Abstract
Understanding how individuals identify their relatives has implications for theevolution of social behaviour. Kinship cues might be based on familiarity, butin the face of paternity uncertainty and costly paternal investment, other mech-anisms such as phenotypic matching may have evolved. In humans, paternalrecognition of offspring and subsequent discriminative paternal investmenthave been linked to father–offspring facial phenotypic similarities. However,the extent to which paternity detection is impaired by environmentally inducedfacial information is unclear. We used 27 portraits of fathers and their adult sonsto quantify the level of paternity detection according to experimental treatmentsthat manipulate the location, type and quantity of visible facial information. Wefound that (i) the lower part of the face, that changes most with development,does not contain paternity cues, (ii) paternity can be detected even if relationalinformation within the face is disrupted and (iii) the signal depends on the pres-ence of specific information rather than their number. Taken together, the resultssupport the view that environmental effects have little influence on the detec-tion of paternity using facial similarities. This suggests that the cognitivedispositions enabling the facial detection of kinship relationships ignore geneticirrelevant facial information