Abstract
Human fathers face paternity uncertainty and are expected to use cues of relatedness to adjust their investment. So far, the main cue hypothesised to account for paternity assessment is facial phenotypic resemblance between a father and his child. However, previous studies showing a discriminative paternal investment either relied on fathers' perceptions of resemblance (which differs from actual resemblance, as perceived resemblance could be socially biased), or manipulated facial resemblance. In this study, we investigate in a real-life situation, whether (1) the perception of child facial resemblance and (2) the likelihood of parental investment were predicted by actual facial resemblance to self, for both parents. The actual facial resemblance of 79 French children was quantified by testing external judges. Data on ascription of resemblance and parental investment were collected in private for each parent. First, ascription of facial resemblance was found to be consistent between the two parents and to match actual resemblance to the father. Second, emotional closeness as reported by fathers, but not by mothers, was found to be predicted by actual facial resemblance to self. This suggests that paternity uncertainty has favored the use of facial phenotype matching in fathers.