Don't underestimate the importance of the oft-scorned nipple. They are teaching us something interesting about human evolution.
Evolutionary biologists believe that functional parts of the body – like the ear, nose, or brain stems – have low variation from person to person regardless of different shapes and sizes. Nipples, however, are considered high variation.
Back in 2008, Dr. Kim Wallen led a study published in the journal Evolution & Development and wrote:
Evolutionary researchers have sometimes taken findings of low variation in the size or shape of a biological feature to indicate that it is functional and under strong evolutionary selection, and have assumed that high variation implies weak or absent selection and therefore lack of function.
Australian researchers stated that "Male nipples are regarded as a prototypical evolutionary by-product, a non-functional version of the functional female nipple."
In simpler terms, the major difference between genders is that female nipples serve a biological purpose: breastfeeding. Male nipples do not.
The 2008 theory suggests then, that female nipples should have less variation in contrast to their male counterparts which are more ornamental and serve no critical function.
To test that 2008 theory, the University of Queensland in Australia recruited 63 consenting female students as participants and scanned and measured their nipples, noting different variables including body mass index and chest circumference.
The research published in Adaptive Human Behavior and Physiology indicated that not only do female nipple sizes tend to be larger than average male nipples, but size variation between females was higher at 38% than the 25% variance calculated for men.
The results led authors to dismiss the former 2008 study, saying they "discredit previous studies that have taken relatively high size variability of a feature to indicate lack of functionality."
Some fellow research scientists posed completely different questions though.
The 2008 study also claimed that "the greater length variation of clitorises than of penises meant that the female orgasm is a nonfunctional byproduct of male orgasm."
However, lead researcher of the Australian study, Ashleigh Kelly, stated that variability doesn't consistently reflect functionality. The clitoris and penis assumptions might be a stretch based on the latest research findings.
According to Newsweek, the latest research refuted the 2008 theory when they found female nipples had a higher variable than their male counterpart.
Female nipples are functional as they are used in breastfeeding.
Therefore, the finding that females [sic] nipples are highly variable discredits previous studies that indicate variation in a specific feature indicates a lack of functionality.
The Queensland researchers concluded that future studies should not assume that variation in a body part was the result of natural selection.
But some people just couldn't get past that photo Newsweek chose.