The current paper synthesizes theory and data from the field of life history (LH) evolution to advance a new developmental theory of variation in human LH strategies. The theory posits that clusters of correlated LH traits (e.g., timing of puberty, age at sexual debut and first birth, parental investment strategies) lie on a slow-to-fast continuum; that harshness (externally caused levels of morbidity-mortality) and unpredictability (spatial-temporal variation in harshness) are the most fundamental environmental influences on the evolution and development of LH (...) strategies; and that these influences depend on population densities and related levels of intraspecific competition and resource scarcity, on age schedules of mortality, on the sensitivity of morbidity-mortality to the organism’s resource-allocation decisions, and on the extent to which environmental fluctuations affect individuals versus populations over short versus long timescales. These interrelated factors operate at evolutionary and developmental levels and should be distinguished because they exert distinctive effects on LH traits and are hierarchically operative in terms of primacy of influence. Although converging lines of evidence support core assumptions of the theory, many questions remain unanswered. This review demonstrates the value of applying a multilevel evolutionary-developmental approach to the analysis of a central feature of human phenotypic variation: LH strategy. (shrink)

The National Longitudinal Study of Adolescent Health data were used to test predictions from life history theory. We hypothesized that (1) in young adulthood an emerging life history strategy would exist as a common factor underlying many life history traits (e.g., health, relationship stability, economic success), (2) both environmental harshness and unpredictability would account for unique variance in expression of adolescent and young adult life history strategies, and (3) adolescent life history traits would predict young adult life history strategy. These (...) predictions were supported. The current findings suggest that the environmental parameters of harshness and unpredictability have concurrent effects on life history development in adolescence, as well as longitudinal effects into young adulthood. In addition, life history traits appear to be stable across developmental time from adolescence into young adulthood. (shrink)

We present a psychometric test of life history theory as applied to human individual differences using MIDUS survey data (Brim et al. 2000). Twenty scales measuring cognitive and behavioral dimensions theoretically related to life history strategy were constructed using items from the MIDUS survey. These scales were used to construct a single common factor, the K-factor, which accounted for 70% of the reliable variance. The scales used included measures of personal, familial, and social function. A second common factor, Covitality, was (...) constructed from scales for physical and mental health. Finally, a single general factor, Personality, was constructed from scales for the “Big Five” factors of personality. The K-factor, covitality factor, and general personality factor correlated significantly with each other, supporting the prediction that high K predicts high somatic effort and also manifests in behavioral display. Thus, a single higher-order common factor, the Super-K factor, was constructed that consisted of the K-factor, covitality factor, and personality factor. (shrink)

A secondary analysis was performed on preliminary data from an ongoing cross-cultural study on assortative pairing. Independently sampled pairs of opposite-sex romantic partners and of same-sex friends rated themselves and each other on Life History (LH) strategy and mate value. Data were collected in local bars, clubs, coffeehouses, and other public places from three different cultures: Tucson, Arizona; Hermosillo, Sonora; and San José, Costa Rica. The present analysis found that slow LH individuals assortatively pair with both sexual and social partners (...) more strongly than fast LH individuals. We interpret this phenomenon as representing (1) an adaptation for preserving coadapted genomes in slow LH strategists to maintain high copying fidelity genetic replication while producing a lower number of offspring in stable, predictable, and controllable environments and (2) a bet-hedging adaptation in fast LH strategists, favoring the genetic diversification of a higher number of offspring in unstable, unpredictable, and uncontrollable environments. (shrink)

Our commentary articulates some of the commonalities between Baumeister et al.'s theory of socially differentiated roles and Strategic Differentiation-Integration Effort. We expand upon the target article's position by arguing that differentiating social roles is contextual and driven by varying ecological pressures, producing character displacement not only among individuals within complex societies, but also across social systems and multiple levels of organization.

The “straw man” prior expectation of the dominant social psychology paradigm is that humans should behave with perfect rationality and high ethical standards. The more modest claim of evolutionary psychologists is that humans have evolved specific adaptations for adaptive problems that were reliably present in the ancestral environment. Outside that restricted range of problems, one should not expect optimal behavior.

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.

Many now consider “instinct” and “learning” opposite poles of a unidimensional continuum. An alternative model with two independently varying parameters predicts different selective pressures. Behavioral adaptation matches the organism's utilizations of stimuli and responses to their ecological validities: the mean validity over evolutionary time specifies the optimal initial potency of the prepared association; the variance specifies the optimal prepared plasticity.

It is anthropomorphic to speak of Nature designing adaptations for a specific function, as if with conscious intent. Any effect constitutes an adaptive function if it contributes to survival and to reproduction. Natural selection is blind to what might have been the original function. Mutations arise by purest accident and are selected based on whatever fortuitous effects they might produce.

Fincher & Thornhill (F&T) present a compelling argument that parasite stress underlies certain cultural practices promoting assortative sociality. However, we suggest that the theoretical framework proposed is limited in several ways, and that life history theory provides a more explanatory and inclusive framework, making more specific predictions about the trade-offs faced by organisms in the allocation of bioenergetic and material resources.

We agree that sexual selection is a more comprehensive explanation for sex differences in direct aggression than social role theory, which is an unparsimonious and vestigial remnant of human exceptionalism. Nevertheless, Archer misses several opportunities to put the theoretical predictions made by himself and by others into direct competition in a way that would further the interests of strong inference.

Genes controlling the choice of sexual strategy must be sensitive to critical environmental contingencies, including the presence of other strategically relevant genetic traits. To determine which strategy works best for each individual, one must assess both its environment and itself within that environment. Psychosexual development involves an assessment of sociosexual affordances, strategically calibrating optimal utilization of physical and psychosocial assets.

Mealey distinguishes two types of sociopathy: (1) or obligate, and (2) or facultative. Either sociopathy evolved twice, or one form is derived from the other, e.g., through: (1) genetic assimilation generating polymorphism in the relative strength of biases favoring the development of otherwise facultative strategies, or (2) independently heritable but strategically relevant characteristics biasing the optimal selection of facultative strategies.

Burkart et al. present a paradox – general factors of intelligence exist among individual differences (g) in performance in several species, and also at the aggregate level (G); however, there is ambiguous evidence for the existence of g when analyzing data using a mixed approach, that is, when comparing individuals of different species using the same cognitive ability battery. Here, we present an empirical solution to this paradox.

The Continuous Parameter Estimation Model is applied to develop individual genomic-level heritabilities for the latent hierarchical structure and developmental dynamics of Life History (LH) strategy LH strategies relate to the allocations of bioenergetic resources into different domains of fitness. LH has moderate to high population-level heritability in humans, both at the level of the high-order Super-K Factor and the lower-order factors, the K-Factor, Covitality Factor, and General Factor of Personality (GFP). Several important questions remain unexplored. We developed measures of genome-level (...) heritabilities employing an American sample of 316 monozygotic (MZ) and 274 dizygotic (DZ) twin dyads and a Swedish sample of 863 MZ and 475 DZ twin dyads. This novel heritability index measures individual genetic transmissibility, therefore opening new avenues for analyzing complex interactions among heritable traits inaccessible to standard structural equations methods. For these samples: (1) moderate to high heritability of factor loadings of Super-K on its lower-order factors is demonstrated, evidencing biological preparedness, genetic accommodation, and the gene-culture coevolution of biased epigenetic rules of development; (2) moderate to high heritability of the magnitudes of the effect of the higher-order factors upon their loadings on their constituent factors, evidencing genetic constraints upon phenotypic plasticity; and (3) that heritability of the LH factors, of factor loadings, and of the magnitudes of the correlations among factors are weaker among those with slower LH speeds, demonstrating that inter-individual variation in transmissibility is a function of individual socioecological selection pressures. (shrink)

Baumard proposes that life history slowing in populations over time is the principal driver of innovation rates. We show that this is only true of micro-innovation rates, which reflect cognitive and economic specialization as an adaptation to high population density, and not macro-innovation rates, which relate more to a population's level of general intelligence.