Chimp + Pig = Human?

I had to read it several times, searching for clues that it was intended as a joke…

It wasn’t.

An article posted on phys.org today is entitled, “A Chimp-Pig Hybrid Origin for Humans?”

Dr. Eugene McCarthy, a geneticist, has built a case for his theory of human origins, a theory that is based upon repeated hybridizations (different species mating and producing novel offspring) over many generations. He suggests that these cross-species interludes likely involved a male boar and a female chimp, with the resulting offspring being nurtured by the mother chimp.

McCarthy has arrived at his conclusion not by genetic evidence (which he believes is relied on too heavily) but by extensive anatomical comparisons:

The list of anatomical specializations we may have gained from porcine philandering is too long to detail here. Suffice it to say, similarities in the face, skin and organ microstructure alone is hard to explain away. A short list of differential features, for example, would include, multipyramidal kidney structure, presence of dermal melanocytes, melanoma, absence of a primate baculum (penis bone), surface lipid and carbohydrate composition of cell membranes, vocal cord structure, laryngeal sacs, diverticuli of the fetal stomach, intestinal “valves of Kerkring,” heart chamber symmetry, skin and cranial vasculature and method of cooling, and tooth structure. Other features occasionally seen in humans, like bicornuate uteruses and supernumerary nipples, would also be difficult to incorporate into a purely primate tree.

In other words, we have many features that are pig-like (porcine) rather than chimp-like.

What I find fascinating about McCarthy’s theory and the evidence he uses as support, is that it calls into question the currently popular Neo-Darwinian theory of slow, gradual descent with modification, where species slowly branch off in a tree-like pattern. How so, you ask? McCarthy’s theory postulates a web-like pattern where species cross with each other and perhaps back-cross repeatedly. Also, his work indirectly highlights the fact that humans have an impressive list of non-chimp-like physical characteristics that would have to emerge much more quickly than the Neo-Darwinian process alone is capable of producing. The number of necessary mutations to get from a chimp-like common ancestor all the way to modern Homo sapiens is huge–a situation illustrated by the (very partial) list of characteristics that need explaining. Coupled with what we know about mutation rates the situation seems pretty hopeless. Hence the need for a new hypothesis that introduces a way to speed up this morphological (structural) change:

McCarthy has done extensive research into the broader issues, and shortcomings, of our currently incomplete theory of evolution. As the increasing apparent, magnificant [sic], speed with which morphological change can occur continues to present itself for us to comprehend, the standard theory of random mutation followed by slow environmental selection, seems to stall.

Note how evolutionary change is automatically assumed and a glaring weakness of current evolutionary theory is admitted.

The pattern in the hominid and human fossil record shows strong discontinuities, with distinct species appearing suddenly and later going extinct. Furthermore, our closest alleged ancestor, Homo heidelbergensis, is quite different from Homo sapiens, anatomically speaking. Theorizing hybridizations as the culprit for rapid, leaping change in the human lineage is extremely interesting, to be sure. Plausible? That’s highly doubtful when the past several centuries of field observation are taken into account. Fertile hybrids in the animal kingdom are exceedingly rare. We don’t even see offspring at all except in rare cases where very similar species cross, such as the horse/donkey hybrid (mule) and the tiger/lion hybrid (liger). What we do not observe–ever–is offspring of two very different species, such as the suggested chimp and pig hybridization.

But, when one hypothesis about origins begins to lose plausibility, one must come up with another. As always, the design hypothesis for human uniqueness is avoided like the plague. We might as well sit back and be entertained.