Researchers Debunk An Evolutionary Assumption Using Nipples

In the old mode of thinking in evolutionary biology, which takes an “if it ain’t broke, don’t fix it” approach to our features, women’s nipples, which serve a strong purpose, shouldn't vary as much as they do. The fact that women get such a mixed bag of nips across generations and individuals challenges this thinking.

In a study published in Adaptive Human Behavior and Physiology, researchers from the University of Queensland in Australia sought to test this assumption: features that vary a lot—such as female nipples—result from weak evolutionary selection, and features that are mostly the same across generations stay that way because they serve a strong evolutionary purpose.

To research how nips vary, they studied the nipples of 63 Australian undergraduate students, measuring the “nipple-areola complex,” including the circular colored area around the nip itself, as well as a variety of other factors, including bust circumference, body mass, and height. They also took the temperature of the room into account.

“We found that female nipples were significantly more variable than male nipples,” Ashleigh Kelly, lead researcher on the study, said in a press release. Male nipples were, on average, 36 percent the size of female nipples.

In case you didn’t know, men’s and women’s nipples are very different. Men get little decorative areolas that mostly stay the same. They don’t do anything. They’re there because evolution deemed them not harmful enough to leave behind, and not useful enough to adapt to do anything different. Women get nipples that vary wildly from person to person in size, shape and shade, are sensitive to arousal and temperature, and feed babies.

“Female nipples are functional as they are used in breastfeeding,” Kelly said. “Therefore, the finding that females nipples are highly variable discredits previous studies that indicate variation in a specific feature indicates a lack of functionality.”

These finding also debunk another evolutionary biology assumption: That the female orgasm is a nonfunctional byproduct of male orgasm, and that varying clitorous sizes doesn’t mean the clit is a useless evolutionary feature.

“Our findings serve to prevent others from designing studies based on incorrect assumptions about the relationship of variability with functionality or selection,” the researchers write in the study. Spread the good word.