Relationship between subsistence and age at weaning in “preindustrial” societies

Abstract

Cross-cultural studies have revealed broad quantitative associations between subsistence practice and demographic parameters for preindustrial populations. One explanation is that variationin the availability of suitable weaning foods influenced the frequency and duration of breastfeeding and thus the length of interbirth intervals and the probability of child survival (the "weaning food availability" hypothesis). We examine the available data on weaning age variation in preindustrial populations and report results of a cross-cultural test of the predictions that weaning occurred earlier in agricultural and pastoral populations because dairy and cereal production increased the availability of easily digestible, nutrientrich foods appropriate for weaning. We found that, contrary to predictions, supplementation with liquid foods other than breast milk was delayed in agricultural populations relative to less agriculturally dependent ones and complementary feeding with solid foods was delayed in pastoral populations relative to those less dependent on herding. Although the duration of breastfeeding was longer in populations dependent on hunting, there was no qualitative evidence that such populations lacked foods appropriate for weaning. The patterns observed suggest that the relationships between demography and subsistence observed among preindustrial societies cannot be explained by the "weaning food availability" hypothesis. We discuss the implications for understanding the mechanisms underlying prehistoric human demography, subsistence shifts, allocation to parenting and mating effort, and the evolutionary implications of tradeoffs between diet and disease.

Reconstruction of breastfeeding and weaning practices using stable isotope and trace element analyses: A review

“…From the comparison of BWPs of skeletal and ethnographic populations, we concluded that weaning ages in nonindustrial human populations have no systematic pattern of variation over time and space during the Holocene. Our results, as well as a metaanalysis of the BWPs reported in ethnographic studies (Sellen and Smay, 2001), have indicated that weaning age did not differ according to subsistence. The increased availability of starchy weaning foods and animal milks produced by agricultural and pastoral activities in ancient populations is assumed to have facilitated early weaning, contributing to shorter birth intervals and increased fertility.…”

“…For example, ethnographic studies have indicated that liquids, such as fruits, teas, and cereal gruel with lower protein content are frequently used in the early weaning process in both modern and traditional human populations (WHO, 1998;Sellen and Smay, 2001). However, the d…”

Nutritional Phases in Prader-Willi Syndrome: Evolutionary and Clinical Interpretations

“…How could increased appetite in the absence of expression of PEGs be reconciled with the theoretical prediction that PEGs increase costs to mothers or their kin? The anthropological literature suggests that humans typically introduced supplemental foods at about six months, with cessation of breastfeeding in the third year [11]. If the onset of hyperphagia is in the second or third year, as envisaged in the two-phase model of PWS, then appetite increased at roughly an age at which our ancestors were being weaned from the breast.…”

Metabolic costs and evolutionary implications of human brain development

“…Compared with other great apes, human offspring are weaned early, leading to an extended period of dependence on procured resources rather than breast milk (1,4). Although this unique human reproductive pattern is viewed as shortening the interbirth interval and thus increasing fertility (5,6), what is less clear is why humans also grow so slowly during childhood.…”