3.5 Attraction, beauty, and signals of fitness

"Beauty is in the eye of the beholder" is half true. Much of attraction is culturally variable, but a surprising core is universal — and the universal core consists of cues that signaled health, fertility, and genetic quality.

Symmetry

Fluctuating asymmetry — small random departures from bilateral symmetry — tends to increase with developmental stress, disease, and mutation load. Symmetry is therefore an honest cue of developmental stability, and across species and cultures, more symmetric faces and bodies tend to be rated more attractive.

Averageness

Counterintuitively, faces that are average — close to the mathematical mean of the population — are rated as more attractive than unusual faces. Composite faces made by averaging many individuals are consistently judged beautiful. Averageness may signal genetic diversity, developmental normality, and the absence of harmful mutations.

Honest signals and hormone markers

Some attractive features are hormone markers: estrogen-dependent features in women and testosterone-dependent features in men (a strong jaw, for instance). Because high testosterone is immunosuppressive, only a healthy male can "afford" to display strongly masculine features — making them an honest, handicap-style signal of quality.

A grounding example

Judith Langlois demonstrated that the preference for attractive faces is present before culture could install it: infants only a few months old look longer at faces adults rate as attractive than at faces rated unattractive. Babies have not learned any beauty standard from magazines or media, yet they already prefer the same faces adults do. This early, pre-cultural agreement points to an evolved face-evaluation mechanism tuned to cues of health and quality.