How did the myth arise?

It arose as a way of explaining why dreadful things happened, such as people getting sick and dying.
As in many origin myths, man had lived in a world without worry – until this jar / box was opened, which contained ills for mankind. Zeus knew that Pandora’s curiosity would mean that she could not stop herself from opening it, especially when he had told her that she must not do so!

Many other myths also explain the ills of the world by saying they are caused by human disobedience of a god’s instructions.

(Though some versions of this story say that the box was a real gift and the box held good things for mankind, which Pandora let escape from the box, and fly away forever, only catching Hope.)

Even Hope itself has been argued about by scholars – not everyone agreeing that it is a great good – that maybe Zeus meant it as an evil also – otherwise it would not have been in a jar of evil. Others believe that Zeus may have relented a little, and put Hope in to help mankind through the hard times that the other ‘gifts’ would bring.