A baby ape discovered in Kenya could be an example of the earliest ancestors  of all living humans, scientists believe.

The little creature, whose skull is roughly the size of a lemon, lived around 13 million years ago and came from a family which may have eventually evolved into man and apes .

It was discovered by Kenyan fossil hunter John Ekusi in ancient rock layers in the Napudet area, west of Lake Turkana, in the north of the country.

The fossil survived because a nearby volcano buried the forest in which it lived millions of years ago, perfectly preserving the skull, even down to the tiny ear canals deep inside its cranium.

All humans and apes alive today come from a common lineage, but until now paleontologists have only managed to trace that line back to 10 million years ago so it was unclear what our ancestors looked liked further back, and if they originated in Africa or elsewhere.

The new specimen has been labelled Nyanzapithecus alesi, with its species name taken from the Turkana word for ancestor – ‘ales.’ It was just 16 months old when it died.

A handful of bones and teeth had previously been found from the Nyanzapithecus species but scientists were unsure what the creature would have looked like, or how far back it went.

The new skull has a noticeably small snout,  like a gibbon, but scans of the inside of the cranium reveal that it had ear tubes which are closer to chimpanzees and humans.

“Gibbons are well known for their fast and acrobatic behavior in trees,” said Fred Spoor, Professor of Evolutionary Anatomy at University College London.

“But the inner ears of Alesi show that it would have had a much more cautious way of moving around.”

The find is the most complete extinct ape skull known in the fossil record. Humans themselves diverged from apes around six million years later, sharing a last common ancestor with chimpanzees about 7 million years ago.

“Nyanzapithecus alesi was part of a group of primates that existed in Africa for over 10 million years,” added lead author Dr Isaiah Nengo, of Stony Brook University.

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.”

Co-author Craig Feibel, Professor of Geology and Anthropology at of Rutgers University, New Brunswick, added: “The Napudet locality offers us a rare glimpse of an African landscape 13 million years ago.

Baby monkey that died 13 million years ago is the oldest human ancestor ever found, scientists say 04:14

“A nearby volcano buried the forest where the baby ape lived, preserving the fossil and countless trees. It also provided us with the critical volcanic minerals by which we were able to date the fossil.”

The research was published in the journal Nature .