Fitness Costs Predict Emotional, Moral, and Attitudinal Inbreeding Aversion

Attitudes Towards Cousin Marriages: Findings Among Young People from Mexico

The present research examined how life history and resistance against interethnic mating were related to positive and negative attitudes towards cousin marriages among young people aged between 15 and 25 from a rural area in the Mexican state of Oaxaca. The sample included three ethnic groups: Mestizos (people of mixed Spanish and indigenous descent, n = 84), indigenous Mixtecs (n = 83), and Afro-Mexicans (n = 33). In general, respondents reported more negative than positive attitudes towards cousin marriage. Among the Mestizos, but not in the other ethnic groups, women reported more negative attitudes than men did. The main objections against marrying a cousin were that it might lead to family conflict and might result in genetic defects of one’s offspring. The main positive aspect of cousin marriage that participants mentioned was that one would marry someone with the same values. The ethnic groups did not differ in their attitudes towards cousin marriages. A slower life history was related to a more negative (but not a less positive) attitude towards cousin marriages, whereas resistance against out-group mating was related to a more positive (but not a less negative) attitude towards cousin marriages. The implications of the results are discussed in the context of life history theory, the benefits of in-group marriage, and the potential positive and negative effects of cousin marriages.

An Examination of the Westermarck Hypothesis and the Role of Disgust in Incest Avoidance Among Fathers

From an evolutionary perspective, incestuous behavior is puzzling. The goal of this study was to assess the tenability of the Westermarck hypothesis (1891, 1921)-that people who live in close physical proximity with one another during childhood will develop a sexual indifference or aversion toward one another-and the mediating role of disgust as an incest avoidance mechanism in father-daughter relationships. A sample of fathers with daughters ( N = 632) from Canada and the United States were recruited by Qualtrics-a survey platform and project management company-to complete an online survey. The results from this study did not support the viability of the Westermarck hypothesis as a mechanism that facilitates incest avoidance for fathers. Physical proximity was not associated with incest propensity or disgust toward incest. Less disgust toward incest, however, was found to be associated with more incest propensity. These results indicate that physical proximity may not be a reliable kinship cue used by fathers to inform incest avoidance, but that disgust toward incest may still be a proximate mechanism that facilitates incest avoidance among fathers using kinship cues other than physical proximity.