The origins of the appearances of anger and fear facial expressions are not well understood. The authors tested the hypothesis that such origins might lie in the expressions' resemblance to, respectively, mature and babyish faces in three studies. In Study 1, faces expressing anger and fear were judged to physically resemble mature and babyish faces. Study 2 indicated that characteristics associated specifically with babyishness are attributed to persons showing fear, whereas characteristics associated with maturity are attributed to persons showing anger. In Study 3, composite faces were used to minimize the possibility that the attributions were based on associations to the anger and fear emotions alone rather than to the physical resemblance of the expressions to static facial appearance cues. These results suggest that fear and anger expressions may serve socially adaptive purposes for those who show them, similar to the social adaptations associated with a babyish or mature facial appearance.