They [wisdom teeth] do not cut through the gums till about the seventeenth year, and I am assured by dentists that they are much more liable to decay, and are earlier lost, than the other teeth.
In 1871, in the “Descent of Man,” Charles Darwin speculated that human third molars, or “wisdom teeth,” were evolving into rudimentary structures (115). Such structures, he explained, tend to be highly variable and reduced in size or even “wholly suppressed.” Wisdom teeth fit this definition well in that they show great variability in size, shape, and development. Furthermore, although the congenital absence of third molars is extremely rare in great apes (456), it is quite common in humans, with a worldwide frequency (at least one missing third molar) of 22.63% according to a new meta-analysis (260).
The reduction or absence of third molars can be viewed as part of the larger trend of dental reduction in recent human evolution, one of several aspects of modern human biology that the study of ancient teeth illuminates. Dental studies also give us insight into the phylogenetic origins and patterns of dispersal of anatomically modern humans (AMHS) out of Africa, our long developmental periods, and the evolutionary history of our dental diseases. In detailing these insights, I develop two main themes. The first is that some of these aspects of modern human biology are interrelated. As one example, our present long lifespans may give us a reproductive payoff in offspring number and/or offspring survival, but longer lifespans require teeth to function for longer periods of time, increasing the risk of dental disease.
The second theme is the dynamic relationship between culture and biology in the evolution of modern human dental reduction and dental disease, both of which have been influenced by changes in diet, food processing, and eating habits. Nevertheless, much remains to be understood about the extent to which differences among cultures over time and space can be linked to population patterns of dental reduction and dental pathology. In Chapter 7, I discussed the case of dental reduction in the Sima de los Huesos Homo heidelbergensis hominins, which José Bermúdez de Castro's analysis suggests has more to do with genetic drift than with culturally-induced relaxed selection on tooth size.