Scientists have added two species of ape and monkey to the evolutionary tree, filling in a 10-million-year gap in the fossil record from a period when apes and Old World monkeys diverged.
Fossil specimens of jaws and teeth, collected by
Rukwapithecus fleaglei was identified as a hominoid predecessor to the modern ape or chimpanzee, and Nsungwepithecus gunnelli was believed to be an early cercopithecoid, or Old World monkey, similar to a baboon or macaque.
The primates lived during the Oligocene epoch, which lasted from about 34 million to 23 million years ago, at a time when mammals began to evolve rapidly. Piecing together the narrative from the fossil record, however, has proved tricky.
"The late Oligocene is among the least sampled intervals in primate evolutionary history, and the Rukwa field area provides a first glimpse of the animals that were alive at that time from Africa south of the equator," said Ohio University paleontologist Nancy Stevens, who led the research.