Parents are often unable to discriminate their own infants from other parents' infants, and in humans it is appreciated that infants do not necessarily resemble their parents. A number of factors might cause the infants of a species to have a similar appearance, including requirements for camouflage or signalling, the biomechanics of birth in viviparous species, or even the development of so-called ‘releasing stimuli’. Alternatively, a simple population genetics model shows that some aspects of neonatal appearance may arise as adaptive strategies on the part of infants actively to conceal the identity of their parents, especially of their father. Concealing paternal identity is advantageous as a strategy to avoid paternal neglect, abuse, or infanticide when the ‘domestic father’ is not likely to be the ‘biological father’. The model reveals that ‘anonymity’ as a neonatal strategy can be adaptive in a wide range of mating systems, because infants are expected to resemble their fathers only if the ‘domestic father’ is also the ‘biological father’ a high proportion of the time: even small amounts of paternity uncertainty are sufficient to select against parent–infant resemblance. The available empirical evidence suggests that human infants have been selected not to resemble their parents. However, if paternity certainty is sufficiently high in some groups for resemblance to evolve, the model predicts that offspring will resemble their fathers but not their mothers, consistent with the results of one recent study.