Nine teeth is all it takes to declare a new species of Great Ape

A new Nature paper announces a new species of Miocene great ape, Chororapithecus abyssinicus, and both the press and the blogosphere are having a field day with this publication. From our neck of the woods, Afarensis, P.Z. Myers and John Hawks have commented on the paper and from the press Jay Kelly, Peter Andrews, and Richard Potts. No one is fully convinced.

Before, I get into the thick of it, here is a photo of the nine teeth that Suwa et al. say belong to the new Miocene great ape.

Chororapithecus abyssinicus Teeth

These teeth are 10 million year old. And Suwa et al. say the teeth are gorilla-like. Specifically the tooth morphology at the enamel-dentine junction is like that of a gorilla, but christened a new species name to these teeth. Hawks criticizes the findings,

“Nor is it entirely obvious that Chororapithecus is actually gorilla-like in these characters. The paper compares two ratios involving cusp dimensions measured internally beneath the enamel cap. That’s high-tech, but the ratios do not sort out gorillas from chimpanzees, don’t sort Chororapithecus from either of those apes or early hominids, and — even worse — it’s not even clear how these ratios may vary with size. Does Chororapithecus look sort-of like a gorilla on these ratios because it’s a sort-of gorilla? Or because it’s big? The enamel is relatively thicker than gorillas, like other Miocene apes and orangutans. Clearly the specimen is much less derived than gorillas, but could that be because it isn’t a gorilla?

Well, there’s the problem: there’s not too much to go on with these teeth. I think Suwa et al. laid out as good a case as there is. A 10-million-year-old gorilla can’t be expected to look just like gorillas today.”

In their defense, Suwa and crew are saying the teeth belong to a member of the gorilla family stem from similarities with teeth of modern gorillas.

Others are are criticizing this conclusion because it completely goes against what the genetic evidence has been telling us. Early this year two papers reassessed the time at which hominids diverged from the other great apes, and that was about 7 million years ago. If teeth are the safe-houses of genotype to phenotye, a common understanding in evolutionary studies, the two lines must agree. With a 10 million year old gorilla like ape and a suggestion that the split happened earlier than 10 million years ago, this just screws with the genetic findings, and further complicates the relationship between paleoanthropology and molecular evolution.

Until I read the paper and I’ll leave you with what Afarensis said,

“You would have thought paleoanthropology would have learned something from Ramapithecus. Dental gorillas don’t mean actual gorillas. Just like being a dental hominid didn’t make Ramapithecus a real hominid.”

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