Marianne Heijkoop and colleagues made these observations after surveying 90 Dutch parents with children aged between eight and nine years. They argue the findings provide tentative support for the evolutionary-based idea that men will be more motivated to invest in children who look like themselves than those who don’t. The theory is that men, unlike women, can never been wholly certain that a child is theirs, thus leading them to depend on cues, such as physical similarity, when deciding whether to invest in a given child.
The new findings support the idea that even today fathers are influenced by this innate tendency to invest more in children who resemble them. However, the cross-sectional methodology means that the case is far from closed. One alternative explanation for the results is that being emotionally closer to their children leads men to think their children resemble them more.
Incidentally, physical resemblance had no association with the closeness of mothers to their children, but personality similarity did.
Marianne Heijkoop, Judith Semon Dubas, Marcel van Aken (2009). Parent-child resemblance and kin investment: Physical resemblance or personality similarity? European Journal of Developmental Psychology, 6 (1), 64-69 DOI: 10.1080/17405620802642306