Human Life History Strategies Research Articles

Multiproxy bioarchaeological data reveals interplay between growth, diet and population dynamics across the transition to farming in the central Mediterranean

The transition to farming brought on a series of important changes in human society, lifestyle, diet and health. The human bioarchaeology of the agricultural transition has received much attention, however, relatively few studies have directly tested the interrelationship between individual lifestyle factors and their implications for understanding life history changes among the first farmers. We investigate the interplay between skeletal growth, diet, physical activity and population size across 30,000 years in the central Mediterranean through a ‘big data’ cross-analysis of osteological data related to stature (n = 361), body mass (n = 334) and long bone biomechanics (n = 481), carbon (δ13C) and nitrogen (δ15N) stable isotopes (n = 1986 human, n = 475 animal) and radiocarbon dates (n = 5263). We present the observed trends on a continuous timescale in order to avoid grouping our data into assigned ‘time periods’, thus achieving greater resolution and chronological control over our analysis. The results identify important changes in human life history strategies associated with the first farmers, but also highlight the long-term nature of these trends in the millennia either side of the agricultural transition. The integration of these different data is an important step towards disentangling the complex relationship between demography, diet and health, and reconstruct life history changes within a southern European context. We believe the methodological approach adopted here has broader global implications for bioarchaeological studies of human adaptation more generally.

Childhood environmental harshness and unpredictability negatively predict eHealth literacy through fast life-history strategy.

eHealth literacy-the ability to obtain, understand, evaluate, and use health information from the Internet-is important to maintaining and improving personal health. Prior research found that people differ notably in the levels of eHealth literacy, and this study tests a theoretical account of some of those individual differences. Drawing on life history theory, we propose that low eHealth literacy is partly the outcome of people adopting a resource-allocation strategy emphasizing early and fast reproduction, namely, a fast life-history strategy. We conducted a cross-sectional survey study (N = 1,036) that measured Chinese adult respondents' eHealth literacy, childhood environmental harshness and unpredictability, and fast life-history strategy. Covariates included health-information seeking online, self-rated health, sex, age, education level, and monthly income. Supporting a life-history explanation of eHealth literacy, childhood environmental harshness and unpredictability negatively predicted eHealth literacy through fast life-history strategy and mainly the insight-planning-control dimension of it. Harshness, not unpredictability, also directly and negatively predicted eHealth literacy after fast life-history strategy was controlled for. Our findings suggest that the psychological mechanisms associated with human life-history strategies produce at least some of the individual differences in levels of eHealth literacy, including those related to neuroticism, socioeconomic status, self-rated health and social capital. Thus, a possible way to increase future generation's eHealth literacy and thereby their health is to reduce the harshness and unpredictability of the environment in which they grow up, thereby making them more likely to adopt a relatively slow life-history in their adulthood.

Postpartum amenorrhea duration by sex of the newborn in two natural fertility populations.

Postpartum amenorrhea (PA) affects the length of interbirth intervals and thus is intimately related to human life history strategies. PA duration appears to be influenced by maternal energetic status. In humans, as in other mammals, sons are costlier than daughters. Thus, we hypothesize that, in energetically constrained environments, a newborn's sex should be associated with PA duration. We analyzed data from two natural fertility populations in which mothers have differing energy budgets: Qom women (n = 121) from a periurban village in Argentina, who have a comparatively calorically dense diet and are sedentary (prepregnancy mean BMI = 24.8 ± 4.5 kg/m2 in 1997), and agropastoral Kaqchikel Maya women (n = 88), who have a comparatively calorically restricted diet and high physical activity levels (mean BMI = 21.8 ± 3.7 kg/m2 ). We predict that (a) mothers of sons exhibit longer PA duration than mothers of daughters and (b) this association between offspring sex and PA duration is stronger in the Maya, who have smaller energy budgets. Maya mothers with sons exhibited estimated mean and median PA durations that were 1.34 times the estimated mean and median PA duration of mothers with daughters (p = 0.02). Among the Qom, mean, and median PA duration did not differ significantly in relation to offspring sex (p = 0.94). Maya mothers with sons exhibited longer PA duration than those with daughters. This phenomenon was not observed in the well-nourished Qom, possibly due to "buffering" effects from larger energy budgets. Offspring sex may influence birth spacing and maternal life history strategies in energetically constrained environments.

Sex-Specific Associations of Harsh Childhood Environment with Psychometrically Assessed Life History Profile: no Evidence for Mediation through Developmental Timing or Embodied Capital

Life History (LH) Theory explains how organisms allocate energy among the competing demands of growth and maintenance (i.e., investment in future reproduction), mating effort, and parenting effort. LH profile is thought to be influenced by cues of extrinsic mortality and morbidity. Human LH strategies have been conceptualized on a fast-slow continuum and have been measured via biometric indicators (e.g., developmental timing) and psychometric indictors (e.g., personality traits). We aim to preliminarily develop and test an integrated model in which childhood environments are hypothesized to influence variation in psychometric LH profile in adulthood via effects on earlier biometric developmental LH indicators. We tested, in a sample of 370 U.S. undergraduates, a model in which associations of early life adversity on psychometrically assessed LH profile are mediated by biometrically assessed LH indicators (e.g., developmental timing; somatic state). The complete model was not supported. Several direct and indirect paths were consistent with theory-driven predictions, but other findings were inconsistent with LH-based hypotheses. Best fitting models differed by sex, such that an association existed between males’ psychometric LH profile and neighborhood stress, father closeness, and somatic state (telomere length), whereas an association existed between females’ developmental timing with adult LH profile and father closeness. While there was limited support for the complete multivariate model, we conclude that an integrative approach to the assessment and modeling of LH variation holds substantial promise for future research.

Life History Transitions at the Origins of Agriculture: A Model for Understanding How Niche Construction Impacts Human Growth, Demography and Health.

Over recent millennia, human populations have regularly reconstructed their subsistence niches, changing both how they obtain food and the conditions in which they live. For example, over the last 12,000 years the vast majority of human populations shifted from foraging to practicing different forms of agriculture. The shift to farming is widely understood to have impacted several aspects of human demography and biology, including mortality risk, population growth, adult body size, and physical markers of health. However, these trends have not been integrated within an over-arching conceptual framework, and there is poor understanding of why populations tended to increase in population size during periods when markers of health deteriorated. Here, we offer a novel conceptual approach based on evolutionary life history theory. This theory assumes that energy availability is finite and must be allocated in competition between the functions of maintenance, growth, reproduction, and defence. In any given environment, and at any given stage during the life-course, natural selection favours energy allocation strategies that maximise fitness. We argue that the origins of agriculture involved profound transformations in human life history strategies, impacting both the availability of energy and the way that it was allocated between life history functions in the body. Although overall energy supply increased, the diet composition changed, while sedentary populations were challenged by new infectious burdens. We propose that this composite new ecological niche favoured increased energy allocation to defence (immune function) and reproduction, thus reducing the allocation to growth and maintenance. We review evidence in support of this hypothesis and highlight how further work could address both heterogeneity and specific aspects of the origins of agriculture in more detail. Our approach can be applied to many other transformations of the human subsistence niche, and can shed new light on the way that health, height, life expectancy, and fertility patterns are changing in association with globalization and nutrition transition.

Environmental stress and human life history strategy development in rural and peri-urban South India

Abstract Few studies have examined the role of early vs. later environment in the development of life history (LH) strategies, whether age at sexual debut mediates LH development, or whether LH indicators contribute to environmental stress in adulthood. In the current study, we addressed these gaps cross-culturally using data from Jenu Kurubas who live in the rural outskirts of Mysore (n = 133), India, and mixed-caste peri-urban residents in Mysore city (n = 222). Research took place from October 2016–July 2017. First, participants engaged in semi-structured interviews to formulate quantitative measures of current environmental stress (n = 60). Next, participants (n = 355) completed structured questionnaires that measured demographics; early and current environmental stress; and LH indicators including age at sexual debut, facets of impulsivity, education, and number of children. Structural equation modeling was used to test for the developmental cascade reported in Western studies of psychosocial acceleration (e.g., indirect effect of early environmental stress on number of children through age at sexual debut). Consistent with Western findings, environmental stress appeared to hasten sexual debut, decrease self-regulation and educational attainment, and increase current environmental stress in the peri-urban sample. Early environmental stress forecasted younger age at sexual debut in both samples; however, no other effects of early environmental stress nor any associations with current environmental stress were consistent between samples. Although age at sexual debut appeared to translate early environmental stress into greater numbers of children and current environmental stress in the peri-urban and rural samples, respectively, it was associated with different outcomes between the samples and forecasted adult environment only in the rural sample. Taken together, our findings indicate more research is needed to determine whether the developmental cascade suggested by most applications of LH theory to humans generalizes across cultures and rural and peri-urban environments.

Studying Sex Differences in Psychosocial Life History Indicators

The last decade has seen rapid growth in the study of human life history strategies, with advances to theory, increasingly sophisticated research designs, and innovative new tools now being at the disposal of researchers. Contemporary evolutionary psychology suggests there should be variation in biological and psychological traits attributable to differences between the sexes. We review theory underpinning sex differences in evolutionarily adaptive behaviors and then outline the developmental stages and behaviors pertinent to life history strategies that could be subject to these differences. We then review contemporary work that has examined sex in relation to these domains and end with recommendations for future research agendas. We conclude that future work needs to consider sex more comprehensively (studying the sexes separately when necessary) when evaluating measures and models designed to tackle important life history research questions.

War and Peace: A Diachronic Social Biogeography of Life History Strategy and Between-Group Relations in Two Western European Populations

We report successful diachronic replication of two major sets of prior findings in the social biogeography of human life history (LH) strategy: (1) the constructive replication of the diachronic changes in the latent hierarchical structure of intelligence in Britannic populations, but as presently applied to the latent hierarchical structure of human LH strategy, now cross-validated in both Britannic and Gallic populations; and (2) the diachronic replication in both Britannic and Gallic populations of the structural relations found synchronically among human LH strategy, between-group competition, and economic productivity in cross-sectional data on contemporary samples of both national and subnational polities. In addition, a supplementary methodological objective was: (3) the convergent validation of diachronic lexicographic measures of LH strategy with respect to more traditional non-lexicographic indicators of LH strategy, such as infant mortality rates, total fertility rates, and life expectancies. We obtained complete configural invariance across Britannic and Gallic biocultural groups, meaning that the same model predictors were statistically significant, but incomplete metric invariance, meaning that most but not all model parameter estimates were statistically equivalent in magnitude and direction. All new results obtained from diachronic data in Britannic populations were replicated almost perfectly in Gallic populations.

Life history correlates of human (Homo sapiens) ejaculate quality.

Life history strategies reflect resource allocation decisions, which manifest as physiological, psychological, and behavioral traits. We investigated whether human ejaculate quality is associated with indicators of relatively fast (greater resource allocation to mating effort) or slow (greater resource allocation to parenting effort) life history strategies in a test of two competing hypotheses: (a) The phenotype-linked fertility hypothesis, which predicts that men pursuing a relatively fast life history strategy will produce higher quality ejaculates, and (b) the cuckoldry-risk hypothesis, which predicts that men pursuing a relatively slow life history strategy will produce higher quality ejaculates. Men (n = 41) completed a self-report measure assessing life history strategy and provided two masturbatory ejaculate samples. Results provide preliminary support for the cuckoldry-risk hypothesis: Men pursuing a relatively slow life history strategy produced higher quality ejaculates. Ejaculate quality may therefore reflect resource allocation decisions for greater parenting effort, as opposed to greater mating effort. The findings contribute informative data on correlations between physiological and phenotypic indicators of human life history strategies. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The Future of Human Longevity: Time for a Reality Check

Gavrilov and colleagues disagree with our article in Gerontology [Vijg and Le Bourg: Gerontology 2017;63:432-434]. Here we address their arguments regarding human life-history strategies, maximal lifespan, and the proposal that one could live soon for 150 years.

On the Psychometric Study of Human Life History Strategies.

This article attends to recent discussions of validity in psychometric research on human life history strategy (LHS), provides a constructive critique of the extant literature, and describes strategies for improving construct validity. To place the psychometric study of human LHS on more solid ground, our review indicates that researchers should (a) use approaches to psychometric modeling that are consistent with their philosophies of measurement, (b) confirm the dimensionality of life history indicators, and (c) establish measurement invariance for at least a subset of indicators. Because we see confirming the dimensionality of life history indicators as the next step toward placing the psychometrics of human LHS on more solid ground, we use nationally representative data and structural equation modeling to test the structure of middle adult life history indicators. We found statistically independent mating competition and Super-K dimensions and the effects of parental harshness and childhood unpredictability on Super-K were consistent with past research. However, childhood socioeconomic status had a moderate positive effect on mating competition and no effect on Super-K, while unpredictability did not predict mating competition. We conclude that human LHS is more complex than previously suggested-there does not seem to be a single dimension of human LHS among Western adults and the effects of environmental components seem to vary between mating competition and Super-K.

From Environment to Mating Competition and Super-K in a Predominantly Urban Sample of Young Adults.

Recent research suggests human life history strategy (LHS) may be subsumed by multiple dimensions, including mating competition and Super-K, rather than one. In this study, we test whether a two-dimensional structure best fit data from a predominantly urban sample of young adults ages 18–24. We also test whether latent life history dimensions are associated with environmental harshness and unpredictability as predicted by life history theory. Results provide evidence that a two-dimensional model best fit the data. Furthermore, a moderate inverse residual correlation between mating competition and Super-K was found, consistent with a life history trade-off. Our findings suggest that parental socioeconomic status may enhance investment in mating competition, that harshness might persist into young adulthood as an important correlate of LHS, and that unpredictability may not have significant effects in young adulthood. These findings further support the contention that human LHS is multidimensional and environmental effects on LHS are more complex than previously suggested. The model presented provides a parsimonious explanation of an array of human behaviors and traits and can be used to inform public health initiatives, particularly with respect to the potential impact of environmental interventions.

Human Life History Strategies.

Human life history (LH) strategies are theoretically regulated by developmental exposure to environmental cues that ancestrally predicted LH-relevant world states (e.g., risk of morbidity-mortality). Recent modeling work has raised the question of whether the association of childhood family factors with adult LH variation arises via (i) direct sampling of external environmental cues during development and/or (ii) calibration of LH strategies to internal somatic condition (i.e., health), which itself reflects exposure to variably favorable environments. The present research tested between these possibilities through three online surveys involving a total of over 26,000 participants. Participants completed questionnaires assessing components of self-reported environmental harshness (i.e., socioeconomic status, family neglect, and neighborhood crime), health status, and various LH-related psychological and behavioral phenotypes (e.g., mating strategies, paranoia, and anxiety), modeled as a unidimensional latent variable. Structural equation models suggested that exposure to harsh ecologies had direct effects on latent LH strategy as well as indirect effects on latent LH strategy mediated via health status. These findings suggest that human LH strategies may be calibrated to both external and internal cues and that such calibrational effects manifest in a wide range of psychological and behavioral phenotypes.

Measures of domain-specific resource allocations in life history strategy: Indicators of a latent common factor or ordered developmental sequence?

The psychometric trait approach to human life history, based on common factor modeling, has recently come under some criticism for neglecting to inquire into the developmental progression that orients and executes human life history trajectories (Copping, Campbell, & Muncer, 2014). It was asserted that the psychometric approach wholly focuses on creating a higher-order latent factor of life history by subsuming individual differences with developmental and social experiences, ignoring ontogenetic progression. Implicit in the critique is the assumption that developmental perspectives and latent approaches are mutually exclusive and incompatible with each other. The response to this critique by Figueredo and colleagues (2015) proposed instead that developmental perspectives and latent trait approaches are both compatible and necessary to further research on human life history strategies. The current paper uses three independent cross-sectional samples to examine whether models of human life history are best informed by a developmental perspective, psychometric trait approach, or both.

Measures of domain-specific resource allocations in life history strategy: Indicators of a latent common factor or ordered developmental sequence?

The psychometric trait approach to human life history, based on common factor modeling, has recently come under some criticism for neglecting to inquire into the developmental progression that orients and executes human life history trajectories (Copping, Campbell, & Muncer, 2014). It was asserted that the psychometric approach wholly focuses on creating a higher-order latent factor of life history by subsuming individual differences with developmental and social experiences, ignoring ontogenetic progression. Implicit in the critique is the assumption that developmental perspectives and latent approaches are mutually exclusive and incompatible with each other. The response to this critique by Figueredo and colleagues (2015) proposed instead that developmental perspectives and latent trait approaches are both compatible and necessary to further research on human life history strategies. The current paper uses three independent cross-sectional samples to examine whether models of human life history are best informed by a developmental perspective, psychometric trait approach, or both.

Development of Japanese version of the long-term mating orientation scale (LTMO-J)

The purpose of this study was to validate the 7-item long-term mating orientation scale (LTMO) as translated into Japanese. Two samples of Japanese adults (N = 2000; 50.0% male; Mage = 40.9 for the first survey; N = 300; 54.7% male; Mage = 42.4 for the second survey) completed a web-based questionnaire, including the Japanese translation of the LTMO. The results showed that the psychometric properties of the Japanese LTMO scale were comparable to those of the original English version. The scale had adequate reliability based on Cronbach's α and McDonald's ω. Convergent validity was demonstrated by the correlation between the LTMO scores and related variables: human life history strategies, short-term sociosexual orientation, attitude to infidelity, romantic attachment style, and so on. The translated scale provides a valid and reliable instrument in Japanese that measures human mating strategy.

Methodologically Sound: Evaluating the Psychometric Approach to the Assessment of Human Life History [Reply to

Copping, Campbell, and Muncer (2014) have recently published an article critical of the psychometric approach to the assessment of life history (LH) strategy. Their purported goal was testing for the convergent validation and examining the psychometric structure of the High-K Strategy Scale (HKSS). As much of the literature on the psychometrics of human LH during the past decade or so has emanated from our research laboratory and those of close collaborators, we have prepared this detailed response. Our response is organized into four main sections: (1) A review of psychometric methods for the assessment of human LH strategy, expounding upon the essence of our approach; (2) our theoretical/conceptual concerns regarding the critique, addressing the broader issues raised by the critique regarding the latent and hierarchical structure of LH strategy; (3) our statistical/methodological concerns regarding the critique, examining the validity and persuasiveness of the empirical case made specifically against the HKSS; and (4) our recommendations for future research that we think might be helpful in closing the gap between the psychometric and biometric approaches to measurement in this area. Clearly stating our theoretical positions, describing our existing body of work, and acknowledging their limitations should assist future researchers in planning and implementing more informed and prudent empirical research that will synthesize the psychometric approach to the assessment of LH strategy with complementary methods.

Human Life History Dimensions in Reproductive Strategies Are Intuitive Across Cultures

Psychological research has been criticized for its extensive use of American university students to make broad claims about human psychology and behavior. Critics recommend a broader base of participants because there is substantial variability in experimental results across populations, and North American and Western European psychology pool participants may be outliers in comparison with the rest of the species. This challenge is especially pertinent for claims of species-universal evolved psychological architecture. One such claim has been made regarding recognition of human life history strategies. For example, previous research demonstrates that North American women and men can identify male and female characters with fast (high mating effort, low parental investment) and slow (low mating effort, high parental investment) life history strategies, make accurate predictions about their behavioral tendencies, and respond to them in ways that would facilitate participants’ own reproductive success. The current project validates the understanding of fundamental life history dimensions across a wide range of cultures, therefore supporting the idea that there is a universality in human’s ability to use, and perceive others’ use of, life history strategies. Results for each language sample replicated patterns from North American participants. Ratings for characters clustered into two dimensions, mating effort and parental investment. Items most central to the theoretical constructs had the highest factor loadings.

The psychometric assessment of human life history strategy: A meta-analytic construct validation.

A growing body of empirical literature supports the validity of psychometric assessments of human life history strategies, but no comprehensive quantitative summaries have yet been published. We present a psychometric validation study of a 20-item Short-Form of the Arizona Life History Battery (ALHB), the Mini-K, using metaanalytic procedures to survey a multiplicity of published and unpublished studies on English-speaking North American college student samples. Correlations between the Mini-K with other measures of related constructs describe the dimensions of the

Plasticity in Human Life History Strategy

The life history of Homo sapiens is characterized by a lengthy period of juvenile dependence that requires extensive allocare, short interbirth intervals with concomitantly high fertility rates, and a life span much longer than that of other extant great apes. Although recognized as species-defining, the traits that make up human life history are also notable for their extensive within- and between-population variation, which appears to trace largely to phenotypic and developmental plasticity. In this review, we first discuss the adaptive origins of plasticity in life history strategy and its influence on traits such as growth rate, maturational tempo, reproductive scheduling, and life span in modern human populations. Second, we consider the likely contributions of this plasticity to evolutionary diversification and speciation within genus Homo. Contrary to traditional assumptions that plasticity slows the pace of genetic adaptation, current empirical work and theory point to the potential for plasticity...