Clara Otaola

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

Patagonian megafaunal extinctions reveal synergistic roles of climate change and human impacts. 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.

Patch Choice, Landscape Ecology, and Foraging Efficiency: The Zooarchaeology of Late Holocene Foragers in Western Argentina

Abstract Different but complementary foraging adaptations existed in the Payunia volcanic and the Andean highland (or mountain) subregions of southern Mendoza, Argentina during the late Holocene. We employ an evolutionary ecological perspective to study the zooarchaeology of foraging adaptations after 4000 BP. Seasonal exploitation of guanaco (Lama guanicoe Müller) in the mountains appears to have been sustainable, which relates to high productivity of mountain river valley bottoms during the late Holocene. The mountains were a productive, seasonally available resource patch. A greater diversity of fauna in the Payunia subregion resulted in a different foraging strategy with larger diet breadth. Despite mounting evidence that human population growth occurred during the late Holocene, there is little evidence of resource depression of high-ranked resources, such as the guanaco. Application of foraging theory models in this context clarifies that hunting decisions occurred in the context of two factors, strategies informed by traditional ecological knowledge and the context of landscape ecology.