Researchers at University College London have discovered that human skulls evolved at an exceptionally rapid pace compared to other apes, developing larger brains and flatter faces twice as quickly as expected. This acceleration likely stems from cognitive and social evolutionary pressures. The findings, based on 3D skull models, highlight unique human adaptations among great apes.
A new study by UCL anthropologists reveals that humans evolved their skull structures much faster than any other ape species, underscoring the intense selective forces behind our brain expansion and facial flattening. Published in Proceedings of the Royal Society B, the research analyzed 3D digital models derived from CT-scans of skulls from seven hominid species—great apes including humans, gorillas, chimpanzees, orangutans, and bonobos—and nine hylobatid species, or lesser apes like gibbons.
Hominids and hylobatids diverged from a common ancestor about 20 million years ago. While lesser apes have shown minimal skull variation since then, great apes display greater diversity, with humans exhibiting the most pronounced changes. The team divided skulls into four regions—upper face, lower face, front of the head, and back of the head—and used computer analysis to measure evolutionary rates.
Lead author Dr. Aida Gomez-Robles explained: "Of all the ape species, humans have evolved the fastest. This likely speaks to how crucial skull adaptations associated with having a big brain and small faces are for humans that they evolved at such a fast rate. These adaptations can be related to the cognitive advantages of having a big brain, but there could be social factors influencing our evolution as well."
The analysis showed human skulls changed roughly twice as much as expected under normal evolutionary rates, suggesting additional drivers beyond standard variation. Most great apes have projecting faces and smaller brains, unlike humans' rounder heads and flatter faces. Gibbons share some facial flatness but have smaller brains.
Dr. Gomez-Robles added: "After humans, gorillas have the second fastest evolutionary rate of their skulls, but their brains are relatively small compared to other great apes. In their case, it's likely that the changes were driven by social selection where larger cranial crests on the top of their skulls are associated with higher social status. It's possible that some similar, uniquely human social selection may have occurred in humans as well."
These insights suggest that while intelligence played a role, social dynamics may have also propelled human craniofacial evolution.