We examine age of weaning and childhood diet at a Middle Period site in central California, CA-SOL-11, near Suisun Marsh. Stable isotope analyses of serial samples of permanent first molars record information about the diet of an individual when they were between 0 and 9.5 years of age. Our results show that females were breastfed, on average, slightly longer than males at the site. Because breastfeeding represents a significant time and caloric investment by a mother, this suggests greater parental investment in female offspring relative to males. After weaning, young males gained a greater proportion of protein from higher trophic levels and with greater contribution from brackish or marine environments, which we interpret as a higher quality diet. This suggests either preferential provisioning by parents in males after weaning, or evidence of gendered labor practices and diets beginning in early childhood. We also incorporate new analyses of the amelogenin proteins preserved in enamel, AMELX_HUMAN and AMELY_HUMAN, to estimate the sex of one individual previously identified as male based on osteological markers and two individuals that could not be assigned sex based on osteology
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This content will become publicly available on July 11, 2024
Sex‐biased parental investment and female wealth accumulation in ancient California
The mortuary record at Middle Period site
With the consent of, and in collaboration with, the Muwekma Ohlone Tribe of the San Francisco Bay Area, this paper employs isotopic analysis (
The average weaning age for females at
Despite the small sample size often unavoidable in archaeological contexts, we find possible female‐biased parental investment strategies. Cessation of breastfeeding (weaning) was, on average, 5 months earlier for males compared to females. There are no differences between females and males in the consumption of supplemental or post‐weaning foods. Strontium data suggest a flexible postmarital residence system that favored matrilocality. This may have incentivized greater investment in female offspring.
- NSF-PAR ID:
- 10442130
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Biological Anthropology
- Volume:
- 182
- Issue:
- 1
- ISSN:
- 2692-7691
- Format(s):
- Medium: X Size: p. 109-125
- Size(s):
- ["p. 109-125"]
- Sponsoring Org:
- National Science Foundation
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Methods Serial dentin stable carbon and nitrogen isotope analyses from canines are compared between catastrophic (
n = 45) and attritional groups (n = 23). Canines are sectioned serially from crown to apex, and the increment's δ15N and δ13C are used to estimate age‐at‐weaning completion.Results Catastrophic and attritional groups exhibit similar age‐at‐weaning completion (~2.8 years). Seventy‐four percent of individuals lack elevated δ15N values in dentin that formed during infancy.
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Abstract Lactation length and weaning age provide important information about maternal investment, which can reflect the health and nutritional status of the mother, as well as broader reproductive strategies in mammals. Calcium‐normalized strontium (Sr) and barium (Ba) concentrations in the growth layers of mammalian teeth differ for nursing animals and those consuming non‐milk foods, thus can be used to estimate age‐at‐weaning. To date, this approach has been used only for terrestrial animals, and almost exclusively for primates.
The goal of this study was to determine whether Sr and Ba concentrations in the cementum of Pacific walrus
Odobenus rosmarus divergens teeth can be used to estimate weaning age. Teeth from 107 walruses were analysed using laser ablation inductively coupled plasma mass spectrometry, and calcium‐normalized88Sr and137Ba concentrations were quantified.For most walruses, both Sr and Ba concentrations exhibited rapid changes in early life. Ba concentrations matched closely with expected patterns in the published literature, rapidly declining from high to low concentrations (typically from ~10 ppm to ~5 ppm). In contrast, Sr exhibited a pattern opposite to that presented in studies of terrestrial mammals, appearing nearly identical to Ba (typically declining from ~400 ppm to ~200 ppm). To explain these findings, we present conceptual models of the factors generating weaning signals in Sr and Ba for terrestrial mammals, as well as a new, hypothetical model for walruses. Both a visual and mathematical approach to weaning age estimation indicated a median weaning age of walruses at the end of the second year of life (in the second dark layer of the tooth cementum), with many walruses estimated to have weaned in their third year of life, and a smaller group weaning in their fourth or fifth year. This is later than expected, given a published estimate of walrus weaning at 18–24 months.
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