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EVolunteer biologists think a lot about nipples, but they are also puzzled. Why are all of different shapes and sizes? This posed such an enigma that a team from the University of Queensland Australia compared the nipple size of 33 men and 30 women and published their findings in the review. Adaptive human behavior and physiology, suggesting that size variation challenges a basic evolutionary theory.
For the vast majority of body parts, there is a trend in evolutionary biology: "Use it or lose it." Many cavernicolous fish, for example, have independently developed blindness over generations, suggesting that this is the only way in was a benefit to not wasting valuable energy on a useless organ. Conventional evolutionary wisdom suggests that, as happens, the variation in eye characteristics in a population of these fish would decrease. "Basically, if there is genetic variation to begin with, and natural selection favors a particular variant (increased survival for this type of trait, for example), genetic variation will decrease, other variants becoming less frequent or disappearing "explains Nolan Kane, Ph.D., assistant professor in ecology and evolutionary biology at the University of Colorado Boulder not associated with this study, says reverse. This idea was thought to relate to the nipples, but maybe not for long.
According to this logic, the female nipple, which has a clear evolutionary goal (to feed the babies), should have very little variation – at least compared to the male nipples, which the study authors ruthlessly describe as "non-functional ". So, when the team spent an afternoon measuring the size of a female nipple, they thought that they would find less variation – in short, a nipple sharpened by natural selection. Instead, they found more variation in female nipple size than in male counterparts. These results implied that this genetic variation was still there, even though, according to conventional theory, it should not have been.
"Female nipples are functional because they are used in breastfeeding," said lead author Ashleigh Kelley, Ph.D. in one version. "Therefore, the finding that females' nipples are highly variable discredits previous studies that indicate the variation of a specific characteristic indicates a lack of functionality."
The conclusion of this study actually has less to do with nipple size and more with the way we interpret a fundamental theory of evolutionary biology. The lack of variation alone, the researchers find, should not be how we judge whether a trait is advantageous. This is a potential misuse of the theory that Kane also warns against: "Just look at the variation that exists for any trait today, as the authors demonstrate in this study, "he concludes.
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