On the first day, God created the dog and said:

'Sit all day by the door of your house and bark at anyone who comes in or walks past. For this, I will give you a life span of twenty years.'

The dog said: 'That's a long time to be barking. How about only ten years and I'll give you back the other ten?'

So God agreed.

On the second day, God created the monkey and said:

'Entertain people, do tricks, and make them laugh. For this, I'll give you a twenty-year life span.'

The monkey said: 'Monkey tricks for twenty years? That's a pretty long time to perform. How about I give you back ten like the Dog did?'

And God agreed.