Researchers looked at how evolution shape human tooth enamel over time.
Researchers compared the human genome with that of five other primates to see how we got our characteristic thick enamel, a Duke University news release reported.
Enamel is a strong indicator of diet; vegetarian species tend to have thinner enamel than those that eat meat.
"Teeth also preserve their growth bands," author Christine Wall, associate research professor of evolutionary anthropology at Duke said in the news release. "So in terms of understanding fossils, teeth can tell you how old a juvenile was when it died, or how long it takes for teeth to develop -- so you can compare between living and extinct species."
The team looked for genetic changes that would have led to humans' extra thick enamel.
"We decided to look just at genes that have a known role in tooth development," said Greg Wray, professor of biology at Duke said in the news release.
The team looked at four genes that had codes for a protein involved in tooth formation. These included "enamelysin, amelogenin, ameloblastin and enamelin," the news release reported.
The researchers sequenced the genes and fed the information into a computer software program that looked at how base pairs changed between species.
"That's when we know a gene is under positive selection," first author Julie Horvath, director of the genomics and microbiology lab at the Nature Research Center in Raleigh, NC and research associate professor of biology at North Carolina Central University said in the news release.
The team used the idea of genetic drift to come to their conclusion. Drift occurs when changes in the DNA sequence accumulate at an accelerated rate; the phenomenon suggests the genes are under positive selection, giving them an advantage. The team found positive selection in genes affecting enamel thickness in humans.
"This study provides the important bridges between morphology, developmental processes, and their underlying genetic regulating mechanisms," Timothy Bromage, professor of biomaterials and biomimetics at New York University, who was not involved with the study said in the news release. "Already the results of the reported work are whittling away the many layers of regulation and evolution of enamel structure."
