Weaning and Early Childhood Diets at Two Early Period Sites: Implications for Parental Investment and Population Growth in Central California

Shifting weaning practices in Early Neolithic Cis‐Baikal, Siberia: New insights from stable isotope analysis of molar micro‐samples

“…Assuming culturally and/or spatially related populations would experience the same sets of challenges may not be valid, as shown in California contemporaries (Eerkens et al, ). The long‐term survival of the EN Kitoi culture suggests a population able to accommodate these potential challenges.…”

“…The increasing weaning duration has ramifications for the overall group size and rate of regional population growth during the EN. Increasing breastfeeding duration improves survival rates under conditions of moderate extrinsic risks, reduces the overall fertility of the female population, and so slows long‐term population growth (Borgerhoff Mulder, , ; Eerkens et al, ; Hill, ; Hrdy, ; Quinlan, , ; Waters‐Rist et al, ). The caveat being the extent to which the assumption that extrinsic risk conditions were low to begin with and increased as fish consumption increased.…”

“…Instead, δ 13 C tracks changes in the carbon source of dietary protein and routing through different food webs which in Cis‐Baikal helps to differentiate between terrestrial and aquatic foods, and parse out different fisheries (Weber et al, ), based on the length of the food webs in different types of watercourses (e.g., small mountain rivers, large mature rivers, lake‐shore, and deep‐water lake). In this regard, δ 13 C will primarily help to inform on post‐weaning foods and diet breadth during the first decade of life (Drucker & Bocherens, ; Tsutaya, ), and hopefully shed light on the presence, or absence, of specialised child diets or evidence of child foraging (Eerkens et al, ; Greenwald et al, ; Tsutaya, Sawada, Dodo, Mukai, & Yoneda, ).…”

“…Greenwald et al (; Eerkens et al, ) discuss how shifting weaning ages correlate to changing conditions combining risks from natural hazards (including violence and predation), risks of resource failure or shortfall, with the ambient pathogen loads of the environment. Under conditions that are extrinsically high or low risk, the added value of additional parental investment in the form of extended breastfeeding is minimal, unlikely to alter the survival of their children.…”

“…Parental behaviour related to breastfeeding is an important element in understanding cultural aspects of investment in children and population level fertility. Lactation is energetically expensive, as the mother is feeding a second individual out of her nutritional intake, and lowers female fertility, impacting short-term birth-spacing and long-term population growth (Bentley, 1985;Borgerhoff Mulder, 1992;Borgerhoff Mulder, 2000;Dettwyler, 2004;Eerkens et al, 2017;Hill, 1993;Kaplan, 1996;Tsutaya & Yoneda, 2015). The relative costs will be correlated to the prevalence of disease, risks of resource shortfalls, and other environmental hazards, thus, the length of weaning is hypothesised to fluctuate with changing circumstances throughout the EN.…”