Why do human faces stop growing in adolescence, unlike Neanderthals?

A new study has uncovered important insights into the differences in facial growth between modern humans and Neanderthals. Researchers have discovered that human faces grow more slowly and cease growing in early adolescence, while Neanderthals’ faces continued to develop into early adulthood.

“These two human species followed different developmental trajectories for their facial bones,” said Alexandra Schuh, a postdoctoral researcher at the Max Planck Institute for Evolutionary Anthropology in Germany, in an interview with Live Science.

Published on March 24 in the Journal of Human Evolution, the study analyzed the midface region of 174 skulls from Homo sapiens, Neanderthals, and chimpanzees. By examining skulls from various stages of development, the researchers focused on facial ontogeny, or how facial bones grow and develop.

To achieve this, the researchers used two advanced techniques. First, they created virtual 3D models of the skulls and digitized over 200 landmarks on the upper jawbones to identify patterns of growth and development. They then conducted a microscopic analysis to explore bone formation and resorption—a natural process in bone remodeling that helps retain bone structure and strength.

“We found that bone formation is predominant in Neanderthals—from birth on—who develop larger and more projecting faces,” Schuh explained. “In contrast, present-day humans exhibit significantly higher levels of bone resorption.”

The research found that while chimpanzees and Neanderthals had larger, faster-growing faces, modern humans developed smaller faces that stop growing sometime during adolescence.

“Earlier growth cessation is a distinctive feature of our species,” Schuh added. “We have identified a unique developmental pattern seen exclusively in Homo sapiens.”

For years, experts have speculated about why Neanderthals had such large faces and noses, with theories ranging from adaptation to a cold climate and higher energy needs to the chewing of tough foods and the use of teeth as tools. In contrast, various explanations have been proposed for humans’ smaller faces, including the advent of cooking and the increase in brain size.

However, understanding the precise reason behind the development of humans’ uniquely small faces remains a complex question. Schuh emphasized that while the study does not answer the "why" of this evolution, it offers a critical first step in addressing the "how."

"However, our study addresses aspects of the 'how,'" Schuh said, "providing an important first step toward understanding these processes."

By Vugar Khalilov