Expert: John Locke - 9/5/2006

Question
Hello,
I've been watching a show called Kyle XY.  In short, it's about a boy with amnesia and no belly button, but he's extremely intelligent.  A friend and I were discussing the belly button issue.  We were wondering if common animals (ie cats, dogs, horses, etc.) have belly buttons.  I believe they're mammals and therefore should have been connect to a placenta, but I'm not positive and have never seen one on any of them.  Also, can you think of any circumstances wehre a person wouldn't have a belly button?  Thank you.

Answer
Thanks for using AllExperts, Adam.

All placental mammals have some form of a belly button--although it doesn't always look like those on people. For that matter, most animals don't have belly buttons (also called navels, which I will do here for
simplicity) that look anything like those of humans; in other placental mammals, like dogs, cats, and monkeys, the umbilical usually looks just like a small, hairless scar.
This is often hard to see, of course, because most other placental mammals also have considerable body hair, but it's still located on the lower abdomen, regardless of the creature. You are right in your suspicions: any mammal that developed while connected to an umbilical cord will wind up with some form of mark, scar, indentation, etc., where the umbilical cord was attached.

To give you an idea of what it looks like in other animals, I've found a picture at the very bottom of the page here:

Be forewarned that there are images of a ewe giving birth on this page, which you might find unpleasant.

http://bedford.extension.psu.edu/Agriculture/Lessons/Process%20of%20Lambing.htm

As to your second question, I am not aware of any cases in which a person would be born without a navel. It is possible to remove one's navel via plastic surgery, though I'm not aware of any cases of that occurring either (although there is a popular form of plastic surgery that involves reshaping one's navel--umbilicolasty). Occasionally, navels are removed during photo retouching for magazine covers and the like, resulting in a person without a navel--though by strictly electronic means!