But and hybrid between a chimp and a pig: simply no way! Even creating a live pig-chimp hybrid is probably almost impossible, a fertile pig-chimp hybrid would be a miracle.
(That said, before you interpret this as me supporting the theory, please read my top-level comment)
"For my own part, curiosity has carried me away from my old idea of reality. I no longer know what to believe. Is it possible that so many biologists might be wrong about the nature of human origins? Is it possible for a pig to hybridize with a chimpanzee? I have no way of knowing at present, but I have no logical or evidential basis for rejecting the idea. Before dismissing such a notion, I would want to be sure on some logical, evidentiary basis that I actually should dismiss it. The ramifications of any misconception on this point seem immense." --from macroevolution.net
He says it would be possible and there's evidence in physiology. Saying there's no way or that it would be a miracle (and dismissing it for that) is showing a misunderstanding of evolution. Given enough time and enough tries, it could happen.
A bacterium becoming a mitocondrium within a cell is one of the most astounding miracles of life and scientists have never been able to reproduce it (and mind you, generations of cells come by far easier and faster than of chimps and pigs), yet it happened, perhaps exactly and only once, but it happened and that's why all animals exist.
I think, like the author, that some curiosity and imagination is never a bad thing. It's led to our most interesting discoveries.
1 people think hybrids are sterile, but they're not 2 people think hybrids don't occur in nature, but they do 3 people think only plants hybridize, but animals do to
From this basis, he concludes that a chimp-pig hybrid is plausible, and proceeds to lay out his theory.
The problem is the three facts he starts with are trivial compared to the obstacles raised by PZ Meyer. To take just one, there is the difference in chromosome number. In most cases, if a human ends up with the wrong number of chromosomes, it's a lethal condition. Or you end up with Down's syndrome. With one extra chromosome. The hybrid this guy posits has a dad with 38 chromosomes and a mom with 48.
I could argue that that's not a big deal. In the plant groups I study stranger things happen. But that's in plants. Primates, as I understand it, are much more sensitive to chromosomal abnormalities.
There are many logical, evidential reasons to discount this hypothesis. Again, check out the pz meyer post linked elsewhere. Claiming I don't understand evolution because "given enough tries anything is possible" is facile. Of course anything is possible. But what is probable here?
Sure the hybrid has parents wildly different genetically. But if two individuals who have a high chance of producing fit offspring may by chance produce unfit individuals, then we also agree the hybrid would have to have been a minimally fit individual by chance born from two parents who have a very low chance of doing so. A person with Down syndrome is not a catastrophe of nature, and not fundamentally a disease, such that through successive backcrossing (women with Down syndrome are usually fertile) it could theoretically produce a different kind of Homo that would be fit for some imaginary environment conditions. Or at least would still be a far more intelligent creature than all other animals we have on this planet.
This happens once, and you can make it a teachable moment. But when the scenario starts to repeat itself it undermines the effort you're putting into teaching real science.
If you assume that a hybrid is necessary for intelligent life (which is a crazy, unlikely, implausible assumption, I know) then it doesn't matter if it only happens in one out of a billion worlds, on the one world it does happen in, there will be intelligent people around to talk about how unlikely it is.
Now maybe it's not so implausible. Pigs are some of the smartest animals, and something weird happened a few million years ago to jump start human evolution such a crazy amount. Still seems pretty unlikely IMO though, but I'll raise my probability estimate of it slightly.