Expression of fluctuating asymmetry in primate teeth: Analyzing the role of growth duration

This dissertation furthers our understanding of the association between growth duration and developmental noise (DN) by examining fluctuating asymmetry (FA) in a non-sexually selected and a sexually selected structure. FA occurs as small, random deviations from bilateral symmetry without any directionality between sides. Extended periods of growth may provide a `window of opportunity’ for growing body structures to accumulate perturbations resulting in elevated DN, manifested as FA. In comparison to other mammalian species, primates exhibit prolonged growth. Within the primate order, growth periods lengthen from prosimians to apes and humans. Although prolonged growth periods can be advantageous, lengthening of the growth period may provide the opportunity to accumulate deviations from symmetry. An association between growth duration and DN has yet to be studied across the primate order. This dissertation tested if and to what extent growth duration was associated with dental FA in primates. This potential association between growth duration and FA was first examined in the non-sexually selected first molar. First molar FA was compared between species based on crown formation times (CFTs) and life history (LH) schedules to test the hypothesis that species with prolonged CFTs or LH schedules would express greater first molar FA relative to species with shorter CFTs or LH schedules. The results generally lend support to the hypothesis; however, not all comparisons are statistically significant. An additional aim was to elucidate the mechanism(s) which underlie the association between FA and sexually selected structures. Sexually selected structures are prone to exhibiting elevated FA because they may be destabilized by directional selection. The primate canine has been given as one example of a sexually selected structure prone to expressing elevated FA. It is possible that the mechanisms believed to explain elevated canine FA in primates may not be associated with the destabilization of developmental processes but rather with the fact that males of sexually dimorphic species grow their canines for a longer period of time relative to their female counterparts. Two approaches were used in testing for an association between FA and sexual selection. First, canine FA was compared between males and females of a species. Generally, males of sexually dimorphic species expressed greater canine FA but not all comparisons were statistically significant. To further test this association, male canine FA was evaluated through linear regressions and controlled comparisons among males of different species. Linear regression results indicated that canine growth duration more closely predicted canine FA than variables representing sexual selection. Controlled comparisons that included great apes support the hypothesis that prolongation of growth is associated with elevated FA. An association between growth duration and FA is further supported in some but not all comparisons between males of different monkey species. Because anthropologists, and other scholars, use FA as an indicator of developmental stress, understanding what factors are associated with FA is essential to accurately intrepreting FA data. The results of this dissertation lend support to the hypothesis that growth duration contributes to dental FA in both a non-sexually selected and a sexually selected structure.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Anthropology

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Martin, Sarah Abigail

Contributors dc:contributor

• Guatelli-Steinberg, Debbie

• Animals
• Physical Anthropology
• Developmental Biology
• Museum Studies
• fluctuating asymmetry
• growth and development
• dental anthropology
• primates
• life history
• weaning

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1366187797

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1366187797