"Fossils are often maddeningly incomplete, but now those incomplete pieces can be useful, and they could answer questions about our own lineage, like how big our ancient ancestors were."ĭeutsch hopes to continue refining the existing equations and expand the work beyond primates to other mammals, including carnivores. "As long as the fossil has a bit of root you can use the formulas even if the tooth crowns are missing," Deutsch says. The formulas can also explain up to 96% of variation in body mass within the examined primate sample.īut perhaps the most useful application of the equation will be with fossils that are currently of little use to anthropologists and paleontologists. The formulas can be used to estimate body mass of primates with more or less specificity, depending upon whether their class is known.
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Ultimately, she found that the tooth roots only related to diet in a few lineages (for example, lemurs) however, she was able to determine how big the primates were across all lineages.ĭeutsch developed a series of formulas based on the relationship between the tooth root surface of a molar or premolar-the teeth located between canines and molars-and primate body mass. "It was a bit like trying to figure out if you have an ax or hammer based on the shape of the handle," Deutsch says. Using computer tomography, Deutsch analyzed and calculated the tooth root surface area-or area of contact where the root fits into the jaw-of 70 primates from 75 species, ranging in size from tiny mouse lemurs to great apes. In the same way, a big tooth root can transmit more force to the tooth's crown to crush more obdurate foods."ĭeutsch and the research team initially set out to determine whether tooth roots could indicate the shape of the tooth's crown, thus telling them what particular primates preferred to eat.
So if a hammer has a small handle, it will have a small head to hammer small things. "You can think of the root as the handle of a hammer-the handle size is related to the amount of force you can put into the hammer. "The tooth root transmits the force of the jaws into the food," says Adam Hartstone-Rose, professor of biological sciences at NC State and paper coauthor. The part that keeps the tooth anchored in the jaw is the root.
What we commonly think of when we think of teeth isn't the whole story-the part that does the chewing is merely the crown. Ashley Deutsch, NC State graduate student and first author of a paper describing the research, wanted to know if it was possible to determine what a primate's diet was without having the actual tooth crowns at hand-by looking instead at the roots.