Ancient gum disease reshaped jaws in early humans before brain expansion

On July 1, 2026, researchers from Wits University revealed that ancient gum disease significantly influenced the evolution of human jaws prior to the expansion of brain size. This groundbreaking study highlights how periodontal diseases may have played a crucial role in shaping the evolutionary trajectory of modern humans.

Link Between Gum Disease and Jaw Evolution

According to Professor Ugo Ripamonti, lead author of the study titled "Craniofacial Evolution and Alveolar Bone Loss: A Lesson from Hominins," published in the Journal of Craniofacial Surgery, periodontal diseases are among the oldest recognized diseases in human evolution. The research team examined 71 fossil jaws dating back between 5.3 million and 2.6 million years from collections at Wits and the Ditsong Museum of Natural History.

They found that species in the genus Homo suffered from significantly greater alveolar bone loss due to gum disease compared to their australopithecine relatives. Alveolar bone, which supports and anchors teeth in the jaws, deteriorates as a result of periodontal disease.

How Periodontal Disease Influenced Human Anatomy

Ripamonti noted, "We found that the Homo species developed significant alveolar bone loss, with distinctive crater-like lesions and defects around the teeth that were largely absent in australopithecines." This loss of bone structure potentially allowed for changes in facial anatomy, which may have contributed to the evolution of modern humans.

The researchers propose that chronic gum disease initiated a chain reaction that reduced the size of facial muscles and teeth. This reduction enabled the brain cavity to expand, facilitating significant brain growth over millions of years.

Challenging Traditional Evolutionary Narratives

This study presents a challenge to the traditional "survival of the fittest" narrative by illustrating how a common illness can shape the physical characteristics of a species. It bridges the fields of dentistry, bone biology, and anthropology, potentially answering why human jaws shrank while brains grew. The findings suggest that as chewing demands decreased, the need for large facial muscles diminished, leading to a less protruding face.

• Periodontal disease linked to jaw evolution
• Study examined 71 fossil jaws
• Significant alveolar bone loss in Homo species
• Chronic disease may have allowed for brain expansion

As a result, the research suggests that over millions of years, a less protruding face may have created space for the rapid brain growth that characterizes modern humanity.