Ascription of resemblance of newborns by parents and nonrelatives

Abstract

It has been hypothesized that human females ascribe the resemblance of their infants to the father or his relatives to promote assurance of paternity. Assurance renders fathers more likely to invest in and less likely to harm mothers and their children. Other studies have documented a bias toward the father's side of the family when mothers ascribe the resemblance of their infants. We test if this bias extends to newborns (1–3 days old) and if such bias reflects actual resemblances. This was done by noting the responses of mothers when asked whom they thought their newborns resembled and by comparing those responses to resemblances ascribed by unrelated judges. During in-hospital visits, mothers were significantly more likely to ascribe resemblance to the domestic father than to themselves. This bias was exaggerated in the presence versus absence of domestic fathers. Yet, judges matched photographs of these mothers to their newborns significantly more frequently than they matched domestic fathers to newborns. Thus, the bias in how mothers remark resemblance does not reflect actual resemblance and may be an evolved or conditioned response to assure domestic fathers of their paternity. The low rate with which newborns are matched to fathers may be biologically significant. Concealment of paternity may be favored when suspicion of cuckoldry leads fathers to abandon or harm newborns. Genomic imprinting is one mechanism by which resemblance of newborns could be biased toward mothers. We suggest that on average females benefit from concealed paternity even if cuckoldry is rare provided that their verbal ascriptions of resemblance are effective in assuring domestic fathers of their paternity.