Fossil ape skull confirms African origin of apes and humans

13-million-year-old “Alesi“, a fossil discovered in Kenya, sheds light on ape ancestry

August 09, 2017

The discovery in Kenya of a remarkably complete fossil ape skull reveals what the common ancestor of all living apes and humans may have looked like. The find belongs to an infant which lived about 13 million years ago. The research was done by an international team led by Isaiah Nengo of Stony Brook University-affiliated Turkana Basin Institute and De Anza College, USA. Senior author Fred Spoor of UCL in the UK and of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, was part of the research team.


Humans are most closely related to living ape species, including chimpanzees, gorillas, orangutans and gibbons. Our common ancestor with chimpanzees lived in Africa six to seven million years ago, and many spectacular fossil finds have revealed how humans evolved since then. In contrast, little is known about the evolution of the common ancestors of living apes and humans before ten million years ago. Relevant fossils are scarce, consisting mostly of isolated teeth and partial jaw bones. It has therefore been difficult to find answers to two fundamental questions: did the common ancestor of living apes and humans originate in Africa, and what did these early ancestors look like?

Fossil from the Miocene


The fossil is the skull of an infant, and it is the most complete extinct ape skull known in the fossil record. Many of the most informative parts are preserved inside the fossil, and to make these visible the team used an extremely sensitive form of 3D X-ray imaging at the synchrotron facility in Grenoble, France. “We were able to reveal the brain cavity, the inner ears and the unerupted adult teeth with their daily record of growth lines” says Paul Tafforeau of the European Synchrotron Radiation Facility. “The quality of our images was so good that we could establish from the teeth that the infant was about one year and four months old when it died.”

Cyprian Nyete (left) and Isaiah Nengo (right) excavating Alesi, using fine picks and brushes, as well as a hardener to protect the fossil bone.

A new species


Alesi’s skull is about the size of a lemon, and with its notably small snout it looks most like a baby gibbon. “This gives the initial impression that it is an extinct gibbon,” observes Chris Gilbert of Hunter College, New York. “However, our analyses show that this appearance is not exclusively found in gibbons, and evolved multiple times among extinct apes, monkeys, and their relatives.” That the new species was certainly not gibbon-like in the way it behaved could be shown from the balance organ inside the inner ears. “Gibbons are well known for their fast and acrobatic behaviour in trees,” says Fred Spoor, “but the inner ears of Alesi show that it would have had a much more cautious way of moving around.”


“Nyanzapithecus alesi was part of a group of primates that existed in Africa for over ten million years”, concludes lead author Isaiah Nengo. “What the discovery of Alesi shows is that this group was close to the origin of living apes and humans, and that this origin was African”.


The Leakey Foundation, SJ/HR

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