Isotopic evidence of weaning in hunter-gatherers from the late holocene in Lake Salitroso, Patagonia, Argentina

ABSTRAC Objectives:The timing and duration of breastfeeding and weaning in past hunter-gatherer populations are discussed based on the results of stable carbon and nitrogen isotope analyses undertaken on a Late Holocene skeletal sample from Lake Salitroso in the Patagonian steppe (Argentina). Research in Lake Salitroso is part of a regional project that studies the relationship between hunter-gatherer societies, their organizational systems and the environmental changes during the last 3,000 years in Patagonia. Methods:The sample included 52 individuals: 33 subadults and 19 adults of both sexes. They were recovered from 24 burial stone structures, locally called chenques, with dates ranging from ca. 800 BP to 350 BP. Ribs were selected for collagen extraction and measurement of C-13/C-12 and N-15/N-14 ratios. Results:A C-13 mean value of -18.7 +/- 0.5 parts per thousand was obtained, with a range between -19.8 parts per thousand and -17.1 parts per thousand whereas N-15 recorded a mean of 11.9 parts per thousand +/- 1.1 parts per thousand with a range between 10.1 parts per thousand and 14.8 parts per thousand. N-15 data showed an age-related pattern with particularly marked difference between values for subadults under the age of 4 and older individuals. As opposed to N-15, C-13 showed little variation with age. Conclusions:An early incorporation of supplementary solid food between 0.75 and 2 years of age and a late cessation of breastfeeding at about 5-6 years of age were inferred. This suggests that among this Patagonian hunter-gatherer population weaning was a gradual and lengthy process. These results are consistent with the patterns observed in cross-cultural studies and archaeological samples of hunter-gatherer groups. Am J Phys Anthropol 158:105-115, 2015. (c) 2015 Wiley Periodicals, Inc.