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SummaryTubal ligation is the modal form of family planning among American women aged 30 and older. As the preference for tubal ligation over cheaper, lower risk and more reliable methods, such as vasectomy, has puzzled experts, a theoretical approach that explains this preference would be useful. The present study investigates the high prevalence of voluntary sterilization among American women from the perspective of life history theory, arguing that the trade-offs between investing in current and future offspring will favour tubal ligation when women cannot obtain reliable male commitment to future parental investment. Data came from the National Survey of Fertility Barriers (NSFB), a nationally representative survey of 4712 American women aged 25–45 conducted between 2004 and 2007. Four novel predictions of the prevalence of tubal ligation, drawn from life history theory, were developed and tested: 1) it is most common among unpartnered women with children, and least common among married women with children; 2) it is negatively correlated with age at first birth; 3) it is least common among highly educated women without children, and most common among less educated women with children; and 4) among women with two or more children, it is positively correlated with lifetime number of long-term partners. These predictions were tested using multivariate regression analysis. The first prediction was not supported: women with children were more likely to be sterilized, regardless of their marital status. The other three predictions were all supported by the data. The results suggest that trade-offs influence women’s decisions to undergo voluntary sterilization. Women are most likely to opt for tubal ligation when the costs of an additional child will impinge on their ability to invest in existing offspring, especially in the context of reduced male commitment.

Although the vulnerability of young people to HIV/AIDS continues to be a serious concern in South Africa, no research has used a representative sample of South African youth to examine whether individual HIV risk perceptions change over time and, if they do, what factors are associated with change. Using data from the Cape Area Panel Study, a multi-racial, longitudinal study of youth and their households, this study examined whether youth change their HIV risk perceptions over a four-year period and whether sexual behaviors, knowing someone with HIV, gender and race are associated with any change. Overall, changes in HIV risk perceptions tend to be small. As predicted, sexual activity is associated with increases in risk perceptions. Contrary to predictions, condom use at last sex is associated with increases in risk perceptions and knowing someone with HIV is associated with decreases in risk perceptions. In addition, there is variation by gender and by race in the factors associated with change in risk perceptions. This study serves as an initial examination of change in the HIV risk perceptions of South African youth; further investigation of their HIV risk perceptions over time is needed.Keywords: HIV/AIDS, Risk Perceptions, First Sex1. INTRODUCTIONIn recent years, hopeful signs regarding the HIV/AIDS epidemic among young people in South Africa have emerged. HIV prevalence among young people in South Africa appears to be stabilizing. For 15- 24 year-olds, national HIV prevalence rates were estimated at 9.3% in 2002, 10.3% in 2005 and 8.7% in 2008, the most recent year for which national HIV prevalence data are available (Shisana and Simbayi, 2002; Shisana, 2009). HIV incidence appears to have declined in recent years among teenage males and females and 20-24 year-old females (Fraser-Hurt et al., 2011), which has been attributed to increases in condom use among young people (Shisana, 2009).In spite of these encouraging trends, the vulnerability of young people to HIV/AIDS continues to be a serious concern in South Africa. HIV transmission largely occurs through heterosexual intercourse in South Africa and portions of the youth population continue to engage in sexual behaviors that place them at risk of HIV infection (Shisana, 2009; Fraser-Hurt et al., 2011). Risk perceptions are a central component of many models of health behavior (for a recent review, Aiken et al., 2012). These models give rise to the behavior motivation hypothesis, or the prediction that individuals who perceive themselves to be at risk of a disease will engage in behaviors known to prevent the disease (Brewer et al., 2004). Numerous studies of disease have tested the behavior motivation hypothesis; fewer studies have tested the risk reappraisal hypothesis, or the prediction that taking an action believed to reduce risk of a disease will lower self-perceived risk for the disease (Brewer et al., 2004). Research to date (to the best of our knowledge) has not specifically considered whether the HIV risk perceptions of South African youth change over time and if they do, what factors are associated with change. This study uses data from the Cape Area Panel Study (CAPS), a longitudinal study of youth and their households from Cape Town, South Africa, to examine whether HIV risk perceptions change over a four-year period and whether sexual behaviors, knowing someone with HIV, race and gender are associated with any change.1.1. HIV Risk PerceptionsA number of studies have found that young South Africans often perceive their risk of HIV infection to be low, even if they engage in sexual risk behaviors (Macintyre et al., 2004; Anderson et al., 2007; Kenyon et al., 2010a; Fraser-Hurt et al., 2011), which may reflect youthful optimism and feelings of invulnerability (Moore and Rosenthal, 1991; Macintyre et al., 2004). (For studies finding that young South Africans have at least moderate levels of knowledge about the sexual transmission of HIV, (Anderson and Beutel, 2007; Shisana, 2009; Fraser- Hurt et al. …

Due to tradeoffs between mating and parental effort, men who pay child support to children from previous unions should be less likely to have subsequent children or to remarry than men who do not pay child support. I evaluate this prediction using data from the Panel Study of Income Dynamics (PSID), a nationally representative sample of American households. As predicted, child support payment is associated with lower probability of subsequent birth. However, the prediction was not met for marriage: men who paid child support were more, rather than less, likely to remarry. One interpretation of this result is that child support payment is an honest signal of men's willingness to commit to parental investment: by continuing to pay child support, men signal to prospective mates that they are good investors. Child support may thus function to some extent as mating effort, by attracting subsequent long-term mates.

Life history theory predicts that greater extrinsic mortality will lead to earlier and higher fertility. To test this prediction, I examine the relationship between life expectancy at birth and several proxies for life history traits (ages at first sex and first marriage, total fertility rate, and ideal number of children), measured for both men and women. Data on sexual behaviors come from the Demographic and Health Surveys (DHS). Two separate samples are analyzed: a cross-sectional sample of 62 countries and a panel sample that includes multiple cross-sectional panels from 48 countries. Multivariate regression analysis is used to control for potential confounding variables. The results provide only partial support for the predictions, with greater support among women than men. However, the prediction is not supported in sub-Saharan African countries, most likely owing to the nonequilibrium conditions observed in sub-Saharan Africa with respect to life expectancy. The applicability of the model to understanding HIV/AIDS risk behaviors is discussed.

Educational expectations, in particular the relationship between race/ ethnicity and educational expectations, have been understudied in less developed countries. We use data from the Cape Area Panel Study (CAPS) to examine the educational expectations of black (African), coloured (mixed race), and white (European ancestry) youth in Cape Town, South Africa. The educational expectations of all three racial groups are high, although coloured youth are less likely than black and white youth to expect to complete postsecondary or postgraduate schooling. Supporting research on educational expectations in the United States and other more developed countries, our findings indicate that socioeconomic status and academic performance matter for educational expectations in South Africa, although their importance varies by racial group. In contrast to U.S. studies that have found effects of family composition for whites only, we found virtually no effects of family composition on the educational expectations of whites or nonwhites. Our findings suggest possible similarities and differences across social contexts in the processes shaping the educational expectations of youth from disadvantaged groups. Because of their potential to influence educational outcomes, educational expectations have been of considerable interest to sociologists. A great deal of research has examined educational expectations in the United States and other more developed countries (e.g., Buchmann and Dalton 2002; Cheng and Starks 2002; Hao and Bonstead-Bruns 1998; Hauser, Tsai, and Sewell 1983; Looker and Pineo 1983; Marjoribanks 2002; Sewell, Haller, and Portes 1969). Relatively few studies have investigated educational expectations in less developed countries (e.g., Adams, Wasikhongo, and Nahemow 1987; Forste, Heaton, and Haas 2004; Moller 1995; Post 1990), particularly the relationship between race/ethnicity and educational expectations. How educational expectations are formed in parts of the world with social structures that may differ from those in the United States and other more developed countries is not well understood. South Africa presents an ideal location for considering how context may influence educational expectations, as a number of social and economic features distinguish it from the United States and other more developed countries. One is the tremendous economic stratification of the country. Wage inequality in South Africa is among the highest in the world, and unemployment rates are as high as 40% (Burger and Woolard 2005; Kingdon and Knight 2001; Klasen 1997; Leibbrandt, Woolard, and Woolard 2000). As a result, there is tremendous variation in access to educational capital, which may influence educational expectations. second is the nature of racial stratification in South Africa: under apartheid (the policy of extreme racial segregation practiced until the early 1990s), individuals were placed into one of three groups on the basis of race-an advantaged group composed of whites (those of European ancestry), a moderately disadvantaged group consisting of both coloureds (those of mixed race) and Asians (mostly from India), and a severely disadvantaged group made up of blacks (Africans) (e.g., Klasen 1997; Mwabu and Schultz 1996; Thomas 1996). Although de jure discrimination ended with the dismantling of apartheid, racial inequality persists in South Africa (e.g., Burgard and Treiman 2006; Burger and Woolard 2005; Charasse-Pouele" and Fournier 2006; Lestrade-Jefferis 2002). By studying educational expectations in a country with a clearly defined racial status hierarchy, we may improve our understanding of the relationship between race and educational expectations. Third, South Africa provides a different schooling context in which to examine educational expectations. For example, school fees (tuition) are generally charged for school enrollment, even for primary and secondary education. Last, dramatic social changes have occurred in South Africa over the past fifteen years. …

HIV/AIDS knowledge is an important component of HIV/AIDS risk prevention strategies that may influence engagement in high risk behavior. This paper examines HIV/AIDS prevention knowledge among a representative sample of 4,174 youth living in Cape Town, South Africa. Data come from the Cape Area Panel Study (CAPS), and include black, coloured, and white respondents ages 14-22. Using an open-ended question, respondents were asked to name ways people can protect themselves from HIV/AIDS infection. Nearly everyone could name at least one method of preventing HIV infection, and respondents named two methods on average. Condoms, abstinence, and limiting the number of sexual partners/having only one sexual partner were the most frequently named prevention methods. Multivariate analysis was used to analyze correlates of specific forms of HIV/AIDS prevention, as well as the total number of prevention methods named by each respondent. Having had sex, highest grade completed, and race were the most commonly significant correlates across models. Race interaction terms were also significant, suggesting that the significance of HIV/AIDS knowledge correlates varies across racial groups. Overall, the results suggest that more depth of knowledge about HIV/AIDS is needed among South African youth to ensure proper protection from the disease, and that HIV/AIDS education might be more successful if tailored to specific racial/ethnic groups.

Using a sample of men living in Albuquerque, NM, we examined the relationship between paternity confidence and men's investment in children. In humans, men may reduce their investment in a child in two ways: indirectly, by ending their relationship with the child's mother and ceasing to cohabit with the child (e.g., divorce), and directly, by allocating less time and fewer resources to the child. In this article, we tested two hypotheses regarding the effect of paternity confidence on investment in children: (1) men will be more likely to divorce women if they suspect or are sure that they are not the father of their wife's child, and (2) controlling for divorce, men will reduce direct investments in low paternity confidence children relative to high paternity confidence children. The first hypothesis was supported by the data. The second hypothesis was supported for two out of three measures of paternal investment we examined; low paternity confidence reduces the time men spend with a child in a group with other children or adults, and it reduces extensive involvement with the child's educational progress; there was no effect of paternity confidence on the amount of time men spend with children in one-on-one interactions. We also examined the effects of unstated paternity confidence (e.g., when men decline to answer the question) on divorce and paternal investment. Overall, the results suggested that paternity confidence plays an important role in shaping men's relationships with women and with their putative genetic children.

A substantial theoretical and empirical literature suggests that stressful events in childhood influence the timing and patterning of subsequent sexual and reproductive behaviors. Stressful childhood environments have been predicted to produce a life history strategy in which adults are oriented more toward short-term mating behaviors and less toward behaviors consistent with longevity. This article tests the hypothesis that adverse childhood environment will predict adult outcomes in two areas: risky sexual behavior (engagement in sexual risk behavior or having taken an HIV test) and marital status (currently married vs. never married, divorced, or a member of an unmarried couple). Data come from the Behavioral Risk Factor Surveillance System. The sample contains 17,530 men and 23,978 women aged 18–54 years living in 13 U.S. states plus the District of Columbia. Adverse childhood environment is assessed through 11 retrospective measures of childhood environment, including having grown up with someone who was depressed or mentally ill, who was an alcoholic, who used or abused drugs, or who served time in prison; whether one’s parents divorced in childhood; and two scales measuring childhood exposure to violence and to sexual trauma. The results indicate that adverse childhood environment is associated with increased likelihood of engaging in sexual risk behaviors or taking an HIV test, and increased likelihood of being in an unmarried couple or divorced/separated, for both men and women. The predictions are supported by the data, lending further support to the hypothesis that childhood environments influence adult reproductive strategy.

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.

We present a biosocial model of human male parental care that allows male parental allocations to be influenced not only by changes in the fitness (welfare) of the recipient offspring, but also by their effects on the man's relationship with the child's mother. The model recognizes four classes of relationships between males and the children they parent: genetic offspring of current mates (combined relationship and parental effort), genetic offspring of previous mates (parental effort solely), step offspring of current mates (relationship effort solely), and stepchildren of previous mates (essentially no expected investment). We test the model using data on parental investments collected from adult males living in Albuquerque, New Mexico, U.S.A. Four measures of paternal investment are examined: the probability that a child attends college (2,191 offspring), the probability that a child who attends college receives money for it ( N = 1,212), current financial expenditures on children ( N = 635), and the amount of time per week that men spend with children ages 5 to 12 years ( N = 2,589). The tests are consistent with a role for relationship effort in parental care: men invest more in the children of their current mates, even when coresidence with offspring is not a confounder.

Life history theory postulates tradeoffs of current versus future reproduction; in both developed and developing nations today, women face evolutionarily novel versions of these tradeoffs. Here we use a nonlinear dynamic model to explore: [1] the general issues of tradeoffs of education, work, and current fertility; [2] some specific examples (e.g., what increase in fertility will compensate for particular delays of age at first birth under given conditions). Finally, we model a largely unrecognized issue. Demographic transitions of the past have been characterized by decreases in fertility accompanied by (sometimes quite large) increases in per capita investment in offspring. The Rio Conference and its followup highlighted the conflicts between low-fertility, high-consumption, versus highfertility, lower consumption strategies — yet we have few ways to make testable predictions about future conflicts. We explore outcomes when impending resource constraints differentially affect short-generation-time-strategists, versus delayed-reproduction-resource-acquirers. The conditions favoring delayed fertility with resource accumulation are highly constrained; under almost all conditions reproduction in the early 20s leads to the greatest lineage success for women in the models.

This paper draws on evolutionary life history theory to examine nonmarital births in the context of women’s ability to secure male parental investment for their offspring. While nonmarital births are usually defined with respect to marital status the day of parturition, we adopt a more nuanced approach that corresponds to men’s willingness to commit to family obligations. Our approach distinguishes between marriages preceding pregnancy, marriages occurring between pregnancy and birth, marriages immediately following birth, and births that are not followed by marriage to the child’s father. Using retrospective marital and reproductive histories from the Panel Study of Income Dynamics (PSID), we observe a range in women’s life history outcomes (fertility and marital measure) corresponding to this range in male commitment around the time of first birth. Self-selection biases are not examined in this analysis, although their implications are discussed.

Life history theory postulates tradeoffs of current versus future reproduction; today women face evolutionarily novel versions of these tradeoffs. Optimal age at first birth is the result of tradeoffs in fertility and mortality; ceteris paribus, early reproduction is advantageous. Yet modern women in developed nations experience relatively late first births; they appear to be trading off socioeconomic status and the paths to raised SES, education and work, against early fertility. Here, [1] using delineating parameter values drawn from data in the literature, we model these tradeoffs to determine how much socioeconomic advantage will compensate for delayed first births and lower lifetime fertility; and [2] we examine the effects of work and education on women's lifetime and age-specific fertility using data from seven cohorts in the Panel Study of Income Dynamics (PSID).

The large human brain, the long period of juvenile dependence, long life span, and male support of reproduction are the co-evolutionary result of the human niche based on skill-in- tensive techniques of resource accrual. The regulation of fertility under traditional conditions is based upon a co-evolved psychology and physiology where adjustments of investment in offspring depend upon the returns to skill and mortality hazards. When all wealth is somatic, the hormonal system controlling ovulation and implantation translates income into genetic descendants. In modern society the existence of extra-somatic wealth is a critical condition to which our evolved proximate physio- logical mechanisms do not respond. However, psychological mechanisms regulating parental in- vestment in offspring quality may lead to greater and greater investment in own and offspring education, a smaller desired family size, a delay in the onset of reproduction, and a reduction in the total numbers of offspring produced. This delay in reproduction can cause many individuals to pro- duce fewer children than desired because fecundity falls during the reproductive part of the life course. As more individuals in a society follow this pattern, more will fail to reach their desired family size. At the same time the effective use of birth control decreases the numbers of families producing more children than desired. Below replacement fertility can result. Predictions from this model were tested using data from the National Survey of Families and Households and the Albuquerque Men study. Am. J. Hum. Biol. 14:233-256, 2002. 2002 Wiley-Liss, Inc