I think there is mounting evidence for Model C, the trellis model of evolution:
Out-of-Africa versus the multiregional hypothesis
Broadly speaking, there are two competing hypotheses on the origin of modern humans: the Out-of-Africa hypothesis and the multiregional hypothesis. Both agree that Homo erectus originated in Africa and expanded to Eurasia about one million years ago, but they differ in explaining the origin of modern humans (Homo sapiens sapiens). The first hypothesis proposes that a second migration out of Africa happened about 100,000 years ago, in which anatomically modern humans of African origin conquered the world by completely replacing archaic human populations (Homo sapiens; Model A). The multiregional hypothesis states that independent multiple origins (Model D) or shared multiregional evolution with continuous gene flow between continental populations (Model C) occurred in the million years since Homo erectus came out of Africa (the trellis theory). A compromised version of the Out-of-Africa hypothesis emphasizes the African origin of most human populations but allows for the possibility of minor local contributions (Model B).
And Model C really blurs what it means to be human. Yes there were many human species over this time period all over the world that intermixed a great deal. Some had brow ridges and some had globular brains but it didn’t deter them from having a lot of sex.
