Energetic Value of Women's Work: Assessing Maternal Energetic Costs From Acorn Foraging

Objectives

Perceptions of female energetic contributions and their role in human evolution are limited. This exploratory study compares energy expenditure, return rate, and foraging efficiency between infant carrying methods in females simulating acorn foraging practices by Indigenous communities in western North America.

Materials and Methods

After resting metabolic rate (RMR) was collected, female volunteers (n = 6, age: 21–37) conducted three 1-h bouts of acorn foraging. First, volunteers foraged unloaded (control) while for the second and third bouts they foraged carrying a traditional basketry cradle or a chest sling (randomized order) with 4.5 kg sandbags. Energy expenditure (EE) was measured through indirect calorimetry, physical activity intensity was assessed using accelerometry, and foraging return rates (RR) were calculated after acorn processing.

Results

The inter-bout results are not statistically significant. Findings show, however, that foraging RR largely surpasses EE irrespective of infant carrying method. The cradle carrying technique resulted in the largest mean EE, yet it was more efficient than the sling-carrying method. Most of the time foraging was spent at moderate physical intensity, especially during cradle-carrying bouts compared to the sling-carrying and control groups.

Conclusions

This small exploratory study demonstrates the caloric contributions by and foraging efficiency of females. Our findings emphasize that child-carrying techniques using basketry cradles allow for improved efficiency in foraging returns compared to more commonly used slings. Our results reinforce previous findings of female foraging efficiency despite the energetic demands of infant carrying and emphasize the energetic contributions of females to human evolution even during child-rearing.