Children learn to read others’ emotional expression rather slowly: of the set of internationally recognized facial expressions of emotion, only happiness is reliably recognized at ages 3 to 5, anger by age 7, fear by age 10, and surprise by age 11 (Massaro, 1998). Since both language and facial expressions of emotion suffer from signal deterioration (due to, for example, darkness, distance, poor reception, and averted face) children must learn to bridge ambiguity. They must observe, mimic, and practice not only productive skills but also social ones (Tomasello, 1993, 1999). Adult tolerance for social incompetence and support for learning (via exegesis of imitative behaviors, commands and instructions, and guided performance) create the space for social learning analogous to that created for production learning. Social skills will, if anything, be more critical to successful reproduction, and it is significant that rites of passage at adolescence emphasize implicit and explicit social instruction over or in conjunction with production.
Social relationships have high adaptive value, for they regulate access to resources. On the one hand are the tangible resources emphasized in life history analysis that constitute material capital: food, shelter, safety, labor, and mates. On the other hand are immaterial resources largely overlooked in life history theory and that comprise social capital: information, social connections and memberships, social support and opportunity, assistance and cooperation, coordination and triage, and economies of scale. Deferred reciprocities allow social capital to be translated into material capital at spatially and temporally remote situations. Conversely, material capital can be converted to social capital through sharing and obligation.
Information and opportunities to acquire information through observation, association, or assisted implementation are critical resources in human life history because they facilitate access to material and social resources. Information can be of durable or ephemeral value, but given the vicissitudes of social life and ecological circumstances, ephemeral knowledge of the immediate and transient contributes just as importantly to life history as does durable knowledge of people, places, and processes. Thus, the value of social relationships inheres also in access to information, which may be regarded as the third good in limited supply, after energy and time.
In sum, human ecology and social relationships largely define the context of individual life history and determine access to resources. Virtually all aspects of reproduction–mate acquisition, mating, fertility, parenting– are framed and mediated through social behavior and social ecology. Offspring viability is also shaped through social dynamics. The very low adult mortality on which human reproductive strategy relies depends heavily on