03 January 2008

Ape Taxonomy Is Confusing

Homininans, including us humans, are a type of hominin. Hominins are part of Homininae. Hominidae includes hominines. These are all subsets of Hominoidea.

Confused yet? You should be. Welcome to the not-so-wonderful world of typological, ranked taxonomy.

Traditionally, taxonomy had little to do with how organisms were actually related (Linnaeus having preceded Darwin by a good century). Taxonomy was just a way of sorting specimens: these ones go in this box (a species), and the little box goes in this bigger box (a genus), and the bigger box goes in this even bigger box (a family), and so on.

Eventually a typological system arose from this: one specimen (ideally) would be the standard, the archetype, the name-bearer for a given little box. One little box would be the "type" for a larger box, and so on. The box sizes were also strictly regulated: species, genus, family, order, class, phylum/division, kingdom. Eventually, new intermediate sizes, or ranks, were also added: subgenus, subfamily, superfamily, infraorder, suborder, etc.

Several taxonomic codes arose to govern this style of taxonomy, primarily the ICZN for fauna and the ICBN for flora. To simplify matters, they mandated that the name of a type genus should be used with the appropriate suffix for some of the taxa that include that genus. The codes don't agree on which suffixes to use for ranks (for example, the ICZN uses -idae for families while the ICBN uses it for subclasses), but they are standardized within each code.

Under the ICZN, our own taxonomy below the ordinal level looks like this:
RankTaxonEnglish vernacular form
SubgenusHomo (Homo)
SpeciesHomo sapiens
SubspeciesHomo sapiens sapiens

Anyone whose skin isn't crawling by now isn't paying attention.

Not only are these names comically and confusingly similar, but they're ambiguous. "Hominidae" means "the family that includes Homo", but what constitutes a "family" is entirely up to the whims of the taxonomist. As I've discussed on this blog earlier, some researchers restrict to to Homo and a few close, extinct relatives, while others have included all great apes as well, or even all apes.

Recently there has been a movement to coöpt these names into a phylogenetic framework. Something like this is emerging as a consensus (extinct taxa omitted):

|--Hylobatidae (gibbons)
| `--Pongo (orangutans)
| `--Gorilla (gorillas)
| `--Pan (chimpanzees, including bonobos)
`--Homo sapiens (humans)

In some ways this is a good scheme, but it has two big problems: 1) the Homo-typified names are still all horribly similar, and 2) many people still use those names in the more traditional way, where, for example, Gorilla, Pan, and Pongo are not in Hominidae.

So here's a brainwave: why not just think of new names for these clades? Seriously!

We already have some good vernacular names as a basis: "apes" for Hominoidea, "great apes" for Hominidae, and "African apes" for Homininae. Admittedly there's not a convenient term for the chimp-human crown group (besides "the chimp-human crown group", of course). Maybe something like "hunting apes" (humans and common chimps are the only apes to go on hunts, I think) or "sexy apes" (humans and bonobos are the only apes to engage in certain sexual positions and activities). Translate these into Latinized Greek and we get:

|--Hylobatidae (gibbons)
|--Pongo (orangutans)
|--Gorilla (gorillas)
`--[insert clever name here]
|--Homo (humans)
`--Pan (chimpanzees, including bonobos)

Isn't that much nicer? All of these could be defined as crown groups (except for Homo).

Well, just a little dream of mine, anyway....


  1. Personally I like the similar names. It keeps everything organized.

  2. Yeah, it's not a bad idea in theory, but in practice it gets really, really cumbersome. Like if I said, "Hey, draw me a basal hominin," you'd have to 1) remember which rank that meant, and 2) know how extensive I like my ranks to be.

    The latter is especially a problem--just try using the word "Hominidae" in a technical discussion and watch as different people assume you're referring to very different groups. But something like "Afropithecoi", that could be pretty unambiguous.

    It's even worse in botany, where the mandated suffixes go all the way up to divisions (=phyla in zoology). Magnoliidae and Magnoliaceae and Magnoliales and Magnoliopsida and Magnoliineae ... ack!!!

  3. 'Cause we're punks.

    No, seriously, don't ask me, ask the Greeks. I dunno, maybe there's another way the Latinize it (-pitheci? -pithecae?).