The infant ape’s life was brief, running out before the age of 2. Yet its discovery 13 million years later by a team led by Bay Area anthropologist Isaiah Nengo is casting light on a shadowy and pivotal period in prehuman history.
Characteristics of the fossil, the most complete extinct ape skull ever found, mark it as a new species in the great flowering of ape evolution, which later led to the emergence of humans. We didn’t descend from the little ape; rather, we have kin in common.
“Together, we have great-great-great-great grandparents that we all share,” said Nengo, who lives in Ross, digs in Kenya and teaches at Cupertino’s De Anza College. His research, published in Wednesday’s issue of the prestigious journal Nature, was funded by the San Francisco-based Leakey Foundation, founded to explore the origins of humanity.
Little is known about ancient apes, the ancestors of living apes and humans.
It was a time of great evolutionary success, with an explosion of genetic diversity. And then the apes mysteriously declined. Only a few remained, in restricted places: gibbons and orangutans in Asia and chimps, gorillas and the early human australopithecines in Africa.
In contrast, monkeys prevailed. And humans, for better or worse, are extraordinarily successful.
The 13-million-year-old fossil, now extinct, reveals what the common ancestor of all living apes and humans may have looked like. Dating back to the Miocene, its species has been named Nyanzapithecus alesi.
We branched off quite recently, only 6 to 7 million years ago.
The stunning discovery in 2014 came at the end of a long and disappointing day near the western shore of Kenya’s Lake Turkana in Africa’s Great Rift Valley, in a place full of volcanic rock and largely devoid of fossils, said Nengo.
Nengo was deeply invested in the success of the project at the Turkana Basin Institute. He had secured grant funding, assembled the team, coordinated the effort and was responsible for everything from fuel in trucks to water in jugs.
“We spent the whole day finding nothing. Zero. We were in a pretty bad mood,” he recalled. So the team gave up and went back to camp for dinner, walking the familiar route they had always taken, back and forth, every day.
An assistant, John Ekusi, pulled out a cigarette. “We told him: ‘You’re going to kill us! Smoke it far away,’ ” Nengo said. So Ekusi walked ahead of the team, about 500 yards.
Then Ekusi suddenly stopped, looking down, intently. He spotted something in the rock — the leg bone of an elephant, perhaps?
“We rushed to where he was, yelling ‘What did you find?’ and we knew right away it was super special,” said Nengo. Taking out a brush, he whisked away dirt. “We instantly knew it was a cranium, with an eye socket in front. It was extremely well preserved.”
Anthropology is a profession that usually works with mere fragments. “It was incredibly shocking,” he said.
But they were running out of daylight. So the team re-buried the fossil, returned to camp and waited for the sun to rise. “It was a terrible night,” he laughed.
Starting at 5 a.m. the next day, they excavated a block of rock around the fossil, then drove it back to a larger supply campsite, where it could be safely transported to a lab. (Its name is taken from an African word for ancestor “ales.” Fondly, Nengo’s team calls it “Alesi.”)