Neanderthals interbred with non African populations

[Anomalocaris]

and did not have very close contacts with dwellers of cold climate such as neanderthals

The range of HNS



is not strictly limited to cold climates, though. Frankly, they seem to demonstrate a wide range of adaptability and did so for 400,000 years during which the ice sheets advanced and retreated a couple of times.

But if we assume Neanderthal to have been a single species with gene flow throughout its range, then we would expect the same gene flow across the population of lice that might have infested neanderthals. So even if neanderthals in the south lived without clothing, the neanderthals in the north almost certainly wore tight fitting clothing at least part of year. So the northern neaderthals would, in winter, act as a conduit from head to crotch to ensure neanderthal lice remained one single species.

The fact that we haven't been infested with any single species of lice that can live both on our heads and our crotch suggests either we are biochemically sufficiently different so neanderthal lice can't live on HSS, or we did not have very close contact with neanderthals very often, and neanderthal lice didn't have many opportunities to make the successful jump onto us. So we continue to keep the two species of lice that we bred when we were back in Africa.