Life history theory and human reproductive behavior

Creating shared goals and experiences as a pathway to peace

Glowacki offers many new directions for understanding and even eliminating the problem of war, especially creating positive interdependencies with out-group members. We develop Glowacki's intriguing proposition that in-group dynamics provide a route to peace by describing a prosocial motivational system, the caregiving system, that aligns individual interests and eliminates the need to use coercion to achieve mutually beneficial outcomes.

No evidence for a relationship between MHC heterozygosity and life history strategy in a sample of North American undergraduates

Although allelic diversity at the major histocompatibility complex (MHC) has implications for adaptive immunity, mate choice, and social signalling, how diversity at the MHC influences the calibration of life history strategies remains largely uninvestigated. The current study investigated whether greater MHC heterozygosity was associated with markers of slower life history strategies in a sample of 789 North American undergraduates. Contrary to preregistered predictions and to previously published findings, MHC heterozygosity was not related to any of the psychological life history-relevant variables measured (including short- vs. long-term sexual strategy, temporal discounting, the Arizona life history battery, past and current health, disgust sensitivity, and Big Five personality traits). Further, no meaningful effects emerged when analysing women and men separately. Possible reasons for why the current results are inconsistent with previous work are discussed.

Poverty and Puberty: A Neurocognitive Study of Inhibitory Control in the Transition to Adolescence

Pubertal development during early adolescence is modestly associated with individual differences in slowly developing inhibitory control of impulses-an aspect of self-regulation associated with reward-seeking behaviors such as the onset and frequency of sexual activity. However, this effect may be much stronger in resource-poor environments. On the basis of life-history and r/K-selection theories, we tested the hypothesis that early pubertal timing would be more strongly associated with less mature neurocognitive inhibitory control in lower-income environments. In an economically diverse Appalachian sample (N = 157; 138 with complete neuroimaging data) of 14-year-olds (52% male), inhibitory control was measured using the multisource-interference task during functional MRI. Results showed that among poor youths only, more advanced puberty for one's age was linked with lower inhibitory control for the neural but not the behavioral measure. This finding has implications regarding poverty, neurocognitive development, and health-risk behaviors in adolescence.

Material security, life history, and moralistic religions: A cross-cultural examination

Researchers have recently proposed that "moralistic" religions-those with moral doctrines, moralistic supernatural punishment, and lower emphasis on ritual-emerged as an effect of greater wealth and material security. One interpretation appeals to life history theory, predicting that individuals with "slow life history" strategies will be more attracted to moralistic traditions as a means to judge those with "fast life history" strategies. As we had reservations about the validity of this application of life history theory, we tested these predictions with a data set consisting of 592 individuals from eight diverse societies. Our sample includes individuals from a wide range of traditions, including world religions such as Buddhism, Hinduism and Christianity, but also local traditions rooted in beliefs in animism, ancestor worship, and worship of spirits associated with nature. We first test for the presence of associations between material security, years of formal education, and reproductive success. Consistent with popular life history predictions, we find evidence that material security and education are associated with reduced reproduction. Building on this, we then test whether or not these demographic factors predict the moral concern, punitiveness, attributed knowledge-breadth, and frequency of ritual devotions towards two deities in each society. Here, we find no reliable evidence of a relationship between number of children, material security, or formal education and the individual-level religious beliefs and behaviors. We conclude with a discussion of why life-history theory is an inadequate interpretation for the emergence of factors typifying the moralistic traditions.

Decomposing environmental unpredictability in forecasting adolescent and young adult development: A two-sample study

To illuminate which features of an unpredictable environment early in life best forecast adolescent and adult functioning, data from two longitudinal studies were examined. After decomposing a composite unpredictability construct found to predict later development, results of both studies revealed that paternal transitions predicted outcomes more consistently and strongly than did residential or occupational changes across the first 5 years of a child's life. These results derive from analyses of the NICHD Study of Early Child Care and Youth Development, which included diverse families from 10 different sites in the United States, and from the Minnesota Longitudinal Study of Risk and Adaptation, whose participants came from one site, were disproportionately economically disadvantaged, and were enrolled 15 years earlier than the NICHD Study sample. The finding that results from both studies are consistent with evolutionary, life history thinking regarding the importance of males in children's lives makes this general, cross-study replication noteworthy.

Stressful family environment, mortality, and child socialisation: Life-history strategies among adolescents and adults from unfavourable social circumstances

This study, based on questionnaires given to 732 subjects, uses an integrative approach with a focus on evolutionary (life-history) explanations. In accordance with Belsky, Steinberg, and Draper’s theoretical model of socialisation (1991), we claim that experiences during childhood trigger variations in the life cycle and shift developmental trajectories as adaptive answers to different environmental conditions. Unfavourable family conditions constitute an unpredictable and unstable environment that make children susceptible to adopting opportunistic mating strategies rather than parenting strategies. Based on Chisholm’s statement (1993) that high stress in the family provides cues for local death rates, we argue that mortality rates may have a significant effect on reproductive decisions, even in post-industrial societies. We report that length of schooling, date of the ” rst marriage, and fertility were associated with the subjects’ family conditions, such as parental affirmation, emotional atmosphere, parent-subject conflicts, and parental relations. Women growing up in unfavourable family circumstances ”nish schooling and marry earlier, and this shift in developmental trajectory is likely to lead to the higher number of children measured among these women. Men, on the other hand, do not show such a difference in reproductive output, which may be due to their increased involvement in sexual competition. Remarkably, significant correlation has been found between life-history strategy and mortality rates; those coming from unfavourable environments have more deceased sisters and brothers than others. It is possible that individual differences in mating and parenting behaviour are still contingent, among others, on local death rates.

The evolutionary context of postnatal depression

"Postnatal depression" denotes the syndrome of dysphoria, debility, and anxiety that follows childbirth in about 10-20% of women (as variously estimated). Its etiology is seen to be lodged in a variety of psychosocial as well as biological factors, among which the isolating and pressured culture of contemporary society (especially for women/mothers) is commonly singled out as a powerful precipitator. This view is extended here through the evolutionary perspective which casts maternal distress as a set of adaptive responses with the function, in ancestral environments, of soliciting support for a mother who feels that her maternal responsiveness may be threatened. As continuous caretaking of the infant is the active expression of evolved maternal responsiveness, departures from this pattern result in anxiety and distress that seek resolution. Manifestations of maternal distress in contemporary society are dysfunctional, however, since the present social structure does not provide spontaneous and immediate support that can spring forth within small, closely knit social units. Furthermore, for present-day mothers distress is self-perpetuating since the ingrained tendency toward continuing responsiveness rarely finds practical expression and is thus converted into anxious vigilance and depression. This view generates the hypothesis that the emotional and cognitive contents of maternal vigilance are associated with the needs of the infant and will therefore be focused on crying and feeding. A number of qualitative studies of women's experiences during the postpartum bear out this prediction and support the feasibility of the evolutionary hypothesis of "postnatal depression" as a set of adaptive responses, now out of place in a novel environment.

Unwanted childbearing and household food insecurity in the United States

Household food insecurity is a population health concern disproportionately affecting families with children in the United States. Unwanted childbearing may place unanticipated strain on families to meet basic needs, heightening the risk for household food insecurity. We investigated the association between mother's and father's report of unwanted childbearing and exposure to household food insecurity among children residing in two-parent households in the United States. Data from the Early Childhood Longitudinal Study - Birth Cohort, a nationally representative cohort of US children (n ∼ 6150), were used to estimate the odds of household food insecurity when children were aged 9 months and 2 years, separately, based on parental report of unwanted childbearing. The majority of children were reported as wanted by both parents (74.4%). Of the sample, report of unwanted childbearing by father-only was 20.0%, mother-only was 3.4% and joint mother and father was 2.2%. Household food insecurity was higher when children were 9 months compared with 2 years. In adjusted models accounting for confounders, children born to mothers and fathers who jointly reported unwanted childbearing were at higher odds of exposure to household food insecurity at 9 months [adjusted odds ratio (AOR) = 3.31; 95% confidence interval (CI): 1.97, 5.57] and 2 years (AOR = 2.52; 95% CI: 1.12, 5.68). In two-parent households, we found that children raised by parents reporting unwanted childbearing were more likely to be exposed to food insecurity and potentially related stressors. Further studies that prospectively measure wantedness before the child's birth will aid in confirming the direction of this association.

Investimento materno e história reprodutiva de mães residentes em contextos com diferentes graus de urbanização

A presente pesquisa tem como objetivo caracterizar o investimento materno e a história reprodutiva de mães que vivem em diferentes contextos. Para tal, 150 mães que residiam em três contextos com diferentes graus de urbanização foram entrevistadas. Por meio da análise estatística dos dados constatou-se que houve diferenças significativas entre os contextos, além de correlações positivas entre os núcleos reprodutivos, como idade da primeira relação sexual e idade da mãe no nascimento do primeiro filho. Conclui-se que as estratégias reprodutivas são influenciadas pela história de vida das mães, das condições sociodemográficas atuais e do contexto onde vivem.

Social Inclusion Facilitates Interest in Mating

According to a life history framework, variability across an organism's lifespan necessitates trade-offs between behaviors that promote survival and those that promote reproduction. Adopting this perspective, the current work investigates how social acceptance or rejection can influence the differential priority placed on mating and survival motivations. Because social acceptance is an important survival-related cue (i.e., group living provides protection from predators and sharing of resources), we predicted that recent experiences of social acceptance should increase people's motivation to mate. In support of this prediction, Study 1 found that participants who were included in an electronic ball-toss game showed more interest in mating (regardless of the potential mate's attractiveness) than excluded and control participants. In Study 2, participants who recalled an experience of social acceptance viewed sexual affiliation as more important than did participants in rejection and control conditions. Collectively, these results suggest an adaptive trade-off such that interest in mating increases upon satiation of affiliative needs. Furthermore, these findings demonstrate that the experience of social acceptance can have unique effects and should not be treated as the sole comparison condition when studying social rejection.

Reproductive strategy, sexual development and attraction to facial characteristics

Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated with reproductive strategies. Stress during early development can retard or accelerate sexual maturation and reproduction. Early age of menarche is associated with absence of younger siblings, absence of a father figure during early life and increased weight. Father absence during early life is also associated with early marriage, pregnancy and divorce. Choice of partner characteristics is critical to successful implementation of sexual strategies. It has been suggested that sexually dimorphic traits (including those evident in the face) signal high-quality immune function and reproductive status. Masculinity in males has also been associated with low investment in mate and offspring. Thus, women's reproductive strategy should be matched to the probability of male investment, hence to male masculinity. Our review leads us to predict associations between the rate of sexual maturation and adult preferences for facial characteristics (enhanced sexual dimorphism and attractiveness). We find for men, engaging in sex at an early age is related to an increased preference for feminized female faces. Similarly, for women, the earlier the age of first sex the greater the preference for masculinity in opposite-sex faces. When we controlled sexual dimorphism in male faces, the speed of sexual development in women was not associated with differences in preference for male facial attractiveness. These developmental influences on partner choice were not mediated by self-rated attractiveness or parental relationships. We conclude that individuals assort in preferences based on the rapidity of their sexual development. Fast developing individuals prefer opposite-sex partners with an increased level of sexually dimorphic facial characteristics.

Why are human newborns so fat? Relationship between fatness and brain size at birth [retracted article]

The plumpness of the human newborn has long been recognized as a trait in need of explanation among researchers. Using a linear regression analysis, we find that head circumference is significantly and positively associated with BMI at birth, after gestational age and birthlength were controlled for, in a sample of 1,069 healthy liveborn routinely delivered at the University Hospital of Coimbra (partial correlation r = 0.409, P < 0.0001). This significant association is consistent with the idea that newborn fatness is related to the higher need of lipids in newborn humans as an energetic and plastic substrate during its accelerated brain growth period. As birthweight and birth head size are associated with head size and cognitive abilities in childhood and adult life, it could be postulated that these cognitive abilities could have acted as selective pressure responsible for the newborn fatness increase in our lineage.

Variation in suicidality among substance-abusing women: the role of childhood adversity

The relationship of early adversity to suicidality in later life has been noted in diverse populations. Here we report such a relationship for a sample of African American women who smoke crack cocaine. This article is a secondary analysis of data from women (mean age = 31 years; range, 19-48) who were recruited from treatment settings (n = 152) or informal community contacts (n = 56). The present analyses focused on measures related to investment in self-preservation and development, particularly suicidal ideation and attempts. Multiple regression analyses were used to model the effect of early stress (sexual abuse, parental loss, and parental impairment) on the primary outcome measures (suicidality total, age at first consensual sexual relations, and years of education). Suicidality was associated with childhood adversity (sexual abuse, loss of mother). Of those who had experienced early sexual abuse, 42% had attempted suicide, compared to 19% of those who had not been sexually abused.

Evolutionary Psychology

Evolutionary psychology (EP) presents a new, integrated approach to human behavior, by explaining how the mental programs, designed by evolutionary selection, guide our social behavior. It claims that cognitive and emotional processes—that is domain-specific algorithms—have been selected in our evolutionary environment as devices of solving particular adaptive problems faced by the Pleistocene hunter-gatherers. Evolutionary psychologists can develop testable explanations that focus on aspects and mechanisms of behavior that cannot readily be explained with current psychological theories. An adaptationist approach provides a powerful explanatory framework that helps us to eliminate the old dichotomies from our thinking, such as innate and learned, universality and diversity, etc. At the same time, however, evolutionary psychology implies several problems and difficulties that should be solved in the future in order to avoid useless confrontations with psychologists. The message of Darwinism to psychology is that the analysis of the evolution of mental capacities and the explanation of the adaptive mechanisms of behavior are crucial contributions to forming an integrated view of ourselves.

Freud: the first evolutionary psychologist?

An evolutionary perspective on attachment theory and psychoanalytic theory brings these two fields together in interesting ways. Application of the evolutionary principle of parent-offspring conflict to attachment theory suggests that attachment styles represent context-sensitive, evolved (adaptive) behaviors. In addition, an emphasis on offspring counter-strategies to adult reproductive strategies leads to consideration of attachment styles as overt manifestations of psychodynamic mediating processes, including the defense mechanisms of repression and reaction formation.

Evolution and proximate expression of human paternal investment

In more than 95% of mammalian species, males provide little direct investment in the well-being of their offspring. Humans are one notable exception to this pattern and, to date, the factors that contributed to the evolution and the proximate expression of human paternal care are unexplained (T. H. Clutton-Brock, 1989). The nature, extent, and influence of human paternal investment on the physical and social well-being of children are reviewed in light of the social and ecological factors that are associated with paternal investment in other species. On the basis of this review, discussion of the evolution and proximate expression of human paternal investment is provided.

Quality of early family relationships and individual differences in the timing of pubertal maturation in girls: a longitudinal test of an evolutionary model

In an 8-year prospective study of 173 girls and their families, the authors tested predictions from J. Belsky, L. Steinberg, and P. Draper's (1991) evolutionary model of individual differences in pubertal timing. This model suggests that more negative-coercive (or less positive-harmonious) family relationships in early childhood provoke earlier reproductive development in adolescence. Consistent with the model, fathers' presence in the home, more time spent by fathers in child care, greater supportiveness in the parental dyad, more father-daughter affection, and more mother-daughter affection, as assessed prior to kindergarten, each predicted later pubertal timing by daughters in 7th grade. The positive dimension of family relationships, rather than the negative dimension, accounted for these relations. In total, the quality of fathers' investment in the family emerged as the most important feature of the proximal family environment relative to daughters' pubertal timing.