Street art in Chapinero, Bogota, Colombia

Evidence for quantity–quality trade-offs, sex-specific parental investment, and variance compensation in colonized Agta foragers undergoing demographic transition

Drawing on the Agta Demographic Database, we conduct a Bayesian analysis of life-history traits, focused on sex-biased parental investment, birth-order effects, quantity-quality trade-offs, and adaptive fertility modulation in the Agta, a population undergoing a demographic and social/ecological transition from foragers to peasant laborers. We compare and contrast two geographic sub-divisions of the Agta population, a relatively isolated peninsular population and an acculturating mainland population, over two time periods. We find evidence of reliable demographic changes in: 1) offspring survival/parental investment by sex and birth-order, 2) maternal fertility, and 3) quantity-quality trade-offs, across these spatial and temporal categories. We interpret these responses to the transition from foraging to peasant agricultural labor from an evolutionary perspective. Additionally, we find partial quantitative evidence for adaptive, risk-sensitive fertility reduction. The multi-level Bayesian models used in our analysis allow us to integrate over uncertainty introduced by censored and missing data, and to partially pool information across clusters in the data. These models and their problem-specific derivations should be of broad interest to evolutionary anthropologists and demographers analyzing data sets with missing or censored information.

Read the paper online here or download a preprint here.

Bibtex:

@article{ross2016evidence,
  title={Evidence for quantity--quality trade-offs, sex-specific parental investment, and variance compensation in colonized Agta foragers undergoing demographic transition},
  author={Ross, Cody T and Mulder, Monique Borgerhoff and Winterhalder, Bruce and Uehara, Ray and Headland, Janet and Headland, Thomas},
  journal={Evolution and Human Behavior},
  volume={37},
  number={5},
  pages={350--365},
  year={2016},
  publisher={Elsevier}
}

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