More than kin and less than kind

As Huxley observed in Man's Place in Nature, Darwinism fundamentally alters our relationship with the rest of the natural world. To say that, after Darwin, we are animals does not make this transformation quite clear enough. Pre-Darwinian thinkers from Aristotle to Linnaeus said the same. For them, it was a matter of taxonomy. After Darwin, it is a matter of kinship. Focussing narrowly on us, on human beings, we are now properly animals by nature as well as by kind. This is widely recognised.

What is not so widely appreciated are the implications for how we should think about them, that is, about other animals. Since Darwin, that category (nonhuman animals) has ceased to be a natural kind at all. Chimpanzees are more closely related to humans than they are to gorillas or orang-utans, let alone to fish. The six million years and a quarter of a million generations that have passed since our bloodlines parted company is as nothing to the close-on 400 million years and millions of generations that have gone by since any ancestor of ours could reasonably be called a fish. Even so, we (humans and chimpanzees) are more closely related to some of the animals we call ‘fish’ than those fish (specifically lungfish and coelacanths) are to any other fish currently alive. We can go on and on, expanding the category ‘ourselves’ to include each new set of cousins we encounter as we trace our genealogy back in time.