Whether you have an innie or an outie, pretty much all of us mammals have a belly button. But before you had a belly button, there was actually a different bit of anatomy in its place.
While you were still growing inside of your mother, a small, bendy tube on your tummy connected the two of you. This tube is how you got pretty much everything you needed to grow before you were born into the world, said WSU nursing instructor Gina Cronrath.
See the full answer at the Dr. Universe website.