Anselme and Güntürkün (A&G) propose a theoretical model for foraging behavior under uncertain and unpredictable environments that links increased foraging with increased fat and dopamine levels. In this commentary, we elucidate another common strategy used by animals and humans alike in face of environmental uncertainty: the collective strategy, which entails collaborative foraging efforts and food sharing. Previous sociobiological and anthropological studies have shown that food sharing with non-kin is common for both human and non-human societies, from small animals such as vampire bats (Wilkinson Reference Wilkinson1990; Winterhalder Reference Winterhalder1986) to apes (de Waal Reference de Waal1989) and human hunter-gatherer societies (Gurven Reference Gurven2004; Gurven et al. Reference Gurven, Hill, Kaplan, Hurtado and Lyles2000).

Researchers have proposed several social benefits of sharing resources, including costly signaling (Bleige Bird et al. Reference Bleige Bird, Smith and SBird2001; Hawkes et al. Reference Hawkes, O'Connell and Blurton Jones2001), and tolerated theft (Bird Reference Bird1997; Blurton Jones Reference Blurton Jones1987). However, the most prominent explanation of the collective strategy is the social insurance hypothesis. According to this explanation, by joining groups and sharing foraged outcomes, individuals can benefit from the law of large numbers, thereby decreasing the effect of uncertainty. That is, group members decrease the variability of their individual outcomes by aggregating and distributing the collective foraged amount. This hypothesis is supported by anthropological studies (Gurven Reference Gurven2004; Gurven et al. Reference Gurven, Hill, Kaplan, Hurtado and Lyles2000; Kaplan et al. Reference Kaplan, Hill, Cadeliña, Hayden, Hyndman, Preston, Alden Smith, Stuart and Yesner1985) and controlled laboratory experiments, which have demonstrated a causal relationship between (monetary) outcome variability and the tendency to join groups (Bone et al. Reference Bone, Hey and Suckling2004; Charness & Genicot Reference Charness and Genicot2009; Kaplan et al. Reference Kaplan, Schniter, Smith and Wilson2012; Suleiman et al. Reference Suleiman, Aharonov-Majar and Luzon2015). Suleiman et al. (Reference Suleiman, Aharonov-Majar and Luzon2015) found that the tendency to share resources in the face of risk existed even in one-stage interactions and was more pronounced when group-joining was framed as a way to avoid losses (as opposed as a way to make gains).

A&G make an important contribution by integrating two separate lines of research on individual risk reduction mechanisms – the psychological and the ecological. Because foraging efforts in small-scale human societies and non-human species are often pursued in groups, we propose to extend A&G's research by considering not only individual risk reduction mechanisms, but also the collective risk-sharing mechanism.

One approach is to view the two mechanisms as mutually exclusive. According to this approach, when faced with environmental uncertainty, individuals make a choice between foraging alone and joining groups to share their foraging outcomes with others. Evidence from experimental studies seems to support this approach. Suleiman et al. (Reference Suleiman, Aharonov-Majar and Luzon2015) gave participants the choice to participate in a gamble as individuals and gain the gamble's outcome or to join a group of a given size, pool the individual outcomes, and distribute them equally between the group members. A higher percentage of participants chose the group over the solitary gamble, particularly in gambles that were high risk (higher variance). Moreover, when under high risk, participants opted for larger groups over smaller groups, a tendency not observed under low risk. However, in another study, when participants were offered an alternative, individual mechanism for reducing variability (i.e., making multiple gambles) that is equivalent to increased foraging, the tendency to join groups disappeared (Suleiman et al. Reference Suleiman, Aharonov-Majar and Luzon2015).

The decision between foraging alone and as a group may depend on the type of resource. The individual strategy discussed in the target article might be optimal for some types of food, while a collective strategy might be optimal for others. Anthropological studies lend support to this conjecture by demonstrating that resources that are shared most among non-kin are those characterized by high outcome variability – such as meat – compared with collected goods, the supply of which is more stable (Gurven et al. Reference Gurven, Hill, Kaplan, Hurtado and Lyles2000; Kaplan et al. Reference Kaplan, Hill, Cadeliña, Hayden, Hyndman, Preston, Alden Smith, Stuart and Yesner1985). Another factor that may affect the choice of risk-reduction strategy is the level of trust between group members. Jimenez and Pietras (Reference Jimenez and Pietras2018) reported that when the probability of reciprocation was low, individuals engaged less in sharing.

Another approach concerning the conjunction of individual and group strategies for risk reduction is that increased individual foraging and collective resource sharing are complementary rather than mutually exclusive mechanisms. According to this view, when faced with environmental uncertainty, only some members of the group engage in increased foraging and share their outcomes with the rest of the group members. This conjecture could be tested by examining whether the surplus of foraged goods after increased foraging is more likely to be shared (because of group solidarity) or less likely to be shared (because of individual hoarding). In line with A&G's model, which links foraging under uncertainty with increased body fat, we expect that increased collective foraging (as part of a sharing effort), as opposed to increased individual foraging, will be associated with a decrease or no change in body fat.

Finally, pursuant to A&G's proposal that dopamine levels are correlated with individual motivations for seeking more food under uncertainty, research should address the physiological and neurological correlates of the motivation to form risk-sharing groups and sustain cooperative foraging behavior. Based on previous research, we suggest that food sharing is associated with increase in the level of the neuropeptide oxytocin, which is reported to elicit trust and cooperative behavior in humans (De Dreu et al. Reference De Dreu, Greer, Handgraaf, Shalvi, Kleef, Baas, Ten Velden, Van Dijk and Feith2010; Kosfeld et al. Reference Kosfeld, Heinrichs, Zak, Fischbacher and Fehr2005; Madden & Clutton-Brock Reference Madden and Clutton-Brock2011). Indeed, a recent study reported an increase in urinary levels of oxytocin following food sharing (Wittig et al. Reference Wittig, Crockford, Deschner, Langergraber, Ziegler and Zuberbuhler2014).

To summarize, we argue that the theoretical model proposed by A&G and the literature on the social insurance hypothesis can benefit each other by revealing a larger picture of human behavior under environmental uncertainty. Conceptualizing individuals as part of a group could explain not only the amount of foraging, but also the scope and range of foraging by different members in the group.