James S. Chisholm

The evolutionary ecology of attachment organization.

Life history theory’s principle of allocation suggests that because immature organisms cannot expend reproductive effort, the major trade-off facing juveniles will be the one between survival, on one hand, and growth and development, on the other. As a consequence, infants and children might be expected to possess psychobiological mechanisms for optimizing this trade-off. The main argument of this paper is that the attachment process serves this function and that individual differences in attachment organization (secure, insecure, and possibly others) may represent facultative adaptations to conditions of risk and uncertainty that were probably recurrent in the environment of human evolutionary adaptedness.

Early Stress Predicts Age at Menarche and First Birth, Adult Attachment, and Expected Lifespan

Life history theory suggests that in risky and uncertain environments the optimal reproductive strategy is to reproduce early in order to maximize the probability of leaving any descendants at all. The fact that early menarche facilitates early reproduction provides an adaptationist rationale for our first two hypotheses: that women who experience more risky and uncertain environments early in life would have (1) earlier menarche and (2) earlier first births than women who experience less stress at an early age. Attachment theory and research provide the rationale for our second two hypotheses: that the subjective early experience of risky and uncertain environments (insecurity) is (3) part of an evolved mechanism for entraining alternative reproductive strategies contingent on environmental risk and uncertainty and (4) reflected in expected lifespan. Evidence from our pilot study of 100 women attending antenatal clinics at a large metropolitan hospital is consistent with all four hypotheses: Women reporting more troubled family relations early in life had earlier menarche, earlier first birth, were more likely to identify with insecure adult attachment styles, and expected shorter lifespans. Multivariate analyses show that early stress directly affected age at menarche and first birth, affected adult attachment in interaction with expected lifespan, but had no effect on expected lifespan, where its original effect was taken over by interactions between age at menarche and adult attachment as well as age at first birth and adult attachment. We discuss our results in terms of the need to combine evolutionary and developmental perspectives and the relation between early stress in general and father absence in particular.

Attachment and time preference

This paper investigates hypotheses drawn from two sources: (1) Belsky, Steinberg, and Draper’s (1991) attachment theory model of the development of reproductive strategies, and (2) recent life history models and comparative data suggesting that environmental risk and uncertainty may be potent determinants of the optimal tradeoff between current and future reproduction. A retrospective, self-report study of 136 American university women aged 19–25 showed that current recollections of early stress (environmental risk and uncertainty) were related to individual differences in adult time preference and adult sexual behavior, and that individual differences in time preference were related to adult attachment organization and sexual behavior. These results are consistent with the hypothesis that perceptions of early stress index environmental risk and uncertainty and mediate the attachment process and the development of reproductive strategies. On this view individual differences in time preference are considered to be part of the attachment theoretical construct of an internal working model, which itself is conceived as an evolved algorithm for the contingent development of alternative reproductive strategies.

Evolutionary perspectives on pregnancy: maternal age at menarche and infant birth weight

We present a novel evolutionary analysis of low birth weight (LBW). LBW is a well-known risk factor for increased infant morbidity and mortality. Its causes, however, remain obscure and there is a vital need for new approaches. Life history theory, the most dynamic branch of evolutionary ecology, provides important insights into the potential role of LBW in human reproductive strategies. Life history theorys primary rationale for LBW is the trade-off between current and future reproduction. This trade-off underlies the prediction that under conditions of environmental risk and uncertainty (experienced subjectively as psychosocial stress) it can be evolutionarily adaptive to reproduce at a young age. One component of early reproduction is early menarche. Early reproduction tends to maximise offspring quantity, but parental investment theorys assumption of a quantity-quality trade-off holds that maximizing offspring quantity reduces quality, of which LBW may be the major component. We therefore predict that women who experienced early psychosocial stress and had early menarche are more likely to produce LBW babies. Furthermore, the extension of parent-offspring conflict theory in utero suggests that the fetus will attempt to resist its mothers efforts to reduce its resources, allocating more of what it does receive to the placenta in order to extract more maternal resources to increase its own quality. We propose that LBW babies born to mothers who experience early psychosocial stress and have early menarche are more likely to have a higher placental/fetal weight ratio. We review evidence in support of these hypotheses and discuss the implications for public health.

Reproductive development and parental investment during pregnancy: moderating influence of mother's early environment.

The association between a womans age at menarche and the birth weight of her children is highly variable across human populations. Life history theory proposes that a womans early environment may moderate this association and thus account for some of the variation between populations. According to one life history theory model, for individuals who develop in a childhood environment of high local mortality rates (experienced subjectively as psychosocial stress), it can be adaptive to mature earlier, have more offspring during their reproductive lifetime, and reduce investment in each offspring. In an environment of low psychosocial stress, however, it may be adaptive to mature later, have fewer offspring, and invest more in each. In this study, birth weight and proportionate birth weight (neonates birth weight as a percentage of its mothers prepregnancy weight) were used as measures of parental investment during pregnancy. In a sample of 580 first‐time mothers, we tested the hypothesis that the psychosocial stress experienced as a child would moderate the association between age at menarche and investment during pregnancy. We found that earlier menarche in those women who experienced stressful life events before 15 years of age was associated with a lower birth weight and proportionate birth weight. Conversely, in those who reported no childhood stressors, earlier menarche was associated with increased birth weight and proportionate birth weight. Our data suggest that the moderating influence of the childhood psychosocial environment on the association between age at menarche and parental investment throughout gestation operates in a dose‐dependent manner. Am. J. Hum. Biol., 2010.

Attachment and Cooperation in Religious Groups An Example of a Mechanism for Cultural Group Selection

Bowlby proposed that “the psychological problem of ensuring persistent co‐operative behaviour” in groups was solved by emotional valuation of the group leader, group policy, or the group itself derived from the infant‐mother attachment relationship. He described how an emotionally valued relationship with a group leader, which is rooted in early attachments, can motivate an individual to cooperate for the benefit of the group. Bowlby’s insights, studies of attachment relationships with a deity, and the application of multilevel and group selection to cooperation in religious groups together show how attachment to a deity (supernatural agent) could be a mechanism for intragroup cooperation, including the within‐group cooperation required for group selection. As such, it links the attachment system, a pillar of human relationships and personality, to cooperation in groups. We also consider how the attachment system could be a basis for intragroup cooperation generally and compare this possibility to two other theories about human social cooperation, the “tribal social instincts” hypothesis and the evolution of “shared intentionality.”

Early psychosocial stress affects men's relationship length

Life history theory predicts that the optimal reproductive strategy for individuals in risky and uncertain environments (subjectively experienced as early psychosocial stress) is to maximize current reproduction to minimize the chances of lineage extinction. Having many short-term relationships and many lifetime sex partners are ways to maximize current reproduction, but they come at a cost (e.g., decreased resources for future reproduction, decreased desirability as a future mate, etc.). This study, therefore, examined whether sexually active individuals with high levels of early psychosocial stress report more terminated short-term relationships, a shorter relationship length with their current partner, and more lifetime sex partners than those with less early psychosocial stress. Early psychosocial stress in men was associated with more terminated short-term relationships and a greater number of lifetime sex partners, but not with current relationship length; in women, high early psychosocial stress was associated with shorter current relationship length but not with the number of terminated short-term relationships or number of lifetime sex partners. Results are discussed from the perspective of life history theory and gender differences in preferences for short- and long-term relationships.

Early Psychosocial Stress Predicts Extra-Pair Copulations

Cheating on a mate, known as an extra-pair copulation (EPC), is considered unacceptable by most individuals. Nonetheless many individuals engage in such risky behaviors. Because individuals with high, as opposed to low, levels of early psychosocial stress are more risk prone and more likely to engage in opportunistic matings, we predicted that individuals reporting EPCs, one of many types of opportunistic mating (e.g., one-night stand, consecutive short-term relationships etc), have higher levels of early psychosocial stress than those who do not. Two types of EPCs were examined: EPC-self (EPC-S), having sex with someone other than ones mate, and EPC-other (EPC-O), having sex with someone elses mate. In a sample of 229 women and 161 men, significantly higher levels of early psychosocial stress were found amongst those reporting an EPC-S than those reporting none, irrespective of EPC-Os. Furthermore, the more EPC-Ss men, but not women, reported the higher their early psychosocial stress. Early psychosocial stress was not associated with EPC-Os irrespective of EPC-Ss. Participants were also classified into one of four groups (no EPCs, EPC-O only, EPC-S only, or EPC-S&O) which significantly interacted with early psychosocial stress. Results are discussed from adaptationist and mechanist perspectives and why early psychosocial stress was higher in individuals reporting EPC-Ss irrespective of EPC-Os, but not EPC-Os irrespective of EPC-Ss, than those not reporting the EPC of interest.

On Religion: A Reply to Anderson

We welcome Anderson’s (2010) encouraging comments and are grateful for his attention to the definition and evolution of religion. We have much agreement with him. Please note that the primary target of our original paper was cooperation within human groups, with religious groups as an example of a group, rather than religion per se. Here, however, we follow Anderson’s lead and focus on religion itself. Our paper did provide James’s (1961 [1902]) working definition of religion from the Gifford Lectures around relationship with the divine (Weingarten and Chisholm 2009: 762). This is often a useful working definition, especially in psychology of religion, and apropos to many aspects of our paper such as attachment relationships with a deity. However, for lack of space we did not describe James’s, or others’, discussions of the complex nature of religion and its definitions. Thus, Anderson’s discussion of definitions of religion, including his own, is very useful. An excellent collection of definitions is also in Kunin (2006). We also agree with Anderson’s comment to reject simple evolutionary explanations such as “the God gene” but, instead, “to explain how each component [of religion] evolved and then how they have come to be assembled in the various ways ethnographers have documented” (Anderson 2010:421). The multifaceted nature of religious phenomena calls for multifaceted evolutionary understandings, such as from authors cited in our paper, from Alcorta to Winkelman and others like Bloch (2008) and Mithen (1996). Further, genes are not always necessary for evolution (e.g., cultural evolution), nor are they sufficient, for selection operates on phenotypes, not genotypes, and development of phenotypes must be addressed. Thus, we have always viewed that the attachment system would be but one of many mechanisms underlying tremendous varieties of religious phenomena across space and time. To further address the definition and evolution of religion, we begin with Anderson’s second point: “‘religion’ is a Western concept, and most societies worldwide (especially the