The algebra of fatherhood

Whereas women are sure of their biological maternity, men can never be fully certain of paternity and instead need to rely on indirect cues to assess whether they are likely to be father of their putative children. According to the psychological literature, men commonly use the information on the resemblance of offspring to self as an indicator of genetic relatedness. It seems, however, that in the absence of such a resemblance, similarity between a mother and a child might be important, because a man has additional reason to doubt his own biological paternity when the child is dissimilar to his partner. This assumption has been verified in two empirical studies.