Substitute Parents: Biological and Social Perspectives on Alloparenting in Human Societies (review)

Investigators of ecology and evolutionary biology have extensively explored the involvement of parents and other kin in the care provided to juveniles. This has led to many empirical and theoretical advances in our understanding of the parent-offspring conflict, kin selection, and the evolution of sociality and altruism. In humans, however, investigating the role played by adults in child care, according to their gender and how they are related to the child, has proved difficult. As a consequence, the emergence of alloparental behaviors during human evolution is yet unsolved. This is because humans are highly social, long-lived, iteroparous, and dimorphic and because they care for children of different ages at the same time and show many unusual life-history traits. Other factors are the peculiar evolution of the hominins and the many uncertainties concerning human origins, the complexity of socioeconomic relationships between individuals within and between families, and, most of all, the variation of these across cultures and through time. More than in any other species, a multidisciplinary approach is therefore needed to investigate alloparental care in humans, and we should therefore welcome Substitute Parents, which, as the editors put it, "brings together a variety of contributors who can cover the topic of alloparenting from widely different perspectives."

Substitute Parents opens with an excellent review, by N. G. Solomon and L. D. Hayes, of alloparental behaviors in ecology. In this review Solomon and Hayes give a structured panorama of the alloparenting strategies across vertebrates and discuss with pedagogy the evolutionary theories of alloparenting. This chapter, together with S. Hrdy's prologue and the editors' introduction, sets the scene for the ecologic and evolutionary theater in which human behaviors play. This theoretical background agreeably echoes throughout the 14 following chapters, which address the fundamental questions of parenting and substitute parenting in humans: Who is caring for the children and to what extent? What are the social and biological costs and benefits for the parents and the substitute parents? What are the social and biological costs and benefits for the child? How do these vary cross-culturally?

The first set of chapters aims to measure the investment of kin in child care and/or to estimate the effect that kin investment (or the lack of it) has on the child, from the physiological and psychological level to that of survival and reproduction. Measures of investment are mainly encompassed by estimates of the time and resources allocated by kin in child care (the Maya population of Mexico, studied by K. L. Kramer; and the Toba population of Argentina, studied by C. R. Valeggia). Effect of kin and/or nonkin investment on children is estimated by means of phenotypic (anthropometric and endocrinal) and demographic variables (the rural population of Gambia, studied by R. Sear and R. Mace; and the population of Dominica, studied by M. V. Flinn and D. Leon) and behavioral observations (contemporary U.K., studied by J. Bensel). These quantitative approaches are nicely combined with more qualitative analyses aimed at identifying nonparental caregivers (A. Gottlieb on the Beng population of Ivory Coast), performing a cross-cultural comparison of parenting and substitute parenting between northern and southern countries (H. Penn), and discussing how puzzling adoption is in light of evolutionary theory (D. Howe).

The last set of chapters, which are more oriented toward sociology and public policies, analyze the psychosocial consequences of surrogacy (in the contemporary U.K., studied by E. Lycett), divorce (in the contemporary U.K., studied by M. Robinson, L. Scanlan, and I. Butler), and child care services (in the contemporary United States, studied by J. Belsky); ask whether schools can be seen as substitute parents (contemporary U.K., studied by B. Mayall); analyze the socioeconomics factors that determine the use of child care services (contemporary U.K., studied by G. Paull); and investigate how the need for alloparenting has increased in response to the AIDS pandemic...