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.
The Biomotion Lab at Queen’s University in Ontario is running an experiment to figure out what cues people use to tell the sex of a moving figure. You can help! Watch the line-and-dot animations they’ve created, and telling them whether you think each figure is a man or a woman.
Some sex differences, like facial hair or genital anatomy, are plain to see. But people also have hormonal and metabolic sex differences that aren’t so obvious, and those can change how diseases affect the body and how drugs work.
Male kangaroos and wallabies, like a lot of seemingly quiet grazing animals, get into knock-down drag-out fights over females. They obviously don’t have antlers or horns to spar with, but they’re perfectly willing to grapple rivals with their forelimbs and kick the crap out of each other with their big hind feet.