Accurate age estimation in small-scale societies

Yoan Diekmann*, Daniel Smith, Pascale Gerbault, Mark Dyble, Abigail E. Page, Nikhil Chaudhary, Andrea Bamberg Migliano, Mark G. Thomas

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

32 Citations (Scopus)
286 Downloads (Pure)


Precise estimation of age is essential in evolutionary anthropology, especially to infer population age structures and understand the evolution of human life history diversity. However, in small-scale societies, such as hunter-gatherer populations, time is often not referred to in calendar years, and accurate age estimation remains a challenge. We address this issue by proposing a Bayesian approach that accounts for age uncertainty inherent to fieldwork data. We developed a Gibbs sampling Markov chain Monte Carlo algorithm that produces posterior distributions of ages for each individual, based on a ranking order of individuals from youngest to oldest and age ranges for each individual. We first validate our method on 65 Agta foragers from the Philippines with known ages, and show that our method generates age estimations that are superior to previously published regression-based approaches. We then use data on 587 Agta collected during recent fieldwork to demonstrate how multiple partial age ranks coming from multiple camps of hunter-gatherers can be integrated. Finally, we exemplify how the distributions generated by our method can be used to estimate important demographic parameters in small-scale societies: here, age-specific fertility patterns. Our flexible Bayesian approach will be especially useful to improve cross-cultural life history datasets for small-scale societies for which reliable age records are difficult to acquire.
Original languageEnglish
Pages (from-to)8205-8210
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number31
Early online date10 Jul 2017
Publication statusPublished - 1 Aug 2017


  • Bayesian age estimation
  • Fertility
  • Gibbs sampler
  • Hunter-gatherers
  • Life history


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