Ancient teeth, larger than current ones, are, when well preserved, particularly valuable for archaeologists. They reveal key stages of human evolution, such as the adoption of cooked food. However, researchers still have little information on the genetic mechanisms responsible for differences in tooth size and shape within current human populations.
A new study, published in the journal Current Biology on December 12, 2024 and spotted by ScienceAlert, identified eighteen regions of the genome influencing these characteristics, seventeen of which had never before been linked to our jaws. One of these variants, the HS3ST3A1 gene, may even have been inherited from Neanderthals (Homo neanderthalensis) – just like those coding the shape of the nose or even the tendency to be a “morning” person.
A day in Macondo, northeastern Colombia
Genetics and diversity of dental dimensions
For the purposes of the research, the international team crossed the data of 882 Colombian volunteers selected for their genetic diversity resulting from their mixed origins (European, Native American and African). She focused in particular on the dimensions of the mesiodistal diameter (width of the tooth), the buccolingual diameter (thickness of the tooth) and the crowns (visible parts of the tooth, which protrude from the gum) of their teeth, obtained thanks to to 3D scans of plaster dental casts.
These measurements were compared with the genetic profiles of the participants, using a genome-wide association study (GWAS, for Genome-Wide Association Study), a method that can identify specific regions of the genome associated with particular traits – randomly, the size or shape of teeth. Finally, scientists also studied, in mice, the effect of key genes on their dental development, by activating or deactivating them.
The results therefore made it possible to discover eighteen new regions of the genome influencing the size and shape of teeth. They also highlight how these genetic variations affect dental dimensions depending on different ethnic groups.
For example, among these new associations, one concerns a gene supposedly inherited from Neanderthals, following crosses with ancient members of our species (A wise man). However, this genetic variant has only been identified in people of European origin, who generally had smaller teeth.
Furthermore, if the EDAR gene was already known to influence the shape of incisors in East Asian populations, the recently published study reveals that it also plays a role in determining the width of all teeth , especially among Native Americans.
Advances towards precision medicine
Specialists have not been able to prove that these variations were selected during evolution to improve dental health. “It is therefore possible [qu’elles l’aient été] due to the influences they exert in other areas, the differences in tooth shape being only a secondary effect”indicates in a press release Andrés Ruiz-Linares, professor of human genetics in the Department of Genetics, Evolution and Environment at London’s Global University and co-senior author of the study.
Scientists are just beginning to explore teeth using so-called “omics” technologies, which allow us to explore different levels of biological functioning (DNA, RNA, proteins, molecules) to obtain an overview. Here, they enable the analysis of vast amounts of biological data, including not only genetic variations, but also gene regulation, activation and protein production.
In addition to tracing the evolution of teeth over millennia, research like this could help identify the causes of various dental health problems – many of which are linked to genes – and develop treatments.
“We hope that our results can be useful medically, if people with particular dental problems can undergo genetic testing to help with diagnosis, or if certain dental abnormalities can one day be treated with gene therapies.”concludes Dr Qing Li from Fudan University (China), first author of the study.
