Why Do We Have Belly Buttons?

The video explains that belly buttons, or navels, are scars from the umbilical cord, which connects a baby to its mother for nutrients and oxygen before birth. After birth, the cord is cut, leaving a belly button. This process is similar in many mammals, but not in egg-laying animals like birds and reptiles, which don't have belly buttons as they aren't connected to their mothers by a cord.

What similarities exist between human belly buttons and those of other mammals?

What significance do belly buttons have for humans after birth?