Study suggests gum disease may have helped shape human evolution

A recently published study is challenging the traditional “survival of the fittest” narrative by suggesting that a common disease such as periodontitis may have interacted with genetic changes to help shape the physical characteristics of early humans.

Researchers at Wits University in South Africa examined 71 fossil jaws dating from between 5.3 million and 2.6 million years ago from collections housed at Wits University and the Ditsong Museum of Natural History. Their findings were published in the Journal of Craniofacial Surgery in a paper titled Craniofacial Evolution and Alveolar Bone Loss: A Lesson from Hominins.

“Periodontal diseases are among the oldest recognized diseases in human evolution,” said Professor Ugo Ripamonti, from the Department of Internal Medicine, School of Clinical Medicine, and lead author of the study.

“The fossil record allows us to investigate not only when these diseases emerged, but also how they may have influenced the evolutionary trajectory of our species.”

The team found that species in the genus Homo experienced significantly greater alveolar bone loss associated with periodontal disease than their Australopithecine relatives.

Alveolar bone supports and anchors the teeth in the jaw, and its deterioration is a hallmark of periodontal disease.

“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,” said Ripamonti.

Possible link between gum disease and human evolution

The findings point to a possible link between alveolar bone loss in the genus Homo and the evolutionary changes that gave rise to modern humans.

“We typically view disease as purely destructive,” said Ripamonti. “But in this case, periodontal disease may have interacted with other biological changes in ways that contributed to the emergence of human form.”

To explain this hypothesis, the researchers looked at the skulls of pre-human ancestors, which had large, powerful jaws, thick chewing muscles and large teeth adapted for crushing tough foods such as edible roots.

While this anatomy enabled them to process tough vegetation, it also created a compact facial structure around the cranial cavity that may have limited expansion of the braincase.

The researchers propose that chronic periodontal disease, accompanied by substantial alveolar bone loss, may have triggered a domino effect that altered facial anatomy.

According to the study, a genetic mutation first resulted in smaller tooth crowns. As chewing demands declined, the large muscles used for mastication also became smaller. These changes reduced chewing forces while maintaining the ability to process food. The researchers suggest this may have contributed to reduced prognathism—the forward projection of the jaw and face seen in many earlier hominins.

Over millions of years, a less protruding face may have created additional space for expansion of the cranial vault, potentially paving the way for the rapid brain growth that characterizes modern humans.