The common ancestor that humans share with chimpanzees, our closest primate relatives, is believed to have walked in Africa between 6 and 7 million years ago.
Little, however, is known about the evolution of the common ancestors of humans and living apes earlier than that because of the scarcity of relevant fossils.
Now, the discovery of an ancient skull in Kenya may shed light on the origins and physical traits of these ancestors.
Most Complete Extinct Ape Skull In Fossil Record
The fossil, nicknamed Alesi, was found by a fossil hunter in 13-million-year-old rock layers. It belonged to an infant and is currently the most complete known extinct ape skull in fossil record.
Despite the skull's remarkable preservation, the researchers were not able to immediately confirm where it belonged in the primate family so they used high-powered x-rays at the European Synchrotron Radiation Facility in Grenoble, France.
The 3D imaging allowed researchers to get a glimpse of the inside of the skull without damaging the fossil and offered a wealth of information about the creature.
"The quality of our images was so good that we could establish from the teeth that the infant was about 1 year and 4 months old when it died," said Paul Tafforeau of the European Synchrotron Radiation Facility.
The scans provided the researchers with a 3D reconstruction of the teeth, which had not yet erupted. The distinctive shapes showed that the skull belonged to the Nyanzapithecus alesi, an extinct sister group to great apes, gibbons, and humans.
Prior to the discovery, the species were only known from their teeth, and there were questions whether or not they were really apes.
Alesi's lemon-sized skull has a small snout that it looked like a baby gibbon. Analyses showed that while its appearance may give an impression the creature is an extinct gibbon, researchers said that this appearance is not exclusive in gibbons and evolved several times among extinct monkeys, apes and their relatives.
Researchers said that the species belongs to a group of primates that lived in Africa for over 10 million years. The skull revealed that this group was close to the origins of living apes and humans and these are of African origin.
"The combined evidence suggests that nyanzapithecines were stem hominoids close to the origin of extant apes, and that hylobatid-like facial features evolved multiple times during catarrhine evolution," the researchers wrote in their study published in the journal Nature on Aug. 10.