Can Differences in Strength Explain Observed Child Carrying Behavior in Men and Women?

Laura Stearns

Document Type

Senior Honors Project

Publication Date

5-2011

Abstract

Despite the frequency and necessity of child-carrying by adults, very little research has focused on the energetic costs and behavioral patterns associated with this activity. This study explores differences in physical capacity between females and males as a possible explanation for the observation that men are more commonly seen carrying children on their shoulders, while women tend to carry toddler-sized children on their hips. To address this issue, I measured the one-repetition maximum (1RM) of four large muscle groups in 5 female and 4 male participants (age 18-45 y). The 1RM procedure determines the largest mass a person can lift one time with correct form. Because the participants carried a toddler-sized manikin (11 kg) either on their shoulders or their hips, I chose four muscle groups related to these tasks: arm curl, bent-over row, leg press, and shoulder press. Males had higher 1RMs for all of the muscle groups than females (p values between 0.006 and 0.06). For the females, the toddler mass was 91%, 54%, 46%, and 11% of their 1RM for arm curls, bent-over row, shoulder press, and leg press, respectively, while for the males 50%, 31%, 16%, and 4%. The greater strength of their shoulder muscle group gives men, in general, a greater ability to lift children onto their shoulders. As demonstrated by the results hip-carrying for women might be a more manageable alternative, since a toddler would be near the limit of their single-arm curl strength. These results have implications regarding our predictions about child-carrying interactions in populations of contemporary humans as well as in groups of the earliest known humans.

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