to see transitional fossil evidence of humans more or less simultaneously evolving in continents aside from but including Africa. (West LA College, 2018). Given the genetic evidence against this model, I would say that we would have to see quite a few of these fossils.