What the Last Common Ancestor of Humans and Apes Looked Like is Revealed by a Fossil

According to a recent study, the most complete ancient ape skull ever discovered provides insight into what the last common ancestor of all living apes and humans may have looked like.

The 13-million-year-old baby skull, dubbed “Alesi” by its finders, was found in Kenya in 2014. It most likely belonged to a slow-climbing, fruit-eating ape that resembled a young gibbon, according to the researchers.

Humans are the living primates that are most closely related to apes, which include great apes and lesser apes (gibbons) (chimpanzees, gorillas, and orangutans). These so-called hominoids, which include humans, gibbons, and great apes, first appeared and underwent significant evolutionary change between 23 and 5 million years ago. (Humans and chimpanzees shared a last common ancestor approximately 6–7 million years ago.)’

The ancestors of extant apes and humans from the crucial period when these branches separated are still mostly unknown. This branch of the monkey family tree has very little fossil material, which largely consists of fractured jaw fragments and single teeth. Because of this, scientists were unsure of the appearance of the final common ancestor of living apes and humans, as well as whether they came from Africa or Eurasia. Alesi and the Kenyan excavation site are seen in photos.

According to research co-author and paleoanthropologist Christopher Gilbert of Hunter College in New York, “the live apes are located all across Africa and Asia — chimps and gorillas in Africa, orangutans, and gibbons in Asia — and there are many fossil apes found on both continents, as well as Europe.” So, as you might expect, there are many potential explanations for how that distribution developed, and various academics have offered a variety of hypotheses regarding the location of the progenitor of contemporary apes and humans.


The skull was found in 2014 by Kenyan fossil hunter John Ekusi in the Napudet region, west of Lake Turkana. Because “ales” means “ancestor” in the native Turkana language, he proposed the nickname “Alesi” for the animal.

According to research co-author Craig Feibel, chair of the anthropology department at Rutgers University in New Jersey, “The Napudet location offers us a rare picture of an African environment 13 million years ago.” “The infant ape lived in a forest that was buried by a neighboring volcano, which preserved the fossil and innumerable trees. Additionally, it gave us the essential volcanic materials needed to date the fossil.

This is the oldest and most complete ape skull discovered between 7 million and 17 million years ago, dating from between 10 million and 14 million years ago.

Ellen Miller, a primatologist and paleoanthropologist at Wake Forest University in Winston-Salem, North Carolina, who is a study co-author, told Live Science that Alesi “came from exactly the right time and place to show us what the ancestors of all the modern apes and humans might have looked like.” “We never knew anything about that before; it was a mystery.”

It’s still unclear how Alesi passed away. The researchers hypothesized that perhaps the newborn was killed by the heavy layers of ash from massive volcanic eruptions that covered the fossil.



The baby tooth’s roots were still visible in the lemon-sized skull, while the adult teeth had not yet broken through the jawbone. These adult teeth’s three-dimensional X-ray scans allowed researchers to count the enamel layers that had built up over time like rings inside a tree, allowing them to determine that the infant primate was 16 months old when it passed away.
We can infer from the teeth that it typically ate fruits, according to Miller.

Alesi belonged to a genus, or group of species, known as Nyanzapithecus, a sister group to the hominoids that was discovered around 30 years ago based on the morphology of the adult teeth that had not yet erupted. Alesi belonged to a new species called Nyanzipithecus Alesi, according to the scientists, because Alesi’s teeth were substantially larger than those of other individuals in this genus. (“Nyanza” is the name of the western Kenyan province where the first Nyanzapithecus specimen was discovered; “pieces” is the Greek word for “ape”).

Nyanzapithecus Alesi belonged to a species of monkeys that have been present in Africa for over 10 million years, according to main study author Isaiah Nengo of Stony Brook University in New York. The discovery of Alesi demonstrates that this population lived quite near to the African origin of extant apes and humans.

Scientists must know that the last shared ancestors of living apes and humans originated in Africa because it advances their understanding of how ancient temperature, ecology, geography, and other elements played a crucial role in their evolution. Gilbert remarked, “It aids in understanding and reconstructing how and why a particular lineage may have evolved.

Because Alesi was too young for the features of the skull that separate the sexes to have developed, the researchers are unable to determine whether Alesi was male or female. Alesi would have matured at roughly the weight of 24.9 lbs (11.3 kg) if it had reached adulthood, according to the size of the skull and teeth. Alesi’s 6.16 cubic inch (101 cubic centimeter) brain was around the same size as a contemporary lemur of the same size, the researchers added.

Alesi’s little skull’s snout would have given her the appearance of a young gibbon. “The specimen may help give us some sort of idea of what the common ancestor of all living apes and modern humans might have looked like, and because our specimen looks most similar to gibbons among living apes, it would potentially support the idea that the common ancestor of living apes and humans looked like a gibbon,” Gilbert said. “Because they are probably close to the ancestor of all living apes, the specimen may help give us some sort of idea of

Alesi’s inner ear, which houses the primates’ balancing organ, is shaped in a way that makes her appear as though she was unable to perform the quick, acrobatic tree-swinging that gibbons are known for.

Miller assumed that the animal’s mode of locomotion was slower and more chimpanzee-like.

In the journal Nature’s August 10 issue, the researchers described their findings in full.

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