This guy is a geneticist that thinks chimpanzees bred with pigs to create hybrids that eventually became the humans we are today. I love this side of the internet.
Entertaining site, and surprisingly informational in tone, despite the ridiculousness of most of the cases.
I do wonder how much research goes into this topic. The common knowledge seems to all boil down to a single sentence: Only same-species couples can reproduce, except a few cases of same-genus couples, but their offspring is infertile. But how much of this is theoretical, and how much is a result of experimentation (not necessarily full blown Moreau experiments - just creating a viable zygote)? If there's little experimentation, is it because we're just so confident in the theory, or is it because of morality or taboo?
This “definition” can so easily be reduced to the absurd by simply going back in time in steps to the common ancestor of, say, humans and dogs, and then going up again, to then by transitivity prove that human beings and dogs are the same species, yet they cannot reproduce together.
The classification of “species” is entirely arbitrary, any “definition” of it offered is shallow and pædantic.
We know that different animals have different numbers of chromosomes. For example, humans have 46 and chimps have 48 even though our common ancestor is relatively recent. So at some point there must have been successful reproduction between two apes that had different numbers of chromosomes, no?
So what are we actually looking at with some of these? Other than convincing looking fakes, heavily deformed offspring that resemble a bit of both species?
I've read his two-volume book on mammalian hybrids. He guides the reader through some thousands of reports, and some suprising commonalities can be seen that are hard to discount, even if specific cases may seem unlikely.
https://www.google.com/search?q=jackalope+taxidermy&tbm=isch