Here's why:
* Bellybuttons are the scar left behind after the umbilical cord is cut. This cord was essential for providing nutrients and oxygen from the mother to the developing baby in the womb.
* Only mammals give birth to live young and have a placenta. This means only mammals need an umbilical cord and therefore have bellybuttons.
So, the next time you see a cat, dog, or even a human, remember that they all have a bellybutton! 😊