Previous research indicates positive effects of a person’s attractiveness on evaluations of opposite-sex persons, but less positive or even negative effects of attractiveness on same-sex evaluations. These biases are consistent with social motives linked to mate search and intrasexual rivalry. In line with the hypothesis that such motives should not become operative until after puberty, 6- to 12-year-old participants (i.e., children) displayed no evidence for biased social evaluations based on other people’s attractiveness. In contrast, 13- to 19-year-old participants (i.e., adolescents) (...) displayed positive and negative attractiveness biases toward opposite- and same-sex targets, respectively. Moreover, these biases increased with the age—and thus the reproductive relevance—of the targets being evaluated. Findings corroborate the relevance of mating-related motives for social judgment and illustrate how such biases can grow during human development. At a broader conceptual level, this research demonstrates the utility of investigating proximate social judgment processes through the lens of adaptationist thinking. (shrink)