Infants born out of wedlock who look like their father are healthier one year after birth, according to an analysis of the Fragile Family and Child Wellbeing study.
The analysis says when a child resembles its father, it drives the father to spend more time engaged in positive parenting. One extra day per month of time investment can benefit the child's health.
The study states these results make sense when aligned with evolutionary theory, which predicts that parents will provide preferential care to related children in order to further their own genealogy. It goes on to say doubtful men can use a child's resemblance as a sign of genetic relatedness.
This is based on 715 families in which babies lived with their mother in big cities between 1998 and 2000. To read the full analysis, click here.