Does Kin-Selection Theory Help to Explain Support Networks among Farmers in South-Central Ethiopia?

Social support networks play a key role in human livelihood security, especially in vulnerable communities. Here we explore how evolutionary ideas of kin selection and intra-household resource competition can explain individual variation in daily-support network size and composition in a South-Central Ethiopian agricultural community. We consider both domestic and agricultural help across two generations with different large-wealth transfer norms that yield different contexts for sibling competition. For farmers who inherited land rights from family, first-borns were more likely to report daily support from parents and to have larger non-parental kin networks (n=176). Compared with other farmers, first-borns were also more likely to reciprocate their parents’ support, and to help non-parental kin without reciprocity. For farmers who received land rights from the government (n=150), middle-born farmers reported more non-parental kin in their support networks compared with other farmers; non-reciprocal interactions were particularly common in both directions. This suggests a diversification of adult support network to non-parental kin, possibly in response to a long-term parental investment disadvantage of being middle-born sons. In all instances (with or without land inheritance), last-born farmers were the most disadvantaged in terms of kin support. Overall, we found that non-reciprocal interactions among farmers follow predictions of kin selection, and were more common for kin versus non-kin, and for close kin versus distant kin. Direct reciprocity explained a substantial part of the support received from kin, suggesting the importance of the combined effects of kin selection and reciprocity for investment from kin.