Chewing on the Evolution of Tooth Enamel
A trip to the dentist usually reminds us that we should brush more often, eat less candy and get one of those handy suction tubes for cleaning the fish tank. Turns out it should also remind us of another reason why we’re at the top of the Hominidae ladder – our thick tooth enamel.
Teeth are the most common fossils found and their size, growth bands and layers of enamel can tell much about the individual they came from, the species it belonged to and the times it lived in.
The Journal of Human Evolution reports that a team of geneticists and evolutionary anthropologists at Duke University played evolutionary dentist by looking at four genes (enamelysin, amelogenin, ameloblastin and enamelin) known to play a role in the development of tooth enamel. They then isolated the genes in six species: humans, gorillas, chimpanzees, orangutans, gibbons and rhesus macaques. On the enamel scale, vegetarian gorillas and chimps have the thinnest tooth coverage while humans have the thickest.
They looked for trends where the genes changed between species and where the speed of change accelerated. This indicates that the gene is in “positive selection,” meaning an evolutionary shift is occurring at a rate that will probably give the species an advantage over others. The results showed positive selection in humans in enamelysin or MMP20 and enamelin or ENAM.
It doesn’t sound like much but this is jump-up-and-down exciting news for geneticists and anthropologists like New York University professor of biomaterials and biomimetics Timothy Bromage.
This study provides the important bridges between morphology, developmental processes, and their underlying genetic regulating mechanisms. Already the results of the reported work are whittling away the many layers of regulation and evolution of enamel structure.
I’m sure when I tell this to my dentist, he’ll point out that I still haven’t evolved the the gene for flossing.