Triadomany?

Interesting material on threefold divisions' having been taken curiously far in past anthropology was recently deleted by some editors from Wikipedia's "3 (number)" article. It lacks references but is, I thought, worth preserving, but I didn't know where, but then I thought, why not here? (The reason for the deletion was not the lack of references but the editors' desire to strip the article down).

One really would little expect the evolution of kinds of primates or any living thing to exhibit a pattern of threefold division. But maybe it really did seem that way for a while with primates, as the material's original writer suggests (I myself, before its recent deletion, did some mostly stylistic and link-embedding later edits of it at Wikipedia). As a four-ist myself, I would not expect a pattern of fourfold division in biological evolution either! Peirce, of course, had a few things to say about triadomany - in "Triadomany" - wherein he argues that trichotomies are not to be expected to abound in natural history, and that logical division is to be distinguished from, among other things, genealogical division; the text as rendered by the Collected Papers' editors ends with his noting, with a kind of twinkle in his eye, Huxley's division of vertebrates into Ichthyopsida, Sauropsida, and Mammalia.

So here it is, discarded from Wikipedia:

Anthropology

Attempts to recognize tripartite patterns in human evolution were somewhat popular in the early-mid 20th century. Today, with new knowledge about the fossil record and phylogeny, they are all but refuted. However, one must wonder why there ever was a recurring predilection for a tripartite organization instead of some other pattern, whether or not a specific enumerative identity (such as the "three") presented itself.

With the realization that the Bonobo represents another and very distinct chimpanzee, humans are instead being referred to as "third chimpanzee", as among living creatures they are most similar to the Bonobo and Common Chimp.

• 3 distinct species of the genus Homo: 1. Homo habilis "capable man". 2. Homo erectus "upright man". 3. Homo sapiens "wise man".
  • But many additional species are now known.
• 3 distinct species of the genus Paranthropus: 1. Paranthropus robustus. 2. Paranthropus boisei. 3. Paranthropus aethiopicus.
  • But the validity of Paranthropus, although it is possible, has never been unequivocally proven.
• 3 Proconsul species: 1. Proconsul africanus. 2. Proconsul major. 3. Proconsul nyanzae.
  • But P. heseloni has been described since; and the genus Proconsul might not be an ape.
• 3 Pan troglodytes sub-species: 1. Pan troglodytes schweinfurthii (Eastern Common Chimpanzee). 2. Pan troglodytes troglodytes (Central Common Chimp). 3. Pan troglodytes verus (Western Common Chimp).
  • But P. t. vellerosus has been described since.
• 3 types of primates: 1. Prosimians. 2. Monkeys (old & new world). 3. Apes (lesser & greater apes, as well as humans).
  • But Old World and New World monkeys are not a natural
    group.
• 3 social group types of the great apes: 1. Orangutans (solitary - little amount of both sexes). 2. Gorillas (harems - great amount of one sex). 3. Common chimpanzees (live in territories defended by related males - great amount of both sexes).
  • But Bonobos represent a fourth type of social structure, with equal sex ratio but unique hierarchy.
• 3 traditional families of hominoids (apes) : 1. Hylobatidae - include the so-called lesser apes of Asia, the gibbons and siamangs. 2. Hominidae (great apes) - include living humans and typically fossil apes that possess a suite of characteristics such as bipedalism, reduced canine size, and increasing brain size such as the australopithecines. 3. Pongidae - include the remaining African great apes including gorillas, chimpanzees, and the Asian orangutan.
  • But Pongidae are united with the Hominidae by modern science, as they are paraphyletic otherwise.

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