Related Experiment Video
Updated: Feb 14, 2026

Rapid Isolation of Wild Nematodes by Baermann Funnel
Published on: January 31, 2022
Natural selection on molar size in a wild population of howler monkeys (Alouatta palliata)
David DeGusta1, Melanie A Everett, Katharine Milton
1Museum of Vertebrate Zoology, and Department of Integrative Biology, University of California, Berkeley, CA 94720-3160, USA. degusta@uclink.berkley.edu
Abstract:
Dental traits have long been assumed to be under selection in mammals, based on the macroevolutionary correlation between dental morphology and feeding behaviour. However, natural selection acting on dental morphology has rarely, if ever, been documented in wild populations. We investigated the possibility of microevolutionary selection on dental traits by measuring molar breadth in a sample of Alouatta palliata (mantled howler monkey) crania from Barro Colorado Island (BCI), Panama. The age at death of the monkeys is an indicator of their fitness, since they were all found dead of natural causes. Howlers with small molars have significantly decreased fitness as they die, on average, at an earlier age (well before sexual maturity) than those with larger molars. This documents the existence of phenotypic viability selection on molar tooth size in the BCI howlers, regardless of causality or heritability. The selection is further shown to occur during the weaning phase of A. palliata life history, establishing a link between this period of increased mortality and selection on a specific morphological feature. These results provide initial empirical support for the long-held assumption that primate molar size is under natural selection.
Related Concept Videos
Limits to Natural Selection
What is Natural Selection?
Natural Selection and Adaptation
Beyond physical adaptations,...
Molar Mass
Natural Selection and Mating Preferences
Females, due to their biological roles in conception, pregnancy, and nursing,...
Conservation of Small Populations

