Men need bigger noses because they tend to have more muscle—meaning they need more oxygen, a new study suggests. Researchers followed the growth of 18 women and 20 men from age three to past 20. While kids' nose sizes weren't much different between sexes, male noses started getting bigger around the time of puberty. That's also the period when males start to use more oxygen and energy than females, LiveScience reports. Lean muscle is responsible for some 95% of male weight gain during puberty, compared to 85% of female weight gain, according to earlier studies.
"After puberty ... males tend to have larger noses because more of the male body is made up of lean muscle tissue that's metabolically more expensive," says the lead author, per National Geographic. In the study, men's noses were some 10% larger than women's. This could also explain why Neanderthals, who were bigger than we are, had big noses. (In other gender-science news, a study finds that the male-defining Y chromosome isn't fully needed for reproduction.)