This paper presents an analysis of the characteristics of men who become stepfathers, and their subsequent fertility patterns and lifetime reproductive success. Because women who already have children are ranked lower in the marriage market than women without children, men who marry women with children (e.g., stepfathers) are likely to have lower rankings in the marriage market as well. Using retrospective fertility and marital histories from the Panel Study of Income Dynamics (PSID), I show that men who become stepfathers have (...) lower levels of education, less income, and are more likely to have been divorced before and to already have children, all characteristics that lower their rankings in the marriage market. Men with one or two stepchildren are just as likely to have children within a marriage as non-stepfathers, although men with three stepchildren show decreased fertility. Among men age 45 and older, stepfathers have lower lifetime fertility than non-stepfathers, although the difference disappears when men’s age at first marriage is controlled for. Additionally, stepfathers have significantly higher fertility than men who never marry. The results suggest that some men become stepfathers to procure mates and fertility benefits that they would otherwise have been unlikely to obtain; for these men, raising other men’s children serves as a form of mating effort. (shrink)

Household structure may have strong effects on reproduction. This study uses household demographic data for 59 women in a Caribbean village to test evolutionary hypotheses concerning variation in reproductive strategies. Father-absence during childhood, current household composition, and household economic status are predicted to influence age at first birth, number of mates, reproductive success, and pair-bond stability. Criterion variables did not associate in a manner indicative of r- and K-strategies. Father-absence in early childhood had little influence on subsequent reproduction. Household wealth (...) and alloparenting were positively associated with age at first birth. Alloparenting was negatively associated with reproductive success. Women in long-term conjugal unions had higher reproductive success than did single women. Number of adult male kin resident in the household was negatively associated with women’s number of mates. (shrink)

Birth order has been examined over a wide variety of dimensions in the context of modern populations. A consistent message has been that it is better to be born first. The analysis of birth order in this paper is different in several ways from other investigations into birth order effects. First, we examine the effect of birth order in an egalitarian, small-scale, kin-based society, which has not been done before. Second, we use a different outcome measure, fertility, rather than outcome (...) measures of social, psychological, or economic success. We find, third, that being born late in an egalitarian, technologically simple society rather than being born early has a positive outcome on fertility, and fourth, that number of older siblings and sibling set size are even stronger predictors of fertility, especially for males. (shrink)

Data from the Kipsigis of Kenya are used to test two models for how parents invest in offspring, the Trivers-Willard and local resource competition/enhancement hypotheses. Investment is measured as age-specific survival, educational success, marital arrangements, and some components of property inheritance, permitting an evaluation of how biases persist or alter over the period of dependence. Changes through time in such biases are also examined. Despite stronger effects of wealth on the reproductive success of men than women, the survival of sons (...) and daughters is not related to parental wealth. However, a Trivers-Willard effect characterizes educational investment: poor families show a greater concern for daughters’ (vis-à-vis sons’) schooling than do rich families, a trend that has increased over time. In regard to models of local resource competition and enhancement, men’s reproductive success decreases with number of brothers and increases with number of sisters; this pattern of competition with same-sex sibs and cooperation with opposite-sex sibs is not found among women. As predicted from these observations, parents show reduced investment in sons with a large number of brothers, and increased investment in sons with a large number of sisters. By contrast, investment in daughters is entirely unaffected by number of sisters and is influenced only in subtle ways by number of brothers. Levels of investment in relation to sibship size (irrespective of siblings’ sex) are highest for younger children of large sib sets.Discussion of the results in relation to those from other studies leads to three conclusions. First, predictive models for how investment biases vary across societies must consider a broad range of socioecological factors constraining parental options and payoffs. Second, the timing of investment biases within societies will be affected by the value of children and the costs of parental investment. Third, measures of investment appropriate for between-sex and between-class comparisons need careful attention. Each of these issues is brought to bear on the question of why, in contrast to so many other parts of the world, sex preferences are so muted in Africa. (shrink)

We describe food transfer patterns among Ache Indians living on a permanent reservation. The social atmosphere at the reservation is characterized by a larger group size, a more predictable diet, and more privacy than the Ache typically experience in the forest while on temporary foraging treks. Although sharing patterns vary by resource type and package size, much of the food available at the reservation is given to members of just a few other families. We find significant positive correlations between amounts (...) transferred among pairs of families, a measure of the "contingency" component required of reciprocal altruism models. These preferred sharing partners are usually close kin. We explore implications of these results in light of predictions from current sharing models. (shrink)

In this paper we examine the merit of bargaining theory, in its economic and ecological forms, as a model for understanding variation in the frequency of participation in cooperative fishing among men of Ifaluk atoll in Micronesia. Two determinants of bargaining power are considered: resource control and a bargainer’s utility gain for his expected share of the negotiated resource. Several hypotheses which relte cultural and life-course parameters to bargaining power are tested against data on the frequency of cooperative sail-fishing participation. (...) Consistent with predictions generated from bargaining theory, we show that (1) age is negatively correlated with cooperative fishing participation, (2) men of highranking clans and men with high levels of education fish less than men of low-ranking clans and less-educated men, (3) men with high expected utility gains from fishing returns fish more than men with low expected utility gains, (4) number of dependents is positively correlated with cooperative fishing participation, and (5) the number of young genetic offspring residing with a man is positively correlated with cooperative fishing participation, whereas the number of genetic offspring more than 13 years old who are residing with a man is negatively correlated with cooperative fishing participation. (shrink)