A cost for signaling: do Hadza hunter-gatherers forgo calories to show-off in an experimental context?

Hadza food-sharing is extremely generous and often extends to individuals outside the household. Some anthropologists have proposed that individuals, especially men, share food beyond the household in order to signal foraging skill. While correlational data have been used to both evidence and critique this hypothesis, it has less often been experimentally tested. Here, we conducted an incentivised experiment to test whether Hadza adults are indeed willing to forgo caloric resources in order to signal their foraging skills. In this study, 196 Hadza adults were given the opportunity to participate in two games - an aim game and a search game - designed to advertise their skill as foragers. We varied the incentive structure of both games, adjusting i) whether there was a caloric cost (i.e., honey) to play, and ii) whether success in each game was rewarded with a prize (i.e., a colored bracelet), which functioned as a visible signal of skill. Although the aim game was universally popular when there was no cost to play, we found that individuals generally valued calories more than signaling opportunities and were unwilling to forgo caloric resources to continue participation in either game. In line with signaling theory, we did observe age and gender difference in willingness to wager calories for signaling opportunities. Men were more likely than women to forgo calories in order to participate. Younger people (<37), especially younger men, were also more likely to forgo calories to play than older people.