Only those of very limited imagination would assume that any of three different Homo species are “inferior” to any of the other. Tigers, lions and leopards are all different species of the genus Panthera [0], but nobody says that one is inferior to the other.

Just like the Homo species, different Pathera species can interbreed [1]. The most interesting observation is that it appears that Neanderthals and ancient Africans (we don’t seem to have a good short name for the Homo species that arose in sub-Saharan Africa) follow Haldane’s Rule [2], where only male Neanderthals and female ancient Africans were able to produce fertile offspring [3].

0. https://en.wikipedia.org/wiki/Panthera

1. https://en.wikipedia.org/wiki/Liger

2. https://en.wikipedia.org/wiki/Haldane%27s_rule

3. http://www.hypothesisjournal.com/?p=932