In many societies, children take care of infants and supervise toddlers, while the mother works on crops, on food preparation, or supervises livestock (Weisner and Gallimore, 1977; Kramer, 2005a,b; Hrdy, 2009). In others, children are the main supervisors of the livestock, even at some cost to their growth (Sellen, 2000, p. 15). In a few, children do little more than play, but often in games related to subsistence and childcare (Briggs 1970; Draper and Cashdan, 1988). Sear and Mace (2008) report older children as effective helpers in five out of six “statistically adequate” studies. In much the same way as Hawkes et al. (1998) had suggested that the combination of the mother's and grandmother's productivity might allow the great fertility of humans compared to our nearest primate relatives, Kramer (2005a,b) and Kramer and Ellison (2010) point to the contributions of child helpers.

Child helpers originally attracted the attention of evolutionary-minded anthropologists because of an obvious analogy to avian helpers at the nest (Turke, 1988), and as a context in which to look at consequences of kin selection. Such analogies can be useful provocations but are seldom exact models. As well as paying attention to current ideas, each of us needs to think anew about likely costs and benefits in the setting in which we are working. The varied circumstances of different populations will shape different costs and benefits for the mother, for the child helper, and for the recipients of help.

My primary task in this chapter is to test whether Hadza children enhance the growth and survival of younger siblings, and the fertility of their mother. I set aside some obvious issues like help from cousins or uncles and aunts who are still children. Cousins may have their own young siblings, closer kin than our under-five-year-old subjects. The small and vulnerable children presumably gain from any help they can get, and Hrdy (2009, as well as Burkart et al., 2009) and Hawkes (2014) draw attention to possible broad implications of selection on the ability of young children to enlist help from a variety of people. The mother also presumably gains from any help she can get, unless her fitness is reduced by her older children incurring serious costs from trying to help, as may be the case when child foraging is dangerous.