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The effect of differences in methodology among some recent applications of shearing quotients.

dc.contributor.author Boyer, DM
dc.contributor.author Kay, Richard Frederick
dc.contributor.author Winchester, Julia M
dc.coverage.spatial United States
dc.date.accessioned 2014-10-31T15:58:03Z
dc.date.issued 2015-01
dc.identifier http://www.ncbi.nlm.nih.gov/pubmed/25256698
dc.identifier.uri https://hdl.handle.net/10161/9221
dc.description.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.
dc.language eng
dc.relation.ispartof Am J Phys Anthropol
dc.relation.isversionof 10.1002/ajpa.22619
dc.subject PGLS
dc.subject Platyrrhini
dc.subject Strepsirrhini
dc.subject adaptation
dc.subject dietary ecology
dc.subject discriminant function analysis
dc.subject mastication
dc.subject structural carbohydrate
dc.subject Animals
dc.subject Anthropology, Physical
dc.subject Discriminant Analysis
dc.subject Least-Squares Analysis
dc.subject Mastication
dc.subject Molar
dc.subject Primates
dc.title The effect of differences in methodology among some recent applications of shearing quotients.
dc.type Journal article
pubs.author-url http://www.ncbi.nlm.nih.gov/pubmed/25256698
pubs.begin-page 166
pubs.end-page 178
pubs.issue 1
pubs.organisational-group Duke
pubs.organisational-group Earth and Ocean Sciences
pubs.organisational-group Evolutionary Anthropology
pubs.organisational-group Nicholas School of the Environment
pubs.organisational-group Trinity College of Arts & Sciences
pubs.publication-status Published
pubs.volume 156
dc.identifier.eissn 1096-8644


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