The (mis)use of adult age estimates in osteology

Abstract

Context: Adult age-at-death is presented in a number of different ways by anthropologists. Ordinal categories predominate in osteoarchaeology, but do not reflect individual variation in ageing, with too many adults being classified as “middle adults”. In addition, mean ages (derived from reference samples) are overly-relied upon when developing and testing methods. In both cases, “age mimicry” is not adequately accounted for.

Objectives: To highlight the many inherent biases created when developing, testing and applying age-estimation methods without fully considering the impact of “age mimicry” and individual variation.

Methods: The paper draws on previously published research (Web of Science, Pub Med, Google Scholar) on age estimation methods and their use in anthropology.

Results and conclusions: There is a lack of consistency in the methods used to estimate age and for the mode of combining them. Ordinal categories are frequently used in osteoarchaeology, whereas forensic anthropologists are more likely to produce case-specific age ranges. Mean ages reflect the age structure of reference samples and should not be used to estimate age for individuals from populations with a different age-at-death structure. Individual-specific age ranges and/or probability densities should be used to report individual age. Further research should be undertaken on how to create unbiased, combined method age estimates.

• Age categories
• age estimation
• age range
• biological age
• mean age

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Erratum

Acknowledgements

I thank the following people for many delightful and thoughtful discussions about age estimation: Sonia Zakrzewski, George Milner, Svenja Weise, Niels Lynnerup, Chiara Villa, Andrew Chamberlain and the Lauchheim and Basel study group. Julia Beaumont and Hannah Koon kindly discussed aspects of this paper with me. I am indebted to students on the MSc Human Osteology and Palaeopathology and PhD students at the University of Bradford, who have challenged my perceptions of age estimation and inspired me to write this paper. I also thank the anonymous reviews for their insightful comments on an earlier draft of this paper. Any errors remain my own.

Declaration of interest

The author reports no conflicts of interest. The author alone is responsible for the content and writing of this article.