Modeling growth and senescence in physical performance among the Ache of eastern Paraguay

This article seeks to partially fill a paucity of available data on physical performance in hunter-gatherer societies. Quantitative data are presented on various physical performance measures conducted on the Ache of eastern Paraguay, hunter-gatherers up to the 1970s and now part-time foragers and horticulturists. The performance battery was conducted on most individuals over 10 years of age, allowing for cross-sectional examination of growth and senescence patterns across the lifespan for both sexes. These measures tend to display steep ascents and peak in the early 20s with slight declines thereafter with age for males, whereas females demonstrate peaks in performance earlier in life, with lower or no senescence rates thereafter. The result is a convergence in physical performance between men and women at later ages. We suggest that the female physiology faces reproductive constraints to performance early in life but shifts allocation to increased work output later in life during the long human postmenopausal stage. In contrast, the male physiology maximizes work output in early adult life. These schedules of physical performance are contrasted with schedules of food production ability, which tend to occur later in life, and therefore imply that skill rather than strength alone is an important component of the human foraging niche.