Breastfeeding and weaning in Late Holocene hunter-gatherers of the lower Paraná wetland, South America.

OBJECTIVE: In this study, we analyze breastfeeding and weaning practices in pre-Columbian complex hunter-gatherers from the lower Paraná River basin (South America). MATERIALS AND METHODS: We carried out bone isotope analyses concerning δ13 C in collagen and apatite, the spacing between both carbon sources and δ15 N in a sample of 23 subadult and adult individuals of both sexes recovered from Late Holocene archaeological sites, ranging from 1665 ± 45 to 680 ± 80 14 C years BP. RESULTS AND DISCUSSION: The results indicate that exclusive breastfeeding continued until the age of ~2 years, and weaning probably until 4 years of age. Supplementary foods included C3 plants and probably animal fats and C4 carbohydrates. A high fractionation of 4.9‰ in δ15 N values was recognized between breastfeeding infants and adult females, perhaps reflecting episodic hyper-protein diets in women linked to men's food provisioning during women's gestational/postpartum period. Additionally, male adults present a higher protein intake than females. Although this difference is not statistically significant with the current sample size, it could be a clue related to a sexual division in food procurement.

Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation.

The causes of Late Pleistocene megafaunal extinctions (60,000 to 11,650 years ago, hereafter 60 to 11.65 ka) remain contentious, with major phases coinciding with both human arrival and climate change around the world. The Americas provide a unique opportunity to disentangle these factors as human colonization took place over a narrow time frame (~15 to 14.6 ka) but during contrasting temperature trends across each continent. Unfortunately, limited data sets in South America have so far precluded detailed comparison. We analyze genetic and radiocarbon data from 89 and 71 Patagonian megafaunal bones, respectively, more than doubling the high-quality Pleistocene megafaunal radiocarbon data sets from the region. We identify a narrow megafaunal extinction phase 12,280 ± 110 years ago, some 1 to 3 thousand years after initial human presence in the area. Although humans arrived immediately prior to a cold phase, the Antarctic Cold Reversal stadial, megafaunal extinctions did not occur until the stadial finished and the subsequent warming phase commenced some 1 to 3 thousand years later. The increased resolution provided by the Patagonian material reveals that the sequence of climate and extinction events in North and South America were temporally inverted, but in both cases, megafaunal extinctions did not occur until human presence and climate warming coincided. Overall, metapopulation processes involving subpopulation connectivity on a continental scale appear to have been critical for megafaunal species survival of both climate change and human impacts.