In his talk on mental models of the structure of the world, Josh Tenenbaum talked about how people think of animals as being classified in a tree structure, and how this structure might differ from those implied by different scientific models. This kind of thing:

Anyway, as an aside, Tenenbaum pointed out that, although the tree structure seems so natural to us, it doesn’t have to be this way. He noted that, traditionally, creatures have been organized into a linear “great chain of being” rather than as a tree structure. Then I realized . . . that’s how I think of the animal kingdom. It’s how we learned things in 9th grade biology. At the bottom are single-celled animals (amoebas and so forth), then gradually through the invertebrates, then the vertebrates, starting with the fish (with the sharks at the bottom because of their primitive structure), then amphibians, then reptiles (amphs are lower than reps because of being more fish-like and primitive, I think), then birds (higher because they’re warm-blooded), then animals, with primates at the top and, well, you know what’s the #1 primate . . .

Anyway, only when sitting in Tenenbaum’s talk did I realize that I’d swallowed this whole great-chain-of-being formulation without even thinking about it. The assumption is that every invertebrate is lower than every vertebrate, that the most complicated bird is lower than any mammal, that all plants are lower than all animals, etc. It’s still hard for me to shake this mode of thinking.

I guess it’s a good thing I’m not a biologist. (I did publish in the Journal of Theoretical Biology once, but we all know that knowledge of biology is not necessary to publish in that journal.)