With regards to hominids other than Homo Sapiens perhaps. I collected to evidence for significant genetic barriers to hybridization with what I call humans below…
The evidence suggests that Neanderthals were not human. There are several categories of evidence for this, but I’d like to focus on the very strong genetic evidence which points to this conclusion after just one point from morphology.
Of course humans have been changing somewhat for a while. Our modern globular brain shape did not even work its way into our phenotype until after 36,000 years ago , a date which some would say was near or after the date Neanderthals went extinct. I am not even convinced that the physical brain is what truly makes us human. But to the extent that it is brain shape may be even more important than brain size. Hominid brain size did not change much in almost half a million years while what humanity has accomplished from the time modern brain shape occurred to the present is orders of magnitude greater than those of other hominid groups given that same amount of time with a similar brain capacity.
Scientists tell us that all living Eurasians have an average …
Most of the heat I got was for only considering our species to be human. It was hard to deny the rest because I was mostly just linking to studies.