What do we know about extended families and kinship networks? What gaps in our knowledge most need to be filled? How can we best organize current work and identify priorities for future research? These questions are important for several reasons: households in developing countries depend on friends and relatives for their livelihood and sometimes their survival; help exchanged within extended families and kin networks affects the distribution of economic well-being, and this private assistance and exchange can interact with public income redistribution. Yet despite rapid recent progress there remain significant deficiencies in our understanding of the economics of extended families. Researchers confront a large and sometimes bewildering array of findings. We review and assess this literature by starting with an emphasis on standard economic concerns, most notably the possible interaction between government-provided social insurance and private kinship networks. Our review of the evidence suggests the specter of complete “crowding out,” whereby introduction or expansion of public transfers merely supplants private transfers, is exceedingly remote, though not impossible. However, numerous studies do suggest partial—but nonetheless substantial—crowding out, on the order of a 20-to-30-cent reduction in private transfers per dollar increase in public transfers. But the range of estimated effects is exceedingly wide, with many studies suggesting little private transfer response at all. Reconciling and explaining these disparate findings is a priority for future research. Theorizing about the economics of families should move beyond its concentration on income effects. The empirical literature indeed indicates that non-economic variables, such as demographic factors, can have a powerful association with private transfers. We suggest that economists tap into the extensive non economic literature that takes an evolutionary approach to the family. We show that this literature provides valuable guidance for modeling demographic effects in the interactions among extended family members. The evolutionary literature has much to offer economists interested in family behavior by proposing novel interpretations of existing findings and pointing out new and fruitful directions for future research. We encourage economists to pay more attention to this approach when studying kinship networks.