The teeth of some apes are formed primarily to handle the most stressful times when food is scarce, according to new research* performed at the National Institute of Standards and Technology (NIST). The findings imply that if humanity is serious about protecting its close evolutionary cousins, the food apes eat during these tough periodsand where they find itmust be included in conservation efforts.
The interdisciplinary team, which brought together anthropologists from George Washington University (GWU) and fracture mechanics experts from NIST, has provided the first evidence that natural selection in three ape species has favored individuals whose teeth can most easily handle the "fallback foods" they choose when their preferred fare is less available. All of these apesgorillas, orangutans and chimpanzeesfavor a diet of fruit whenever possible. But when fruit disappears from their usual foraging grounds, each species responds in a different wayand has developed teeth formed to reflect the differences.
"It makes sense if you think about it," says GWU's Paul Constantino. "When resources are scarce, that's when natural selection is highly active in weeding out the less fit, so animals without the necessary equipment to get through those tough times won't pass on their genes to the next generation."
In this case, the necessary equipment is the right set of molars. The team examined ape tooth enamel and found that several aspects of molar shape and structure can be explained in terms of adapting to eat fallback foods. For instance, gorillas' second choice is leaves and tree bark, which are much tougher than fruit, while orangutans fall back to nuts and seeds, which are comparatively hard.
For these reasons, the researchers theorized that gorillas would have evolved broader back teeth than a fruit diet would require in order to chew leaves, but orangutans would have thicker enamel to handle the increased stress of crunching see
|Contact: Chad Boutin|
National Institute of Standards and Technology (NIST)