Human Organizational Change and Climate Variability in Northwest Patagonia: the last 1000 years BP using a multi-proxy approach

ADOLFO F. GIL; GUSTAVO NEME; CLARA OTAOLA; NURIA SUGRAÑES; LAURA SALGÁN

Dublin

Congreso; INQUA; 2019

International Union for Quaternary Research

Although Northwest Patagonia was inhabited by hunter gatherer until historic times withevidence of ?farming islands? in the north sector (mostly Diamante and Atuel River).Until recent time the human evolutionary trajectory had been focused in a coarsegrained temporal resolution, using multi millennial units. This presentation explores thearchaeological record in relation with climate variation during the last 1000 years. Usinga paleocimatic reconstruction of SAM (Southern Annular Mode) we compare humandemography, diet, and technological organization. Different proxies indicate twodifferent scenarios. First, between 1000 to 1300 years AD, dominated by SAM positive,hotter and driest summers were associated with stable human population, low use ofhigh rank resources, like guanaco, and low frequency of non local rock and ceramics.Around 1400 years AD, start to dominate SAM negative, that implied cooler summerassociated with an increase in precipitation. An abrupt increase on human populationwas observed in a period of ca. 200 years (ca. 1400 to 1600 AD). In addition, a notableincrease in guanaco exploitation and significant change on stable isotopes trend onhuman bone (13C and 15N) indicate change in diet. An increase in a non-local rock likeobsidian and non-local ceramic are recorded too. Clearly, these changes wereoperating before LIA and before the Hispanic domination (recorded ca. 1800/1880 ADin the area, ca. 1550 in a macro region). All these findings point out that the lastmillennium, in Northwest Patagonia was not a stable socio-ecological system.Contrarily, we detect abrupt changes associated with an increase in humandemography and a significant increase in primary productivity as consequence of SAMnegative modulation that generated summers with more precipitation and cooler thannormal. This scenario of population growth in Patagonian hunter gatherers could causetheir expansion to the North, retracting the limits of prehispanic farming, just a fewcenturies before the Spanish arrived.