Evolutionary radiation of mid-Holocene lanceolate points from the highlands of the South Central Andes

Abstract

Through phylogenetic reconstruction this work analyzes the diversification of lanceolate points of the South Central Andes which began in the early Holocene and spanned the entire mid- Holocene. Based on a regional-scale data, we discuss the links between the increasing mid-Holocene risk conditions, the patterns of diversification of point lineages, demographic change and animal resources consumption. We distinguish a first instance of greater diversity of points, a higher rate of innovation and less class longevity. These trends progressively stabilized, giving rise to a pattern of less innovation, decreasing taxa diversity and greater class longevity as well as an age-related extinction pattern. We show that as projectile points diversified, hunting efficiency increased along the mid-Holocene by the increased representation of high-return fauna in the regional zooarchaeological record. We suggest that this diversification of lanceolate points was an adaptive evolutionary radiation which began with the increase in the rate of innovation for coping with the increasing risk of the beginning of mid-Holocene in the South Central Andes. From this we conclude that technological innovation was a prerequisite for the human specialization in camelid hunting and for the development of a highly economically efficient foraging strategy in the south Andean highlands.