Del Giudice's explication of sex-specific patterns of insecure attachment substantively advances our understanding of attachment organization across development and its role in shaping adult reproductive strategies. An important strength of the model is the incorporation of parental investment and sexual selection theory into current life history models, enabling a better account of sex-differentiated life histories. The focus on sex-specific reorganization of attachment patterns in middle childhood as a critical phase in the formation of reproductive strategies is a novel and exciting idea that should stimulate future research.

Despite these strengths, the synthesis of life history theory and sexual selection theory needs further development. A comprehensive model must incorporate not only the concept of asymmetries in parental investment between the sexes, but also the alternative reproductive strategies that arise within each sex as a result of intrasexual competition. Current sexual selection models, such as Gangestad and Simpson's Strategic Pluralism Theory (2000), emphasize social and sexual competition as important factors shaping adaptive variation in reproductive strategies.

The incorporation of ideas from sexual selection theory into life history models should be especially valuable because the weakness of one theory is often the strength of the other. For instance, life history theory has provided the basis for a useful set of models for explaining development of variation in women's reproductive strategies (e.g., explaining developmental trade-offs between current vs. future reproduction; see Belsky et al. Reference Belsky, Steinberg and Draper1991; Ellis Reference Ellis2004). However, because life history models have not adequately addressed social-sexual competition for mates, they have been limited in their ability to explain strategic variation among men. Sexual selection models, by contrast, have been successful in explaining how males apportion reproductive effort to mating versus parenting in relation to current levels of social-sexual competitiveness (e.g., Gangestad & Simpson Reference Gangestad and Simpson2000; Gross Reference Gross1996), but do not provide an adequate developmental model for how and when males should make these adaptive shifts.

To address these limitations, we have constructed a more comprehensive theoretical framework based on the strengths of each model (Jackson & Ellis, submitted; Jackson et al., submitted). Our approach toward this synthesis has been to integrate the components of social and sexual competition into the developmental trajectories laid out by life history theorists. Our theory and research in this area focus on how early familial environments and status obtained in adolescence and early adulthood contribute, additively and in interaction, to the development of reproductive strategies in men and women.

Because males and females must solve qualitatively different adaptive problems when negotiating life history trade-offs, there should be important sex differences in the tracking of environmental information, or at least the weight given to specific environmental cues (see Gangestad & Simpson Reference Gangestad and Simpson2000; Thiessen Reference Thiessen1994). Females are ultimately constrained by the resources that they can extract from the environment, their relatives, and their mates in order to successfully produce and rear offspring; accordingly, they should be especially attuned to the nature of the local ecology and support in and around their home environments, per life history models. Males, on the other hand, are ultimately constrained by their ability to access, attract, and retain females; accordingly, their own reproductive strategies should be especially attuned to the demands and desires of females and their ability to successfully engage in intrasexual competition, per sexual selection models.

Recent empirical studies lend support to these claims. In a longitudinal study on adolescent development, Ellis and Garber (Reference Ellis and Garber2000) found that early psychosocial stress (i.e., discordant family relationships, father absence/stepfather presence) predicted early pubertal maturation among girls. In the same sample, Jackson et al. (submitted) examined the effects of early psychosocial stress within the home and competency within the peer group on attachment orientation and sexual behavior in late adolescence. As in the previous analyses of pubertal timing, in females, but not in males, early psychosocial stress was a reliable predictor of heightened sexual activity, risky forms of sexual behavior, and avoidant romantic attachment patterns. By contrast, in males, but not females, self-perceived social competence and athletic ability during adolescence were reliable predictors of heightened sexual activity and secure romantic attachment in late adolescence. Thus, consistent with our model, development of female reproductive strategies was more closely linked to variation in familial and ecological conditions, whereas development of male reproductive strategies was more closely linked to social-competitive ability and status.

All children do not respond equally, however, to family environments and social-sexual competition. An important factor noted in section 6.4, but not explicitly modeled by Del Giudice, is that the effects of attachment on social and reproductive strategies may depend on the phenotype of the developing child. Phenotypic characteristics likely moderate the developmental pathways presented by Del Giudice in the following ways. Among females, phenotypic quality could alter the extent to which they are able to extract resources from relatives and mates, moderating in part the relationship between extrinsic risk, attachment orientation, and sexual behavior in adulthood. Among males, phenotypic quality could alter the extent to which they are able to enact specific competitive and reproductive strategies. For instance, the male avoidant strategy detailed by Del Giudice includes a personality profile of inflated self-esteem, self-reliance, and aggression that facilitates status seeking. Although we agree that these traits may aid in intrasexual competition in certain social niches, it is likely that only those males who possess the physical prowess needed to successfully compete in such a manner would benefit from the strategy. Along these lines, Figueredo and Jacobs (Reference Figueredo and Jacobs2000) have argued for a kind of reactive heritability model whereby the inheritance of strategically relevant traits biases individuals toward different strategies. They contend that, “psychosexual development involves a self-assessment of sociosexual capabilities and opportunities, calibrating optimal utilization of physical assets such as size, strength, health, and attractiveness, as well as psychosocial assets such as intelligence, self-efficacy, social skills, personality, and socioeconomic status and/or prospects” (p. 603). In sum, extant phenotypic characteristics should interact with social status and developmental experience to determine life history strategies.

In conclusion, Del Giudice's ideas concerning the sex-specific organization of attachment beginning in middle childhood are likely to assume an important role in research on development of life history strategies. We see Del Giudice's model, together with our own, as affording meaningful steps toward the integration of life history and sexual selection models of human reproductive strategies.