Talk about navel gazing! Scientists have been eyeing innies and ogling outies for years now, and some of their findings are pretty astonishing. So if you think your navel has nothing to do but sit there and collect lint, check out(ie) our list of eight surprising belly button facts.
You'll be amazed at just how much your little umbilicus has to say about you.
1. You're a hottie.
Some belly buttons are sexier than others. And that's been backed up by science. University of Helsinki researcher Aki Sinkkonen says we tend to like navels that are T-shaped or oval and vertical, with a little hooding, LiveScience reported in 2009. Outies? They get a thumbs down. So do innies that are too deep.
What's more, Sinkkonen says a woman's navel actually signals her reproductive fitness. "I suggest that the symmetry, shape, and position of umbilicus can be used to estimate the reproductive potential of fertile females, including risks of certain genetically and maternally inherited fetal anomalies," he wrote in The FASEB Journal, according to LiveScience.
2. But you're no Karolina Kurkova.
All placental mammals, including humans, have a belly button--because all of us were once attached to our mothers' bodies via an umbilical cord. Supermodel Karolina Kurkova reportedly doesn't have one, but only because it was removed during an operation she had in infancy. So if you have a navel down there, rest assured you can't be Karolina.
Another celebrity rumored to have lost his belly button to surgery is Alfred Hitchcock. But it's not clear whether the rumors are true.
Karolina Kurkova walks the runway in Milan, Italy on February 19, 2013. (Stefania D'Alessandro/Getty Images)
3. You're a hairy dude.
Just about anyone can have belly button lint. But research has shown that the ladies are a lot more likely to be lint-free than the gents. According to a 2009 article in The Telegraph, an Australian study that looked at lint samples from 5,000 people resulted in a not-too-flattering profile for lint-challenged individuals: "a slightly overweight middle-aged male with a hairy abdomen." Why would that be? Because lint is created in part by the abrasive action of belly hair on clothing fibers.
4. You bought new undershirts.
5. You're pregnant.
Innies tend to stay innies, outies outies. But pregnancy can cause navels to change shape. "The expansion of the abdomen can cause some 'innie' belly buttons to pop out and become outies," Dr. Karen Marie Jaffee, an obstetrician-gynecologist affiliated with University Hospitals of Cleveland, told Everyday Health. "But most often, there is not much change in the structure itself." After birth? The belly button often returns to its usual shape.
6. You're wicked fast.
The position of your belly button helps determine how fast you run or swim. That's the surprising takeaway from a study by Duke University researcher Andre Bejan. Given two runners or swimmers of the same height, he told AFP in 2010, "what matters is not total height but the position of the belly button." And that may explain why so many elite runners are of African ancestry. People of West African origin tend to have longer legs than people of European ancestry, he said, which means their belly buttons are about 1.8 inches higher than those of whites.
7. It's crowded in here.
Human skin is teeming with bacteria, and what's true for other parts of the body is also true for the belly button. Believe it or not, researchers have found 1,400 different strains of bacteria lurking in the human navel, according to the Toronto Star. And don't forget about the lint!
8. You're in the mainstream.
Got an innie? You're in the majority. Ninety percent of humans have innies.