same bedroom, but today each child needs his or her own room. Very little is known about how individual decisions are made and how social standards evolve regarding investments in children.

The same can be said of allocations to a person’s own consumption. We do not know why members of the elite in all societies engage in and institutionalize elaborate displays of consumption (Boone and Kessler, 1999). We also have a very incomplete understanding of the preferences and decision-making processes underlying consumption patterns in modern societies. Given limited budgets, decisions about one’s own and one’s children’s consumption impinge on fertility decisions.

With respect to the second major theme in this chapter, mating systems and parental investment by sex, our understanding is even more incomplete. The factors affecting convergence and divergence between the sexes in each of those allocation decisions have not yet been systematically investigated. Clearly humans exhibit a great deal of flexibility in their family arrangements; the relationships between allocation decisions by sex, mating markets, and socioeconomic conditions are a new frontier for research.

These considerations suggest a “two-pronged” research program. One prong is to understand the mechanisms underlying those allocation processes, and the other is to understand how those mechanisms interact with socioeconomic conditions in generating behavioral and demographic outcomes. Several distinct lines of research may each contribute to such an understanding.

One approach is to examine individual variation in the weights or relative values that people attach to changes in their own and their children’s consumption, to relative social standing, to sexual gratification, and to number of children. It would be useful to know if some portion of that variation is associated with additive and nonadditive genetic variation. Rather than simply examining the heritability of fertility per se, a productive direction for genetic mapping and behavioral genetics research may be to examine psychological characteristics hypothesized to be directly or indirectly involved in fertility and mating decisions. For example, it has been suggested that natural selection has resulted in a desire for sexual gratification but not for children per se (Potts, 1997). However, this has not been examined empirically although there is some evidence that high male status in contemporary society correlates with a man’s number of sexual encounters but not reproductive success (Vining, 1986).

Developmental research on the ontogeny of decisions regarding consumption, fertility, sexual fidelity, and investment in children would also be useful. Do experiences taking care of infants and children during childhood and adolescence, investment of time and resources by parents, marital status of parents, exposure to media, and school composition affect desired levels of consumption and desire to have and/or rear children? To what

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