A young chimp watches how his mom cracks nuts. She grabs a rock. He grabs rock. She takes a nut. He takes a nut. She carefully cracks open the nut to get the treat inside. He tries stepping on it.
It will be a while before this young chimp learns how to crack nuts on his own. He has lots of time to practice, though. Big brains take a lot of time and energy to develop. Youth is also the time for primates to learn useful skills for surviving as adults.