Analysis of Kamoyapithecus hamiltoni canine teeth fragments reveals that the ancient species was highly sexually dimorphic.© AMNH
New research led by a Museum paleoanthropologist and published in the Journal of Human Evolution describes ape teeth that are the oldest such fossils on record from Kenya and, possibly, worldwide.
The new study, led by Ashley Hammond, an assistant curator in the Museum’s Division of Anthropology, and colleagues from the George Washington University and Arizona State University, looked at dental fossils that were previously recovered at the fossil site Losodok, in the Turkana Basin of Kenya. The site, which has been explored by paleontology teams for the last 70 years, is famous for being the discovery place of Kamoyapithecus hamiltoni. This species, known only by its teeth and jaws, was until now, only suspected to be an ape.
“We have had very limited fossil evidence for apes earlier than about 20 million years ago, and the Kamoyapithecus hamiltoni fossils were so fragmentary that paleoanthropologists could not be sure that this species was truly an ape,” says Hammond. “Our study shows that Kamoyapithecus had dental anatomy that links it to a well-known ape genus called Proconsul, finally confirming that Kamoyapithecus is an ape.”
The analysis conducted by Hammond and colleagues of the Kamoyapithecus hamiltoni teeth specimens show that the species was highly sexually dimorphic based on canine size—males were much larger than females.
In addition, the scientists also examined a mysterious fossil canine that was assumed to come from Losodok but lacked any historical data. The researchers used X-ray fluorescence spectroscopy to uncover the geochemical makeup of the fossil material. The geochemical “fingerprint” of the canine was a match for Losodok, but further analysis found that this canine is too small to be associated with Kamoyapithecus, meaning there were likely two species of apes living in this area during this time.
“The discovery of a second ape species at this site, which could be the earliest paleontological site known for apes, is really intriguing. It means that there was already quite a bit of diversity in apes living together in a single habitat, and that this diversity in apes appeared very early on during ape evolution,” says Hammond.