Ontogenetic bases of canine dimorphism in anthropoid primates

Abstract

This study tests hypotheses regarding the ontogeny of canine tooth size dimorphism in five anthropoid primate species (Saguinus fuscicollis, Macaca mulatta, Cercocebus atys, Papio hamadryas, and Mandrillus sphinx). Canine measurements and chronological age data are analyzed to determine if bimaturism, a sex difference in the age at which eruption ceases, accounts for canine tooth sexual dimorphism. Canine height measurements are evaluated through a variety of regression techniques. Results show a lack of sexual dimorphism in Saguinus. While size dimorphism is absent in the deciduous teeth of all species analyzed, the adult teeth in cercopithecines become increasingly dimorphic through ontogeny. Female adult tooth eruption regularly precedes male tooth eruption, and regression-based eruption trajectories for both sexes intersect at about the age at which the female tooth reaches adult size. Males erupt the tooth later and more rapidly than females. Males also reach a larger adult size than females by erupting the tooth for much longer periods of time. Bimaturism is primary in the production of dimorphism, but rates of eruption show modest variation. These results point to the scheduling of sexual selection through intermale competition as a primary factor determining male eruption timing, rates of eruption, and adult size. Life history factors may play a role in determining the relations between the scheduling of intrasexual competition and canine eruption. Female contributions to sexual dimorphism are apparent in these species, suggesting that similar levels of dimorphism can be attained through diverse ontogenetic pathways.

Enamel extension rate patterns in modern human teeth: Two approaches designed to establish an integrated comparative context for fossil primates

“…Taller human teeth grow both longer and faster. These findings echo the developmental mechanisms producing the sexually dimorphic canines of some non-human anthropoid primates, for whom male-female differences in crown height are primarily achieved through differences in crown formation time, with a lesser role for differences in rates of growth (Swindler, 1985;Schwartz et al, 1999Leigh et al, 2005;Guatelli-Steinberg et al, 2009). In examining other primate taxa for which previously published data exists, we find that EDJ lengths appear to be related to initial EERs and crown formation time to varying degrees.…”

Life history in male mandrills (Mandrillus sphinx): Physical development, dominance rank, and group association

“…They became alpha at about peak mass, and the decrease in body mass matched a decrease in dominance rank. Canine height also peaked at 9-11 years (Leigh et al, 2005), when males attain adult rank, and may also attain alpha rank. Canine height decreased more rapidly than body mass as males passed their prime, because of both wear and breakage, in a close parallel of male reproductive value (Leigh et al, in preparation).…”

Linear enamel hypoplasia as an indicator of physiological stress in great apes: Reviewing the evidence in light of enamel growth variation

“…While data were based on G. gorilla, P. pygmaeus, and P. troglodytes, it seems reasonable to assume that bimaturism underlies the ontogeny of sexual dimorphism in all great ape species, as this mechanism is common to all anthropoids (including platyrrhines) studied to date (Swindler, 1985;Schwartz et al, 1999;Leigh et al, 2005;Guatelli-Steinberg et al, 2009). Thus, the chances of males and females exhibiting at least one LEH defect may be similar, especially if the stresses producing LEH are primarily seasonal.…”