But the fossil record is scarce prior to 10 million years ago, making it hard for experts to determine the link between apes and humans.
"We have a handsome ape cranium (skull) from a period that we knew virtually nothing about, and this is one of those wonderful cases where discovery leads to all sorts of new and interesting perspectives", says Craig Feibel, a professor of geology and anthropology at Rutgers University.
This does not mean the direct ancestor of living apes necessarily looked like a gibbon, just that a member of its family did at the time.
Scientists described the creature, found in Kenya, as being like a non-acrobatic baby gibbon, with a tiny mouth and nose relative to its head size. The research was done by an worldwide team led by Isaiah Nengo of the Stony Brook University-affiliated Turkana Basin Institute, Stony Brook University, and De Anza College, U.S.A.
Among living primates, humans are most closely related to apes, including chimpanzees, gorillas, orangutans, and gibbons. Our common ancestor with chimpanzees lived in Africa 6 to 7 million years ago, and many spectacular fossil finds have revealed how humans evolved since then.
And while there's debate about whether our ape ancestors came from Eurasia or Africa, this particular discovery points towards an African origin.
Now these questions can be more fully addressed because the newly discovered ape fossil, nicknamed Alesi by its discoverers, and known by its museum number KNM-NP 59050, comes from a critical time period in the African past. Alesi really sits at the origin of modern apes, so we've had a very good record of fossil humans for a long time. Numerous most informative parts of the skull 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", said Paul Tafforeau from the European Synchrotron Radiation Facility. They also said that several aspects of the new species link it to living apes.More news: Pinoys in Guam worry about NoKor's threat
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That group, which has no official name yet, lived and died millions of years ago.
"Alesi is the one that has allowed us to. know who is in that group. and when we take a close look we see that most of the group are found in Africa".
Alesi, the skull of the new extinct ape species Nyanzapithecus alesi. That's pretty much it. Paleontologists have yet to find a complete ape skull in Africa between 17 and 7 million years ago, and no skulls whatsoever between 14 and 10 million years ago.
While its baby teeth had been knocked out, Alesi's adult teeth lay unerupted inside its jaw, and their age could be determined with great precision - the ape was one year and four months old when it died.
They named it Nyanzapithecus alesi after "ales" - the word for "ancestor" in the Turkana language of Kenya, where the lemon-sized skull was unearthed. What's more, the researchers suggest that the genus to which this ape species belongs to, Nyanzapithecus, is the closest thing we know to the last common ancestor of all living apes.
The team also established that the balance organs in Alesi's ear were unlike those of the gibbon, meaning it probably had a different, slower, way of moving.
"What the discovery of Alesi shows", said lead author Isaiah Nengo, a professor of anthropology at De Anza College in California and Stony Brook University in NY, "is that this group was close to the origin of living apes and humans and that this origin was African". "I still am over the moon", said paleontologist Isaiah Nengo of New York-based Stony Brook University's Turkana Basin Institute and California's De Anza College.