Parsing the Mechanisms Underlying Ingroup Facial Resemblance

People prefer to form relationships with people like themselves—a tendency that extends even to facial appearance, resulting in groups whose members look alike. Here, we investigated the mechanisms underlying homophilic resemblance using facial photos of fraternity/sorority members from two time points: before joining the group and after belonging to the group for three years. Analyses of both subjective trait impressions and objective face-shape measurements revealed that not only did group members look alike, they resembled one another even before joining the group. Moreover, photos of potential fraternity recruits revealed that facial appearance predicted both the group that individuals sought to join and the group’s likelihood of accepting them. Individuals, therefore, seek to join groups consisting of people who look like them, and the groups preferentially accept new members who resemble those already in the group. This bidirectional preference for homophily likely perpetuates intragroup homogeneity, suggesting potential implications beyond appearance.

Same father, same face: Deep learning reveals selection for signaling kinship in a wild primate

Many animals rely on facial traits to recognize their kin; however, whether these traits have been selected specifically for this function remains unknown. Using deep learning for face recognition, we present the first evidence that interindividual facial resemblance has been selected to signal paternal kinship. Mandrills (Mandrillus sphinx) live in matrilineal societies, in which females spend their entire lives not only with maternal half-sisters (MHS) but also with paternal half-sisters (PHS). We show that PHS have more differentiated social relationships compared to nonkin, suggesting the existence of kin recognition mechanisms. We further demonstrate that facial resemblance increases with genetic relatedness. However, PHS resemble each other visually more than MHS do, despite both kin categories sharing similar degrees of genetic relatedness. This paternally derived facial resemblance among PHS indicates selection to facilitate kin recognition. This study also highlights the potential of artificial intelligence to study phenotypic evolution.

Who Gains More? The Relationship Between Parenthood and Well-Being

Two studies were conducted to explore the effect of parental sex on well-being due to parenthood. Study 1 analyzed the sixth wave of the World Values Survey data. The results indicated that parents were happier than their respective childless peers. However, the effect of motherhood was significantly higher than that of fatherhood. Furthermore, Study 2 analyzed the data from 354 single-child parents in China. The results showed that perceived parent–child facial resemblance moderated the sex difference in well-being. Specifically, in the high parent–child facial resemblance group, both fathers and mothers showed high levels of well-being; however, in the low parent–child facial resemblance group, the well-being level of mothers was higher than fathers. These results supported the renovated pyramid of needs and the hypothesis of paternal uncertainty.