Babies can't stay babies all their lives!
They have to grow up! When first born, human babies are completely dependent on their parents for everything - food, water, shelter, clothing.
As babies grow into children and adolescents, humans are still dependent on their parents for many things - they have a lot of growing up to do, and don't become independent until they reach the age of about 18 when they go to college or move away from home.
Think of all the things that your parents still do for you.
They feed you, house you, act as your taxi service, and still give you pocket money!!!
(Aren't they great!!!)
Compared with most young animals humans have a very cushy life! Birds are encouraged to leave the nest as soon as they can fly and gather food for themselves. And most animals that live in the sea don't have any contact with their parents at all - they have to survive by themselves from day one.
So how do we grow? Like other mammals, humans grow at a fairly steady pace until they reach adulthood. Every day as they get older their bodies are changing. Their skeleton grows with them, each bone getting bigger over time.
The pictures below are trying to show you how bones grow. It is not completely accurate, as bones change shape as well as size, but you get the general idea.
Move your mouse over the pictures to see what's going on!
But this steady, constant growth does not happen in all animals. Arthropods - insects, spiders, crabs and other animals with external skeletons - grow in a very different way. The problem with having a hard outer skeleton means that you will grow out of it - just like you grow out of clothes. To get any bigger, animals like crabs and spiders have to shed their skeleton and grow a new one!