The authors combine evolutionary theory with the anthropological study of kinship to account for cross-cultural diversity in birth-related investments by kin. Four hypotheses are formulated using paternal certainty, gender, and kinship laterality as independent variables. They test these hypotheses with data from the 60-culture Probability Sample of the Human Relations Area Files (HRAF). Their hypotheses are generally confirmed. For example, grandmothers and aunts provide more direct birth care than grandfathers and uncles. However, they did have some unanticipated results. Fathers provide as much direct birth care as grandmothers and aunts. In addition, they found paternal certainty to be a better predictor of direct birth care than kinship laterality, and kinship laterality to be a better predictor of indirect care. They explain this difference by arguing that direct birth care is the most important kind of investment kin make to ensure the survival and reproduction of mothers and newborns.

This study assessed the impact of utilization of an artificially intelligent geometry proof tutor on classroom social processes. Both teachers' and students' behaviors changed. Teachers devoted more time to their slower students, treated students in a more collegial fashion, and increased their emphasis on effort in grading students. Students showed a marked increase in task-related effort and involvement. This change appeared to be due to an increase both in the students' enjoyment of the class and in the level of peer competition.

In the indigenous Mexican village of Hueyapan, there is a clear contrast between the supernatural beliefs curers use to explain illness and the naturalistic assumptions made by this community's bonesetters. In addition to employing different conceptual models, the two types of healers differ with respect to their manner of recruitment, training, types of illnesses treated, social status, and gender. These differences add up to a seeming enigma: in a community where men largely control political, economic, and religious affairs, the higher status role of curer is undertaken most frequently by women and the lower status specialty of bonesetter by men. Hueyapan's health care system becomes less problematical, however, when it is recognized that recruitment to the bonesetter and curer roles is shaped by pragmatic considerations of role continuity and compatibility independent of the social status of these two occupations.

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This special issue "Evolutionary Approaches to Cross-Cultural Anthropology" brings together scholars from the fields of behavioral ecology, evolutionary psychology, and cultural evolution whose cross-cultural work draws on evolutionary theory and methods. The papers here are a subset of those presented at a symposium we organized for the 2011 meeting of the Society for Cross-Cultural Research held in Charleston, South Carolina. Collectively, our authors show how an engagement with cultural variation has enriched evolutionary anthropology, and these papers showcase how cross-cultural research can benefit from the theoretical and methodological contributions of an evolutionary approach.