Hormonal changes related to puberty may influence children’s development of preferences for certain facial features, suggesting an evolutionary basis for some aspects of human ideals of attractiveness, according to the findings of a study published in Evolution and Human Behavior.

Previous studies have shown that adults tend to rate human faces as more attractive when they have certain traits. These traits include symmetry (the left and right sides of the face mirror one another), averageness (facial features resemble a group composite, rather than being distinctive), health (no signs of sickness), and femininity (features are softer and proportioned more like the average woman’s than the average man’s).

Psychologists believe that innate preferences for these traits developed evolutionarily because they signal fertility and good health, and therefore help identify good potential mates. Infants and young children do not show preferences for these traits.

A new study of 346 British children aged 4 to 17, headed by Lynda Boothroyd of Durham University, was designed to discover at what age facial preferences develop. Children in the study were shown computer images of adult faces that were generated to have different levels of symmetry, averageness, health, and femininity. The children chose which faces they liked the most.

The youngest children did not have facial preferences related to any of these dimensions. By age 9, children’s preferences began to reflect adult patterns for symmetry, averageness, and health, but these preferences were weaker than those seen in adults. Preferences for femininity appeared only among late adolescents, and then only among girls.

The children’s stage of development in puberty was also measured to see if preferences develop due to the hormonal changes that happen during these ages. Only the changes in preference for facial symmetry corresponded with stages of puberty. Preferences for facial averageness, health, and femininity increased with age, but not in a way that corresponded with progress through puberty.

Researchers conclude that it is likely that changes in facial preferences are prompted by increases in the hormones DHEA, testosterone, and estrogen that occur before and during puberty. These changes prepare the brain to identify desirable mates as the body prepares to engage in reproduction.

“In summary, the results of the present study show that preferences for specific facial traits that adults deem attractive are not present in early childhood and develop in an apparently non-linear manner which is consistent with the proposition that early adrenal hormones may facilitate the activation of specific facial preferences,” the researchers said.

To prove that hormonal changes are responsible for the development of facial preferences, the next step for researchers is to measure children’s hormone levels. If hormonal changes can be directly linked to changes in the features people find attractive, it will provide strong evidence that our ideals of facial beauty have a basis in evolutionary biology.