Navel-gazing may serve a useful purpose, after all. People may use belly button beauty to assess the fitness of a potential mate, according to Aki Sinkkonen of the University of Helsinki, Finland.
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"I was younger than nowadays, and some of my friends were discussing how some women have a beautiful umbilicus or navel," Sinkkonen told Discovery News. "I was thinking, 'How is this possible? If this is scar tissue, how is it possible that it can be beautiful?"
Indeed, the navel is often cited as a textbook example of a useless body part. But Sinkkonen, who published his idea recently in the FASEB Journal, said there is plenty of evidence that there is more to it than that.
For instance, in many mammals, the navel forms a tiny, asymmetrical scar. But in humans, it is a visible and significant mark. Many cultures draw attention to it in art, Sinkkonen noted, and some wealthy people pay plenty to have their navel's appearance enhanced.
Sinkkonen pointed out a study by Charles Puckett and colleagues of the University of Misouri, which asked people to choose from a number of navels the one that was most attractive. The subjects agreed: the best-looking navels were vertically oriented with a T-shape.
Those with particularly large belly buttons, or with any sort of protrusions — sorry, outies — or distortions, received lower scores.
The fact that there is consensus about which navels are most attractive supports the idea that there's an advantage to finding a certain type of navel attractive, Sinkkonen said.
That advantage should be how fit a person is to mate, but the reason certain belly buttons are more attractive may depend on several aspects of an individual's circumstances. Genetics, health at birth and current health all can play a role in the navel's appearance, Sinkkonen said.
"You cannot fake a good-looking umbilicus, so if you do not have enough fat or if you have too much fat, it doesn't look good. If your mother was sick when she was pregnant, it may not be good."
Sinkkonen has plans to gather evidence for his hypothesis. In particular, he plans to study which mammals have a visible navel and whether that relates to how much fur they have, and therefore how visible the navel is as a signal to potential mates.
"It makes a lot of biological sense," said Gerald Weissmann of New York University School of Medicine and a FASEB editor. "I think it's a novel original contribution; it's a fertile idea."
However, Sinkkonen assured, "If you have an umbilicus that you think is ugly, it does not necessarily mean that your genetics is bad."
© 2012 Discovery Channel