Hormone surges at puberty trigger a lot of physical changes in both men and women, morphing child-bodies into adult forms. Genitals, hips, and muscle mass change, obviously — but so do faces. A new study suggests those facial changes are primed to happen by the presence of testosterone in utero.
Andrew Whitehouse and colleagues at the University of Western Australia used umbilical cord blood collected as part of a long-term cohort study, and asked 183 of the former newborns, now in their early twenties, to visit the lab to have 3D infrared images made of their faces. After analysing the locations of a variety of facial landmarks, including points on the nose, lips, chin, eyes, and forehead, the team compared the relative masculinity or femininity of each face to the testosterone concentration inside that person's cord blood (and for 85 of the 97 men in the study, the testosterone in their adult blood as well).
In a new paper in Proceedings B of the Royal Society of London, they report that the people with more masculine-looking faces, both male and female, also had higher levels of testosterone inside their cord blood. When they ran the same test on the men who provided blood as adults, they found that adult levels of testosterone didn't have any relationship to the masculinity of facial features.
The authors stress that they have no data about what happened to their subjects during puberty, when testosterone levels in males can surge to levels 20 or 30 times higher than in females. But this study is another clear sign that the hormones we make before we're born affect the way we'll look years later.