How gum disease and ageing may have shaped the human face
- Wits Faculty of Health Sciences
A recent study of fossilised jaws from early human relatives offers a fascinating and unexpected idea.
The study, ‘Craniofacial Evolution and Alveolar Bone Loss, ’ suggests that a common health problem, gum disease, together with the effects of ageing, may have played a role in shaping how our faces and brains evolved.
Looking at ancient teeth for clues
The researchers examined 71 fossil jaw specimens from early human ancestors found in South Africa. These included Australopithecines and early members of the Homo group, such as Homo habilis and Homo erectus.
Using advanced imaging techniques, they studied the bone that supports the teeth. This bone is often damaged in people with gum disease. By measuring how much of this bone had been lost, the team could build a picture of oral health in species that lived millions of years ago.
Professor Ugo Ripamonti, an internal medicine researcher at the Wits Faculty of Health Sciences, says they examined how old each individual was at the time of death, using tooth eruption as one indicator, among other things.
“The age status is determined by evaluation of the wear and tear of the enamel and the dentine. Below the enamel, often exposed,” he explains.
Gum Disease in Early Humans
The study found a clear pattern. Early Homo species showed more severe bone loss than Australopithecines.
However, the damage was not random. It looked very similar to modern gum disease, with deep gaps in the bone and areas where it had been eaten away between teeth. Australopithecines, by contrast, showed milder and more even bone loss.
He says meal-preparation techniques, such as cooking their food to soften it, may have altered the microbial ecosystem in their mouths, particularly targeting the oral cavity.
“There was, of course, also the evolution of more pathogenetic microorganisms causing more gum inflammation in [the] extent [observed],” he clarifies.
The effects of ageing
Ageing plays an important background role in these findings. Even today, gum disease is more common and more severe as people get older.
This means that some of the bone loss seen in fossils likely reflects the fact that individuals lived long enough for disease to develop. In other words, ageing creates the conditions that allow gum disease to progress.
He says gingival inflammation, the irritation and swelling of the gums, is often related to poor prosthetic rehabilitation, such as crowns that overhang the tooth. “This affects plaque retention and thus inflammation, plus more and more processed food impinging on the gingivae and crowns,” says Professor Ripamonti.
However, the researchers argue that ageing alone does not explain the differences they observed. Early Homo species did not just show more bone loss; they showed a different pattern, including deeper and more destructive forms of disease.
Natural selection
From these findings, the researchers suggest that gum disease, building up over time as individuals age, may have influenced human evolution.
As early humans aged, they developed gum disease, which then caused bone loss and weakened their ability to chew. Over many generations, natural selection favoured individuals with smaller teeth and less powerful chewing muscles.
“In general, animals cannot survive without teeth to masticate. A selected mutation must have happened, controlling a reduction of the masticatory dimension of the crowns,” adding that this also allowed for brain expansion and Homo status.
Wider implications
The study highlights how important oral health has always been. Gum disease remains very common today and becomes more likely with age, making it a continuing public health concern.
While the idea that gum disease shaped human evolution is still a theory, it offers a fresh and thought-provoking perspective.