Part Primate, Part Pig

In 1976, Richard Dawkins wrote: "Most of what is unusual about man can be summed up in one word: 'culture'."

Genetic differences between humans and chimpanzees would thus likely be explained by a theory of gene-meme coevolution. Or so I have assumed for a decade or so.

Now a rogue scientist has come up with a very different explanation for the differences between humans and chimpanzees. He substitutes "culture" with "pigs".

"Most of what is unusual about man can be summed up in one word: 'pig'. The hypothesis is that a pig and a great ape mated and produced viable offspring. Some of their genes persisted in the population and eventually came to dominate it. Their descendants are modern humans.

This is not a very new idea. Eugene McCarthy as been promoting it for over a decade. For a while. phenotypic similarities were the main evidence. However, now Eugene has performed a genetic analysis that he claims provides solid evidence for the theory. The paper is: "Human Autosomal Nucleotide Positions Differing from Bonobo Instead Match Pig".

It is an amazing, surprising result. If replicated it will likely turn much of our understanding of human evolution on its head. Eugene's data shows that the Y chromosome has a lot of pig influence, while the X chromosome doesn't have any. This implies that the pig males mated with monkey females - and not the other way around. The Y chromosome doesn't cross over, so it means humans basically have a pig's Y chromosome. How come nobody noticed this before? I don't know, but it does look as though the Y chromosome is similar to that of a pig. Various papers have pointed out its oddities.

The pig Y chromosome estimated to be 50Mb here. That is similar to human at 57 Mb. Different from chimpanzee at 25Mb. The conventional explanation is: more sperm competition in chimps generates selection pressure favoring small size. Another site says: ""Puzzlingly, in terms of shared genes and overall architecture, the human Y is more similar to the gorilla Y than to the chimpanzee Y even though human and chimpanzee have a more recent common ancestor."

The evidence from the sex chromosomes is interesting and it could be easy to verify. However the rest of the genome is where the main evidence lies.

Eugene's study needs to be reviewed and replicated - but it is looking as though this could be an important find for those interested in human evolution.

Update: Eugene checked - and the human Y chromosome is more similar to chimpanzee than it is to pig - according to his metrics. It is consistent with the hypothesis of the hybrid inbvolving a male pig - since the pig Y chromosome could still subsequently go extinct in the population.

For more on the gorilla-related evidence see here.