Gene's epiphany came when he realized there's one animal that has all of the traits which distinguish humans from primates. 'What is this other animal that has all these traits?' he promiscuously postulates. 'The answer is Sus scrofa, the ordinary pig.'
To get there, Gene has to bypass a few laws of biology, like sterile offspring in hybrids. A jackass for example is sterile - the result of a mule mating with a horse. And those two creatures are nearly the same thing!
Gene's dream hook-up goes like this: the original pig-chimp coital congretio was followed by several other pig-chimp 'backcrossings', where the offspring of a given pairing lived among chimps and mated with them - becoming more like chimps and less like pigs with each new freak of nature
The 'monkey-fucks-a-pig hypothesis' as it's now referred to by critics gets the most heat when considering pigs and monkeys are not 'interfertile'. Even if the female chimp did do the nasties with a pig the pig sperm would ignore the monkey egg anyway.
So it kinda looks like Gene is gonna have to find another way to justify his paycheck.
