This target article presents an integrated evolutionary model of the development of attachment and human reproductive strategies. It is argued that sex differences in attachment emerge in middle childhood, have adaptive significance in both children and adults, and are part of sex-specific life history strategies. Early psychosocial stress and insecure attachment act as cues of environmental risk, and tend to switch development towards reproductive strategies favoring current reproduction and higher mating effort. However, due to sex differences in life history trade-offs between mating and parenting, insecure males tend to adopt avoidant strategies, whereas insecure females tend to adopt anxious/ambivalent strategies, which maximize investment from kin and mates. Females are expected to shift to avoidant patterns when environmental risk is more severe. Avoidant and ambivalent attachment patterns also have different adaptive values for boys and girls, in the context of same-sex competition in the peer group: in particular, the competitive and aggressive traits related to avoidant attachment can be favored as a status-seeking strategy for males. Finally, adrenarche is proposed as the endocrine mechanism underlying the reorganization of attachment in middle childhood, and the implications for the relationship between attachment and sexual development are explored. Sex differences in the development of attachment can be fruitfully integrated within the broader framework of adaptive plasticity in life history strategies, thus contributing to a coherent evolutionary theory of human development.

Evolutionary models of behavior often encounter resistance due to an apparent focus on themes of sex, selfishness, and gender differences. The target article might seem ripe for such criticism. However, life history theory suggests that these themes, and their counterparts, including cooperation, generosity, and gender similarities, represent two sides of the same coin – all are consequences of reproductive trade-offs made throughout development.

In middle childhood, boys show more avoidant attachments and girls more ambivalent attachments as a prelude to gender differentiation in reproductive strategies. However, we have failed to find systematic and method-independent gender differences in middle or late childhood attachments, nor in adult attachment representations. We conclude that Del Giudice's model rests on a brittle empirical basis.

In this commentary, we attempt to broaden thinking and dialogue about how our ancestral past might have affected attachment and reproductive strategies. We highlight the theoretical benefits of formulating specific predictions of how different sources of stress might impact attachment and reproductive strategies differently, and we integrate some of these ideas with another recent evolutionary model of human mating.

Female behavior that is driven by ambivalent attachment is far from passive or withdrawn. As dramatised in the movie “Fatal Attraction,” such women's emotional hyper-reactivity is often expressed in violence, which is antithetical to securing investment from mates or peers. Single motherhood, rather than reflecting an avoidant strategy in which close relationships are devalued, is often the result of ecological conditions in which paternal investment is desired but unavailable.

This commentary cites evidence to argue that girls growing up in a competitive and aggressive environment are more likely to shift to avoidant attachment than to ambivalent attachment in middle childhood. These avoidant women are also more likely to favor a short-term mating strategy. The role of oxytocin (OT) and early experience in shaping an avoidant attachment in females is also discussed.

Del Giudice addresses a complex and pertinent theoretical issue: the evolutionary adaptiveness of sex differences in attachment styles in relation to life history strategy. Although we applaud Del Giudice for calling attention to the problem, we regret that he does not sufficiently specify how attachment styles serve as an integral part of a coordinate life history strategy for either sex.

An extended period of childhood and juvenility is a distinctive aspect of human life history. This stage appears to be important for learning cultural, social, and ecological skills that help prepare the child for the adult socio-competitive environment. The unusual pattern of adrenarche in humans (and chimpanzees) may facilitate adaptive modification of the neurobiological mechanisms that underpin reproductive strategies. Longitudinal monitoring of DHEA/S in naturalistic context could provide important new insights into these aspects of child development.

We propose that middle childhood female ambivalent attachment, given the adaptive problem of uncertainty of future investment, is designed to evoke immediate investment from current caregivers, rather than new investment sources. We suggest greater specificity of strategic attachment solutions to adaptive problems that differ by sex, time, and relationship type.

According to evolutionary, genetic, and endocrinal perspectives, gender differences are modulated by the interaction between intra-uterine stress, genetic equipments, and the availability of the facilitating environment during the newborn period. The social message of fitness over obstacles during socialization and the discussion of secure/non-secure attachment styles should take into consideration the brain functions, which are altered differently in response to intra- and extra-uterine stress in each gender.

The problem with elaborations of attachment theory is attachment theory itself. How would a mind that works the way the theory posits have increased its owner's fitness in hunter-gatherer times? The child's mind is more capacious and discerning than attachment theorists give it credit for. Early-appearing, long-lasting personality characteristics, often mistaken for the lingering effects of early experiences, are more likely due to genetic influences on personality.

The mechanism proposed by Del Giudice by which adult attachment style is adapted to the extrinsic risk in the local environment via attachment style during the early years does not fulfill important criteria of an adaptation. The proposed mechanism is neither specific, nor developmentally reliable, nor effective. Therefore, it should not be considered an adaptation.

Del Giudice's model of sex-specific attachment patterns demonstrates the usefulness of infusing life history theory with principles of sexual selection. We believe a full synthesis between the two theories provides a foundation for a comprehensive model of alternative reproductive strategies. We extend Del Giudice's ideas based on our own program of research, focusing specifically on the importance of intrasexual competition and the individual phenotype during development.

This commentary explores the reproductive strategies and attachment patterns among homeless youths. Del Giudice's integrated evolutionary model is applied to a homeless youth population that must function in ecological settings of constant high risk and stress. Different reproductive needs result in different patterns of high-risk behaviors. Intervention considering the sex differences, life history, and early caregiver–child relationships is suggested.

The target article proposes a model to explain the emergence of sex differences in attachment in middle childhood and their implications for reproductive strategies. While biological factors are prominent in the model, little is said about the social context of middle childhood and its contributions. There is also a need to clarify the fundamental nature of attachment in middle childhood.

Evolutionary Life History Theory (LHT) is a powerful framework that can be used for understanding behavioral strategies as contingent adaptations to environmental conditions. Del Giudice uses LHT as a foundation for describing the attachment process as an evolved psychological system which evaluates life conditions and chooses reproductive strategies appropriate in the developmental environment, integrating findings across several literatures.

Del Giudice provides an extension of the life history theory of attachment that incorporates emerging data suggestive of sex differences in avoidant male and preoccupied female attachment patterns emerging in middle childhood. This commentary considers the place of disorganized attachment within this theory and why male children may be more prone to disorganized attachment by drawing on Trivers's parental investment theory.

Our research in China does not show gender differences in insecure attachment patterns. We believe that cultural differences between Chinese and Western societies may help to explain this phenomenon. Mating and parenting circumstances in China do not allow males to adopt a zero-investment strategy. In addition, attachment styles are transmitted across generations and last for the whole lifespan. Here, we argue that the influence of mating and parenting on the well-developed attachment patterns in childhood is relatively small.

Research with nonhuman primates can make important contributions to life history models of human attachment and reproductive strategies, such as: including parental responsiveness into female reproductive strategies, testing the assumption that adult attachment is a reproductive adaptation, assessing genetic and environmental effects on attachment and reproduction, and investigating the mechanisms through which early stress results in accelerated reproductive maturation.

Del Giudice's model belongs among those that highlight the role of adaptive developmental plasticity in human reproductive strategies; but at least three other forms of evolutionary adaptation also influence reproductive behavior. Similar to earlier models, the existing evidence suggests that Del Giudice's hypothesized effects are rather weak. In particular, adult attachment styles are hardly predictive of outcomes visible to natural selection.