Why do many people consider bonobos to not be chimpanzees, but nobody consider eastern gorillas to not be gorillas?
When I was growing up (ages ago), there were thought to be four living species of great ape (not counting humans):
- Common chimpanzees (Pan troglodytes)
- Pygmy chimpanzees or bonobos (Pan paniscus)
- Gorillas (Gorilla gorilla)
- Orangutans (Pongo pygmaeus)
Since then there have been some developments:
- Eastern gorillas (Gorilla beringei) were recognized as a separate species from western gorillas (Gorilla gorilla), instead of a subspecies.
- Sumatran orangutans (Pongo abelii) were recognized as a separate species from Bornean orangutans (Pongo pygmaeus), instead of a subspecies.
- Tapanuli orangutans (Pongo tapanuliensis) were discovered to be a separate species.
Notably, nothing changed about the taxonomic status of chimpanzees (Pan). And yet I feel there has been a change in the vernacular terms for them. "Pygmy chimpanzee" has dropped entirely from usage in favor of "bonobo", which make sense, since they're barely any smaller. But also I notice more people using "chimpanzee" to just refer to Pan troglodytes.
This feels like a bad move to me, because it leaves Pan without a vernacular term. It also seems inconsistent -- why wouldn't we also restrict "gorilla" to Gorilla gorilla and "orangutan" to Pongo pygmaeus, with new names for the other species (say, "ingagi" for Gorilla beringei, "mawas" for Pongo abelii, etc.)?
What do people think?