Humans evolved their unique skull shape—large brains and flat faces—at a much faster rate than any other ape species, according to new research from University College London (UCL).
The findings suggest that both our intelligence and social behavior may have played key roles in speeding up our evolution.
The study, published in Proceedings of the Royal Society B: Biological Sciences, used 3D digital models to compare the skulls of modern apes, including humans, chimpanzees, gorillas, and gibbons.
By studying how skull shapes changed over millions of years, the researchers discovered that human skulls evolved at roughly twice the speed that would be expected through normal evolutionary processes.
“Of all the ape species, humans have evolved the fastest,” said lead author Dr. Aida Gomez-Robles of UCL Anthropology.
“This likely shows how important the skull adaptations for a big brain and small face were for our success as a species.”
To understand how humans differ, the team compared seven species of great apes—humans, chimpanzees, bonobos, gorillas, and others—with nine species of smaller apes known as gibbons.
Gibbons and great apes shared a common ancestor about 20 million years ago. Since then, great apes have developed much more diverse skull shapes, while gibbons’ skulls have remained remarkably similar to one another.
Using advanced computer analysis, the researchers divided each skull into four main regions: the upper face, the lower face, the front of the head, and the back of the head.
They then measured how much each part varied across different species.
The results revealed that humans have changed the most—developing rounder heads to house larger brains, as well as flatter faces compared to our ape relatives.
Most great apes today, such as chimpanzees and gorillas, have large, forward-projecting faces and smaller brains.
Humans, on the other hand, evolved flatter faces and bigger, more rounded skulls.
Interestingly, gibbons share a few traits with humans—such as relatively flat faces—but their brains remain small, showing that facial shape alone doesn’t explain the pace of human evolution.
The researchers believe that something beyond brain size may have accelerated our changes. While larger brains bring cognitive advantages like problem-solving and communication, social factors could also have influenced the shape of the human skull.
“After humans, gorillas have the second-fastest rate of skull evolution,” said Dr. Gomez-Robles. “But their brains are quite small, so their changes likely relate to social selection. For example, the large ridges on male gorilla skulls are linked to social dominance.”
Similarly, humans may have experienced their own kind of social selection—pressures related to cooperation, competition, and complex social behavior—that encouraged faster evolutionary change.
Overall, the study highlights just how unique human evolution has been. In only a few million years, our ancestors’ skulls transformed more dramatically than any other ape’s—helping shape the brains and faces that define who we are today.
