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Abstract

Kin recognition is a key ability which facilitates the acquisition of inclusive
fitness benefits and enables optimal outbreeding. In primates, phenotype
matching is considered particularly important for the recognition of patrili-
neal relatives, as information on paternity is unlikely to be available via
social familiarity. Phenotypic cues to both paternal and maternal relatedness
exist in the facial features of humans and other primates. However, theoreti-
cal models suggest that in systems with uncertainty parentage it may be
adaptive for offspring to conceal such cues when young, in order to avoid
potential costs of being discriminated against by unrelated adults. Using
experienced human raters, we demonstrate in a computer-based task that
detection of parent–offspring resemblances in the faces of rhesus macaques
(
Macaca mulatta
) increases significantly with offspring age. Moreover, this
effect is specific to information about kinship, as raters were extremely suc-
cessful at discriminating individuals even among the youngest animals.
To our knowledge, this is the first evidence in non-humans for the
age-dependent expression of visual cues used in kin recognition.