Does this mean that humans and Neandertals were distinct species who intermixed by hybridization?
I wrote about that question last year, concluding: There will never be any tidy solution to the species problem, because all species have unique evolutionary histories and constraints. Given these difficulties, the species status of archaic Homo populations is basically an intractable problem. That is, I am happy to suggest that archaic Homo populations correspond to classical subspecies, and as far as I know, no evidence strongly contradicts that position. But I can recognize that some people will never agree with this assignment. And from the perspective of their evolution, it just doesn’t matter. Evolutionarily important gene flow occurs between mammal species, subspecies, and populations. The last sentence is the most important point. Those who want to put Neandertals into a distinct species (Homo neanderthalensis) generally believe that there was no evolutionarily significant gene flow between them and modern humans. But the opportunity for evolutionarily significant gene flow is
