The hypothesis that humans descended from chimp-pig hybrids can be denied on the following points.
- Hybrids between different orders of mammals are very rare due to the genetic differences and differences in chromosome number.
Despite McCarthy's suggestions to the contrary, reports of hybrids between different orders of mammal, though, are, literally, incredible. His suggestion that the platypus is the result of hybridization between mammals and birds – an even bigger ask – seems to rest on a misunderstanding of the inheritance of chromosomes. Although some of the genetics of platypuses seems birdlike, this is much more consistent with its primitive state, and a mark of a shared inheritance between birds and reptiles (preserved in primitive mammals) than direct evidence for miscegenation. Source: No, Humans Are Not Chimp-Pig Hybrids
- No genomic evidence is currently present for the chimp-pig hybrid hypothesis. There is also no evidence of the occurrence of similar genetic material from both parents in the hypothesized chimp-pig hybrid which will confirm or predict the success of a hybridization event.
He offers no such evidence, possibly because every published genomic study of pigs, human, and non-human apes suggests that the former are only distantly related to the latter two. Pigs and apes are both placental mammals, but not very related to one another. So their last common ancestor may have been sometime in the late Cretaceous, 70ish million years ago. The claim that the gametes of a pig and a chimp would be compatible in any sort of way requires evidence that other such large crosses are possible. Source: No, Humans Are Not Chimp-Pig Hybrids.
- A major genetic difference between humans/higher apes and pigs is that they do not share a working version of gal-transferase.
That gene is called galactose-alpha-1,3,galactotransferase — gal-transferase for short . All mammals except humans and higher apes have a working version of gal-transferase, which coats cells with an antigen (a molecule that our immune system reacts to). This means if pig tissue is transplanted into humans our immune system will mount a drastic rejection response as our bodies detect the antigen and attack it. Pigs weren't part of that lineage. This is a fact, established by comparative research on genomes. Humans are closely related to chimpanzees (and gorillas), with whom we share this missing gene. We simply aren't particularly close, genetically, to pigs. And that means we aren't the offspring of cross-species sexual relations. Source: Pigs and Chimpanzees Living in Sin?
TL;DR: Referring to Dr Du and Prof Feng, physiological similarities between pigs and humans was maintained at a genetic level of 84% homology between the two species. However, detailed analysis showed that there were several important differences.
The analysis of the pig genome, published in Nature last year and available free does reveal shared similarities with humans – and why not? It shares similarities with many other mammals, too. But there seems no especially close relationship between the pig genome and the human genome, which is what one would expect had some hybridization occurred in the past few million years. Source: Evolutionary theory that a chimp mated with a pig is pure sausagemeat