Back in the stone age, dogs meowed.  The dogs didn't like their meows, so they went to the wise dog, Spunky.  The dogs asked the wise dog, "Oh wise dog, will you please change our meows to a different sound so the felines will stop calling us copycats?"

Wise Spunky replied back to the dogs as he looked at his magic eight ball, "In the future there will be dog pounds, and try to get caught and they will teach you how to make a new sound."

So at the pound an old man came to visit all the dogs.  He hypnotized a dog to look at a tree and say what is covering the tree.  The dog said, "Bark!!"

So when the future finally came, all of the dogs tried to get the dog catcher to bring them to the pound.

The other dogs heard the bark and liked the sound of it.  Soon all the dogs were barking, they made so much noise the dog catcher let them go free so they would stop barking.  And from this day on, dogs bark!