His discussion includes exploration of physical features shared between humans and pigs, including “lightly pigmented eyes, in shades of blue, green, and tan,” which “are never found in chimpanzees or orangutans.” So my blue eyes make me more pig-like than other people, perhaps.
Much of this is far too technical for me to really understand. Anything we don’t share in terms of physical characteristics with apes can presumably be traced to pigs. This is taken to be of such significance as if all that distinguishes human beings from other animals is the particular arrangement of material parts.
But it does remind me a bit of the exposure of the limits of human understanding illustrated in the anecdotal exchange between Plato and Diogenes of Sinope. Plato was working with a definition of a human being as a “featherless biped.” Diogenes plucks all the feathers off of a chicken, and returns to Plato, triumphantly exclaiming: “Behold, a man!” At this, Plato modifies his definition a bit: a human being is a featherless biped, with broad, flat nails.
I get the sense that Diogenes’ response to McCarthy would be to come to us with a pig in one hand and an ape in the other, and proclaim: “Behold, a man!”
This might require us to move beyond merely materialistic definitions of the human being.