ABSTRACT
A contemporary evolutionary perspective suggests that humans probably evolved to discriminate in their solicitude towards kin, based on factors including degree of relatedness, certainty of relatedness, access to resources and reproductive value. This chapter examines if North American grandparents behave in a way that is consistent with the hypothesized predictions from kin selection theory. Grandparents living with their grandchildren were excluded because cohabitation makes extensive grandparent-grandchild interaction almost unavoidable, removing much of the grandparent's choice of interaction time. Resources increase his ability to sustain sexual relationships with more than one woman, thereby potentiating more children with the additional partners. B. R. Tinsley and R. D. Parke reported that greater grandparental contact with infants was associated with higher scores on the Bayley Scales of Infant Development, and this finding suggests a relationship between grandparental investment and grandchildren's successful development. Bilineal grandparents lived no closer to their uterine grandchildren, however, so distance does not account for the difference.
