In this article the researcher conducted five different studies on in-group or "we-group" vs out-group or "they-group" discrimination practices. Two previous hypotheses are re-examined, the pathogen stress hypothesis and the rice-wheat hypothesis, in order to explain heightened ingroup-outgroup differentiation, before turning to overarching geographical hypothesis. Each of the five studies look at a different group of societies cross-culturally, ending in an index of intergroup discrimination by individuals across 222 countries in study 5. All five studies conclude that differentiation between us and them varies based on geographical location and more specifically, along latitude.

Genetic, linguistic, and geographic data can be used to explain the distribution of cultural units ("semes") and to understand the evolutionary mechanisms of culture. Three broad models of cultural transmission attempt to explain why cultures share semes: (1) Cultural diffusion, emphasizing horizontal transmission. (2) Local adaptation, where trail-and-error learning leads to the independent adoption of semes by different peoples living in similar environments. (3) Demic diffusion, which emphasizes vertical and frequency-dependent transmission. Authors test the explanatory power of each model using cultural, genetic, linguistic and geographic data from 36 African cultures.

This article examines predictors of intimacy between husbands and wives. Emphasis is on equality of spouses. A causal model is presented.

The author investigates the associations between production relations, the character of productive forces, and sexual life. A significant correlation was found between production relations and the character of productive forces. Results also showed that more sexual freedom is associated with higher level of development of productive forces and an absence of internal oppression.

This study examines relationships among descent, marriageable relatives, residence, family, and mode of production.

Based on work by Rosenblatt (1966), this article tests a hypothesis relating sexual freedom to romantic love. Findings suggest a relationship between premarital and extramarital sexual permissiveness equality for women and men and romantic love.

Previous cross-cultural studies of romantic love have, in the authors' view, been plagued by vague definitions of the concept and a conflation of cultural, bio-psychological, and social factors. Thus, the authors distinguish between the social aspect of romantic love (which they argue is a universal human predisposition) and the variable cultural valuation of romance. In a large cross-cultural sample, the authors test the hypotheses that gender equality and family organization are important predictors of the cultural valuation of romantic love.

This paper presents research on the factors that promote romantic love as a basis for marriage in non-industrial societies. After a discussion of the previous literature on romantic love in ethnographic societies, the authors used the SCCS, EA, and data from eHRAF to create a data set of 109 cultures and then utilized multiple ordinal regression to test the relationship between different types of families and post-marital residence practices and the importance of romantic love in marriage. The findings show that monogamy is significantly correlated with romantic love, while nuclear family organization and neolocal post-marital residence are not significantly correlated. The presence of polygyny is found to lower the probability of romantic love being a basis for marriage. These findings contradict previous research, which found a relationship between non-neolocal post-marital residence and the presence of romantic love in marriage.

Through review of the economic literature and cross-cultural analysis of families (nuclear, stem, and complex), the authors show that family type is heterogeneous and argue that types other than nuclear have been largely ignored by economists. They encourage, based on their findings, further research on family structure and the development of better models for household decision making. They use ancestral populations in the ethnographic record to estimate country-level family patterns.

This study focuses on preferences for thinness or fatness in women cross-culturally. Results contradict previous studies and the hypothesis that preference for fatness in women is predicted by resource scarcity. Alternative explanations for valuation of fatness are explored, including climate and male dominance.