Looking at teeth in a new light
- Center for Functional Anatomy and Evolution, The Johns Hopkins University School of Medicine, 1830 East Monument Street, Baltimore, MD 21205
Teeth are the most common elements in the mammalian fossil record. Thus it is not surprising that they have yielded many insights into the lives of extinct creatures. When researchers in the 1970s noted that subtle differences in molar tooth shape could be correlated with significant dietary differences (1–7), it opened the door for a vast array of “functional analyses” of teeth in which various measurements of tooth shape were statistically compared between modern and prehistoric species (8–11). Yet there was one underlying limitation to all of that work: it was ultimately based on landmark-based, point-to-point measurements of unworn teeth. Because teeth begin to wear down as soon as they are used, most fossil teeth were unavailable for functional analyses. In essence, as wear progressed, the reference points for the measurements in question changed dramatically, making accurate measurements difficult, if not impossible (Fig. 1). This issue of PNAS contains a report by Ungar and M'Kirera (12) that changes that in dramatic fashion, bringing tooth measurements into the 21st century.
Nine years of wear on a mandibular molar from a Costa Rican howling monkey (Alouatta palliata). (Left) Baseline, July 1989. (Right) Follow-up, July …
