It’s nose comparison: Men’s noses really are larger than women’s, and now we know why. On average, the difference is about 10 percent in sniffers of European heritage, reports a new study from the University of Iowa.

Males typically need more oxygen because they have more lean muscle mass. A larger nose can provide extra oxygen to promote muscle tissue growth and maintain muscles.

PHOTOS: Most Popular Plastic Surgeries

The differences start appearing around age 11, when puberty kicks in. 

The study also sheds light on why modern humans have smaller noses than, say, Neanderthals, who had more muscle mass and needed larger noses to maintain that muscle.

“So, in humans, the nose can become small, because our bodies have smaller oxygen requirements than we see in archaic humans,” Nathan Holton, an assistant professor at the University of Iowa, said in a press release. The paper was published in the American Journal of Physical Anthropology.

NEWS: New Nose Is Grown On Man’s Forehead

The study tracked the nose size of 38 people of European descent, from age 3 until their mid-20s. The researchers expect the findings will hold up across other cultures and races, but more research is needed.

“Even if the body size is the same,” Holton said, “males have larger noses, because more of the body is made up of that expensive tissue. And, it’s at puberty that these differences really take off.”

Male noses grow larger than female noses beginning at puberty. Image courtesy of the University of Iowa College of Dentistry.