This study tests the weaning food availability hypothesis, that both the introduction of foods other than breastmilk and the cessation of breastfeeding will vary by society's subsistence type. This hypothesis has implications for demography, as accelerated weaning can lead to increases in both mothers' fertility (due to decreased birth intervals) and infant mortality (due to the presence of pathogens in new foods).

This study tests the weaning food availability hypothesis, that both the introduction of foods other than breastmilk and the cessation of breastfeeding will vary by society's subsistence type. This hypothesis has implications for demography, as accelerated weaning can lead to increases in both mothers' fertility (due to decreased birth intervals) and infant mortality (due to the presence of pathogens in new foods).

This article reassesses the question of relative peacefulness/violence of preindustrial societies. It tests two materialist theories suggesting that more advanced subsistence techniques and population pressure will increase the likelihood of warfare.

This study examines the relationship between drug foods and colonialism in relation to labor and trade. Relationships were found between political complexity, subsistence type, and the use of drug foods as labor and trade enhancers and inducers.

This article investigates peer relations in infancy, both in primates and in preindustrial human societies. Data from these populations shows a strong tendency toward a multi-age composition of play groups rather than solely peer-aged play groups for infants. Patterns in child care across societies of different subsistence types are empirically examined.

This study examines the relationship between personality traits and subsistence type in mixed farming and pastoralists societies. Findings suggest that differences in child socialization do not significantly predict personality differences in mixed farming and pastoralist societies as much as one would expect. Adult experiences should be considered as better predictors of personality traits.

This study uses logistic regression to test the relationship between homosexuality and ecological and psychosocial variables. Significant associations were found between the frequency of homosexuality and type of agriculture, the occurrence of gathering, and psychosocial stressors in women's lives.

The association between hunting and sign language is examined. It is hypothesized that sign language develops as a form of nonverbal communication to aid hunters in the coordinated stalking of game. Ethnographic evidence supports this hypothesis. A second hypothesis is also tested concerning the relationship between population size and non-verbal communication, however sampling procedures provided an inadequate test of this hypothesis.

This article investigates peer relations in infancy, both in primates and in preindustrial human societies. Data from these populations shows a strong tendency toward a multi-age composition of play groups rather than solely peer-aged play groups for infants. Patterns in child care across societies of different subsistence types are empirically examined.

This study tests possible explanations for sexual dimorphism in human post-reproductive life-spans. The author focuses on explanations involving male paternal investment and finds that men in agricultural societies are more likely to invest in their offspring than men in hunter-gatherer societies.