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Comparing methods for analysing mortality profiles in zooarchaeological and palaeontological samples
Author(s) -
Steele T. E.
Publication year - 2005
Publication title -
international journal of osteoarchaeology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 60
eISSN - 1099-1212
pISSN - 1047-482X
DOI - 10.1002/oa.795
Subject(s) - confidence interval , cervus , geography , cervus elaphus , statistics , zooarchaeology , demography , biology , physical geography , archaeology , mathematics , ecology , sociology
In this study, I examine three methods that are currently used for comparing mortality profiles from zooarchaeological and palaeontological samples: (1) histograms with 10% of life‐span age classes; (2) boxplots showing tooth crown height medians; and (3) triangular plots of the proportions of young, prime and old animals. I assess the advantages and disadvantages of each method using data collected on two samples of Northern Yellowstone elk ( Cervus elaphus nelsoni ) with known, or cementum annuli‐determined, ages at death. One sample was hunted by wolves (n = 96), and the other was hunted by recent humans using rifles (n = 226). I tested each method with the known or cementum annuli age distributions and with age estimation techniques appropriate for archaeological assemblages. Histograms are best used when the relationship between dental eruption/attrition and age is well established so that individuals can be confidently assigned into 10% of life‐span groups, and when more than 30 or 40 individuals are present in the assemblage. Boxplots employ raw crown heights, thus removing the error introduced by assigning specimens to age classes, and therefore they allow the analysis of species where the relationship between dental eruption/attrition and age is unknown. Confidence intervals around the medians allow samples to be statistically compared. Triangular plots are easy to use and allow multiple samples and species to be considered simultaneously, but samples cannot be statistically compared. Modified triangular plots bootstrap samples to provide 95% confidence ellipses, allowing for statistical comparisons between samples. When possible, samples should be examined using multiple methods to increase confidence in the results. Copyright © 2005 John Wiley & Sons, Ltd.