The Impact of the Arid Diagonal on the Development of Pastoralism in the Central and Southern Andes of South America

MARSH, ERIK J.

Karratha

Congreso; 5th Southern Deserts Conference; 2018

The dry diagonal is one of the most significant ecological boundaries in South America. It extends southeast from the hyperacid Atacama desert and crosses the Andes. It has played a major role in plant and animal interaction and speciation in the Quaternary, including human occupations of the Andes during the Holocene. This paper focuses on its impact on the development of pastoralism. North of the dry diagonal, agropastoralism emerged as a rapid and profound change ~3540 cal BP, with similar archaeological evidence from the northern Lake Titicaca Basin in Peru to the Salar de Atacama in northern Chile. South of the dry diagonal, there is no clear evidence of agropastoralism until more than one thousand years later, ~2180 cal BP, and evidence is much sparser. This paper proposes that the dry diagonal played a central role in the differences between northern and southern agropastoralism in the Andes. It probably functioned as a barrier between human populations. Additionally, it marks the boundary between the summer and winter rainfall zones. Agropastoral annual schedules are closely tied to crops adapted to the summer rainfall zone in the north, so novel crop schedules would have been required in the winter rainfall zone in the south. This may also be related to the much lower population densities south of the dry diagonal.