The effect of differences in methodology among some recent applications of shearing quotients.
Abstract
A shearing quotient (SQ) is a way of quantitatively representing the Phase I shearing
edges on a molar tooth. Ordinary or phylogenetic least squares regression is fit to
data on log molar length (independent variable) and log sum of measured shearing crests
(dependent variable). The derived linear equation is used to generate an 'expected'
shearing crest length from molar length of included individuals or taxa. Following
conversion of all variables to real space, the expected value is subtracted from the
observed value for each individual or taxon. The result is then divided by the expected
value and multiplied by 100. SQs have long been the metric of choice for assessing
dietary adaptations in fossil primates. Not all studies using SQ have used the same
tooth position or crests, nor have all computed regression equations using the same
approach. Here we focus on re-analyzing the data of one recent study to investigate
the magnitude of effects of variation in 1) shearing crest inclusion, and 2) details
of the regression setup. We assess the significance of these effects by the degree
to which they improve or degrade the association between computed SQs and diet categories.
Though altering regression parameters for SQ calculation has a visible effect on plots,
numerous iterations of statistical analyses vary surprisingly little in the success
of the resulting variables for assigning taxa to dietary preference. This is promising
for the comparability of patterns (if not casewise values) in SQ between studies.
We suggest that differences in apparent dietary fidelity of recent studies are attributable
principally to tooth position examined.
Type
Journal articleSubject
PGLSPlatyrrhini
Strepsirrhini
adaptation
dietary ecology
discriminant function analysis
mastication
structural carbohydrate
Animals
Anthropology, Physical
Discriminant Analysis
Least-Squares Analysis
Mastication
Molar
Primates
Permalink
https://hdl.handle.net/10161/9221Published Version (Please cite this version)
10.1002/ajpa.22619Publication Info
Boyer, Doug M; Winchester, Julia; & Kay, Richard F (2015). The effect of differences in methodology among some recent applications of shearing
quotients. Am J Phys Anthropol, 156(1). pp. 166-178. 10.1002/ajpa.22619. Retrieved from https://hdl.handle.net/10161/9221.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
Collections
More Info
Show full item recordScholars@Duke
Douglas Martin Boyer
Associate Professor of Evolutionary Anthropology
Richard Frederick Kay
Professor of Evolutionary Anthropology
I have two areas of research:1) the evolution of primates in South America; and 2)
the use of primate anatomy to reconstruct the phylogenetic history and adapations
of living and extinct primates, especially Anthropoidea. 1) Evolution of primates
and mammalian faunal evolution, especially in South America. For the past 30 years,
I have been engaged in research in Argentina, Bolivia The Dominican Republic, Peru,
and Colombia with three objectives:a) to reconstruct the evol
Alphabetical list of authors with Scholars@Duke profiles.

Articles written by Duke faculty are made available through the campus open access policy. For more information see: Duke Open Access Policy
Rights for Collection: Scholarly Articles
Works are deposited here by their authors, and represent their research and opinions, not that of Duke University. Some materials and descriptions may include offensive content. More info