The evolution of human teeth is a much simpler process than we previously thought, and scientists from Monash University are using this new knowledge to predict the sizes of human teeth that are missing from human fossils and those of our extinct hominin relatives.
The study, led by evolutionary biologist Alistair Evans, examined the teeth of humans and fossils of hominins and confirmed that molars, including wisdom teeth, possess sizes that follow "the inhibitory cascade," which is a rule that predicts how teeth affect each other's sizes. The adherence of human teeth to this rule points to an evolutionary simplicity of tooth growth and opens up more potential for learning about our evolution through their examination.
"Teeth can tell us a lot about the lives of our ancestors, and how they evolved over the last seven million years," Evans said in a press release. "What makes modern humans different from our fossil relatives? Palaeontologists have worked for decades to interpret these fossils, and looked for new ways to extract more information from teeth."
"Our new study shows that the pattern is a lot simpler than we first thought - human evolution was much more limited," he added.
Evans and his team used a database of fossil hominins and modern humans spanning several decades in combination with high-resolution 3-D imaging to examine the insides of fossilized teeth. Afterwards, they took their findings and applied them to the two main groups of hominins: the species from the Homo genus, like modern humans, and the australopiths, which includes the famous Lucy specimen discovered in Africa.
The results showed that each group's molars follow the inhibitory cascade, although each process differs slightly.
"There seems to be a key difference between the two groups of hominins - perhaps one of the things that defines our genus, Homo," Evans said.
He added: "What's really exciting is that we can then use this inhibitory cascade rule to help us predict the size of missing fossil teeth. Sometimes we find only a few teeth in a fossil. With our new insight, we can reliably estimate how big the missing teeth were. The early hominin Ardipithecus is a good example - the second milk molar has never been found, but we can now predict how big it was."
In the future, the team hopes to use the results to interpret new hominin fossils and uncover some of the unknown drivers of human evolution, which will not only help us understand our past but also predict where our species is going in the future.
