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UBC Theses and Dissertations

Three theories for facial paedomorphosis in human evolution and the preference for facial underdevelopment Wehr, Paul Arthur


Human faces are relatively underdeveloped compared to both ancestral human populations, and to other modern primates. Several researchers have noted a relationship between facial juvenilization and facial attractiveness in humans. Three theories were developed to account for what seems to be the co-evolution of underdevelopment in human morphology and mating preferences. In the baby-face overgeneralization hypothesis, facial underdevelopment stimulated altruistic behaviour and inhibited aggression. The youthful mimic hypothesis proposes that underdevelopment mimicked facial cues associated with youth and fertility. In the big brain hypothesis, facial underdevelopment was a necessary antecedent to brain expansion and human cognition. Predictions were generated from each hypothesis with regards to how the juvenilization preference would change as a function of context, mating strategy, and sex. Composite faces were manipulated to appear either more or less underdeveloped (juvenilized). Results indicated that the preference for juvenilized features was stronger in a mating context, stronger for male judges evaluating female targets, and stronger for a short-term mating strategy. Results were most supportive of the youthfulness hypothesis, but some support was also found for the big brain hypothesis. While the youthfulness hypothesis may explain the preference for facial underdevelopment, the big brain hypothesis might provide a more satisfactory explanation for the evolution of facial underdevelopment.

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