Mark V. Flinn

Mate guarding in a Caribbean village

Behavioral observation, economic, and genealogical data collected in a rural Trinidadian village indicate: (1) males courting the same females have higher rates of agonistic interactions (e.g., arguing, fighting) with each other than they do with other males; (2) females courting the same males do not have higher rates of agonistic interactions with each other than they do with other females; (3) exclusive (monogamous) mating relationships have lower rates of agonistic interactions than nonexclusive (polygamous) mating relationships; (4) coresident mates interact more frequently when the female is fecund; (5) coresident mates have higher rates of agonistic interactions when the female is fecund; (6) males with fecund mates have higher rates of agonistic interactions with other unrelated males than do males with infecund mates; (7) fecund females do not have higher rates of agonistic interactions with other females than do infecund females; and (8) females do not guard prosperous males (those from households with 6 or more acres of land) more intensely than poorer males. These results suggest that mate guarding is an important aspect of reproductive competition, and that there are significant male/female differences in mate guarding strategies in this human population.

Evolution of Human Parental Behavior and the Human Family

Objective. To develop an evolutionary model that integrates human parenting and family formation with ideas about the evolved functions of distinctive human characteristics, such as concealed ovulation and sophisticated sociocognitive competencies. Design. Theoretical and empirical research across scientific disciplines is reviewed. The emphasis is on ecological and social conditions that covary, across species, with parenting, family formation, and potentially coevolving characteristics, such as a long developmental period. Results. For humans, social competition through coalition formation emerges as the key selective pressure that readily explains the coevolution of a constellation of characteristics that covary with parenting and family formation, including a lengthy developmental period, reduced sexual dimorphism, concealed ovulation, menopause, complex kinship networks, large brains, and sophisticated sociocognitive competencies. Individual and cross-cultural variations in patterns of parenting dynamics and family formation are viewed as adaptive phenotypic responses to different ecological and historical conditions. Conclusions. Human parenting and family formation are features of a coevolving suite of distinctive human characteristics, the evolutionary function of which is to facilitate the formation of kin-based coalitions for competition with other coalitions for resource control. In this view, a central function of human parenting and the human family is to provide a context for the development of sociocompetitive competencies appropriate to the local ecology.

Social economics of childhood glucocorticoid stress response and health

This study examines socioeconomic conditions, psychosocial stress, and health among 264 infants, children, adolescents, and young adults aged 2 months to 18 years residing in a rural Caribbean village. Fieldwork was conducted over a 9 year period (1988-1996). Research methods and techniques include salivary cortisol radioimmunoassay (N = 22,438), systematic behavioral observations, psychological questionnaires, health evaluations, medical records, informal interviews, and participant observation. Analyses of data indicate complex relations among socioeconomic conditions, stress, and health. Household income, land ownership, parental education, and other socioeconomic measures are weakly associated with child illness. There is no evidence that apparent material benefits of high socioeconomic status--such as improved housing, diet, work loads, and access to private healthcare--have important direct effects on child health in this population. However, social relationships, especially family environment, may have important effects on childhood psychosocial stress and illness. Abnormal glucocorticoid response profiles, diminished immunity, and frequent illness are associated with unstable mating relationships for parents/caretakers and household composition. We suggest that family relationships and concomitant stress and immunosuppression are important intermediary links between socioeconomic conditions and child health.

Correlates of Reproductive Success In a Caribbean Village

Genealogical, demographic, and economic data collected in a rural Trinidadian village indicate that: (1) individuals with more land have more offspring, (2) males with more land have higher mating success, (3) young adults with parents resident in the village have higher reproductive success, and (4) the residence of father has a strong effect on young adult male reproductive success, but apparently has no effect on young adult female reproductive success, suggesting a gender bias in nepotism. The results indicate that there are important gender differences in the effect of resources on reproduction and in patterns of parent-offspring interaction.

Culture Theory: The Developing Synthesis from Biology

ConclusionsWe believe that a useful, complete theory of culture is simpler than the dichotomies promoted by the coevolutionary approach suggest. Culture can be regarded as an aspect of the environment into which each human is born and must succeed or fail, developed gradually by the succession of humans who have lived throughout history. We hypothesize that culture results from the inclusive-fitness-maximizing efforts of all humans who have lived. We think the evidence suggests that cultural traits are, in general, vehicles of genic survival, and that the heritability of cultural traits depends on the judgments (conscious and unconscious) of individuals with regard to their effects on the individuals inclusive fitness.The challenge now before students of culture is to understand the proximate mechanisms, especially the ontogeny of learning biases, that result in the acquisition and transmission of cultural traits. How, for example, do we learn what constitutes an appropriate return on a social investment in different circumstances; i.e., what causes us to feel rewarded by, say, helping offspring who do not help us back, yet consistently to begrudge lesser expenditures to most others, or to feel cheated if we are not compensated for such expenditures immediately? We suggest that the answers to such questions lie in a few basic evolved learning tendencies.

Step- and genetic parent/offspring relationships in a Caribbean village

Abstract Ethnographic data from a rural Trinidadian village were examined to test for differences in step-and genetic parent/offspring relationships. The data indicated that when both step- and genetic offspring are co-resident in the same household, fathers interact more frequently and less agonistically with genetic offspring than they do with step-offspring. Contrary to predictions from attachment theory, two possible mechanisms for paternal attachment, duration of co-residence and co-residence at birth, are associated with lower rates of interaction, and higher rates of agonistic interaction with stepoffspring. The data also indicate gender differences in step- and genetic parent/ offspring relationships, higher rates of “fosterage” for stepoffspring, higher rates of emigration from the village for stepoffspring, and lower reproductive success for individuals raised by a stepparent.

Male-female differences in effects of parental absence on glucocorticoid stress response.

This study examines the family environments and hormone profiles of 316 individuals aged 2 months-58 years residing in a rural village on the east coast of Dominica, a former British colony in the West Indies. Fieldwork was conducted over an eight-year period (1988–1995). Research methods and techniques include radioimmunoassay of cortisol and testosterone from saliva samples (N=22,340), residence histories, behavioral observations of family interactions, extensive ethnographic interview and participant observation, psychological questionnaires, and medical examinations.Analyses of data indicate complex, sex-specific effects of family environment on endocrine function. Male endocrine profiles exhibit greater sensitivity to presence of father than do female endocrine profiles. Father-absent males tend to have (a) low cortisol levels during infancy, (b) high or abnormal cortisol profiles during childhood and adolescence, and (c) high cortisol and low testosterone levels during adulthood compared with those of males raised with a resident father. These results indicate that early family environment has significant effects on endocrine response throughout male life histories.

Explaining Biased Sex Ratios in Human Populations: A Critique of Recent Studies [and Comments and Reply]

DANIELA F. SIEFF is a graduate student in human ecology at the University of California, Davis (Davis, Calif. 956I6, U.S.A.). Born in I965, she received a B.A. from Oxford University in I987 and an M.A. in anthropology and psychology from the University of Michigan in I989. Her research interests are parental-investment strategies and the costs of children in traditional societies. She is currently engaged in a study of the interaction of womens work, polygyny, fertility, and child care among the Dotoga pastoralists of northern Tanzania. The present paper was submitted in final form 30 vi 89.

Evolutionary History of Hunter-Gatherer Marriage Practices

Background The universality of marriage in human societies around the world suggests a deep evolutionary history of institutionalized pair-bonding that stems back at least to early modern humans. However, marriage practices vary considerably from culture to culture, ranging from strict prescriptions and arranged marriages in some societies to mostly unregulated courtship in others, presence to absence of brideservice and brideprice, and polyandrous to polygynous unions. The ancestral state of early human marriage is not well known given the lack of conclusive archaeological evidence. Methodology Comparative phylogenetic analyses using data from contemporary hunter-gatherers around the world may allow for the reconstruction of ancestral human cultural traits. We attempt to reconstruct ancestral marriage practices using hunter-gatherer phylogenies based on mitochondrial DNA sequences. Results Arranged marriages are inferred to go back at least to first modern human migrations out of Africa. Reconstructions are equivocal on whether or not earlier human marriages were arranged because several African hunter-gatherers have courtship marriages. Phylogenetic reconstructions suggest that marriages in early ancestral human societies probably had low levels of polygyny (low reproductive skew) and reciprocal exchanges between the families of marital partners (i.e., brideservice or brideprice). Discussion Phylogenetic results suggest a deep history of regulated exchange of mates and resources among lineages that enhanced the complexity of human meta-group social structure with coalitions and alliances spanning across multiple residential communities.

Evolutionary functions of early social modulation of hypothalamic-pituitary-adrenal axis development in humans.

The hypothalamic-pituitary-adrenal axis (HPAA) is highly responsive to social challenges. Because stress hormones can have negative developmental and health consequences, this presents an evolutionary paradox: Why would natural selection have favored mechanisms that elevate stress hormone levels in response to psychosocial stimuli? Here we review the hypothesis that large brains, an extended childhood and intensive family care in humans are adaptations resulting from selective forces exerted by the increasingly complex and dynamic social and cultural environment that co-evolved with these traits. Variations in the modulation of stress responses mediated by specific HPAA characteristics (e.g., baseline cortisol levels, and changes in cortisol levels in response to challenges) are viewed as phenotypically plastic, ontogenetic responses to specific environmental signals. From this perspective, we discuss relations between physiological stress responses and life history trajectories, particularly the development of social competencies. We present brief summaries of data on hormones, indicators of morbidity and social environments from our long-term, naturalistic studies in both Guatemala and Dominica. Results indicate that difficult family environments and traumatic social events are associated with temporal elevations of cortisol, suppressed reproductive functioning and elevated morbidity. The long-term effects of traumatic early experiences on cortisol profiles are complex and indicate domain-specific effects, with normal recovery from physical stressors, but some heightened response to negative-affect social challenges. We consider these results to be consistent with the hypothesis that developmental programming of the HPAA and other neuroendocrine systems associated with stress responses may facilitate cognitive targeting of salient social challenges in specific environments.