Jonathan Marx and Jerry Coyne recently had an online spat on the question “Are humans apes?” (Marx says no, Coyne says yes; see also Hawks, who says no.) I offer my own solution below, after talking about Linnaeus and biological categorization.
There’s a branch of cultural anthropology that studies “folk biology,” also known as “ethnobiology,” which is (among other things) about how different groups classify living things. Folk biological categories don’t vary randomly across cultures; there are some general principles at work. A quick summary: the basic level of categorization is roughly the genus. American folk genera include oak, crow, and fox (although urban Americans are often lousy at folk biology). Many peoples, and most hunter-gatherers, only take categorization down to the genus level. Others (especially horticulturalists) take it down to the species level, often with two part names (red oak, silver fox). Going toward more inclusive groups, genera are lumped together in larger, intermediate-sized, non-overlapping categories (palm, hawk), which belong in turn to the more inclusive level of “life forms”: (bird, snake, fish, tree, grass/herb).
From an anthropological perspective, Linnaeus’s famous scheme of classification is an elaboration of these universal principles, with more species and more taxonomic levels (the famous Kingdom, Phylum, Class, Order, Family, Genus, Species).
A version of Linnaeus’s scheme served evolutionary biologist well for centuries. But starting in the later twentieth century, many biologists turned to another approach that was claimed to be a better fit for evolutionary principles: According to cladists, the classification of living things should be based on clades: groups containing all and only the descendants of an ancestor. This requires overturning or revising many familiar categories. For example, monkeys are not a clade, since Old World monkeys are more closely related to apes (including humans) than to New World monkeys. Reptiles are not a clade, since crocodiles are more closely related to birds than to lizards and snakes. Fish are not a clade, since lungfish are more closely related to amphibians and reptiles than to most other fish.
After some bitter disputes. cladists seems to have won the battle among scientists. But cladism has made less headway among non-scientists. In Naming Nature: The Clash Between Instinct and Science, Carol Yoon argues that cladistics is just too much at variance with the way the human mind understands biological categories. Most people are never going to take to cladistics any more than they’re going to take to twelve-tone music, or Loglan. So different answers to the question “Are humans apes?” reflect disagreement about how far we can or should bring folk categories in line with the austere logic of cladism. Apes, including humans, are a clade. Apes, not including humans, are not (since chimpanzees are more closely related – but not more similar – to humans than to gorillas).
I suggest a compromise. Folk categories like ape, monkey, reptile, and fish, defined by shared ancestral traits, are useful, even if they aren’t clades, defined by shared derived traits. But the concept of a clade is also important one for biologists. So maybe when we want to talk about the clades associated with folk categories, why don’t we use a prefix – the Scottish Mac, Irish O’, or Hebrew/Arabic ben/bin. (Any of these will serve.) So human beings are not apes, monkeys, reptiles, or fish. But we are MacApes, O’Monkeys, Ben Reptiles, and/or Bin Fish.