Of course everyone knows there's a reason for puberty, but I see a lot of guys with what I call half-ass puberty. They lack muscle tone, a defined jaw, a noticable nose bone, or even facial hair. It makes me wonder if they are genetically weak, not to sound like an elitist. Women subconsciously read male faces by judging facial features that potentially reveal fitness (defined as an individual’s ability to survive and to produce viable offspring). Of the facial characters that women could find particularly informative, Evolutionary Psychologists have predicted that characters linked to sex hormones (e.g. testosterone) may be particularly good indicators of male fitness. There are a couple of reasons for this prediction: Testosterone directly affects the growth of certain facial features, and of the gonads. Testosterone is part of the reason why boys’ faces change shape during puberty (when testosterone levels are high). Testosterone is believed to suppress the immune system and so impose a “handicap” on individuals with high testosterone. If there is a cost to having high testosterone, then perhaps only the “best” males can carry this cost. Poor quality males cannot cope with such high levels of testosterone. Therefore, levels of testosterone in the male face may be an “honest” indicator of fitness.