Probably a lot. First, neanderthals were closely related to Denisovans. In Denisova cave itself, both neanderthals & denisovans were found and even a first gen

Probably a lot. First, neanderthals were closely related to Denisovans. In Denisova cave itself, both neanderthals & denisovans were found and even a first generation hybrid. So.. you could call it a denisovan-neanderthal complex with various subpopulations over time and geography. The altai neanderthals have been suggested as a subspecies/type... so there are differences there. In europe and the middle east, there's a decent phenotypical distinction between early and late (classical) neanderthals. The earlier type was less distinctively neanderthal... kind of more sapien looking. Later populations developed that distinctively bony face. ..Sapiens too, probably. We descend mostly from a small population of sapiens, but that doesn't mean other populations didn't exist. They just don't have descendants. For example, modern europeans have a relatively homogenous, low level of neanderthal DNA. At different points of history, certain populations could have ben 25% neanderthal... and genetically distinct from other groups. This is all normal mammalian population dynamics. Modern Sapiens are the unusual ones. We went through a genetic bottleneck and lost a lot of diversity.