God created the Mule, and told him," You are the Mule. Work constantly from dust to dawn, carrying heavy loads on your back. You will eat grass and lack intelligence.You will live for 50 years."
The Mule said, " To live like this for 50 years is too much. Please give me no more than 20."
And it was so.
Then God created the dog and told him," You are a dog. You will hold vigilance over the  dwellings of the Man, to whom you will be his companion. You will eat his table scraps and live for 25 years."
The dog responded," Lord, to live for 25 years as dog  like that is too much. Please, give me no more than 10."
And it was so.
God created the Monkey and told him," You are the Monkey,  shall swing from tree to tree, acting like an idiot. You will be funny. You shall live for 20 years."
The monkey said," Lord,  to give 20 years as the clown of the world is too much. Please give me no more  than 10."
And it was so.
Then God created the Man and told him," You are the only rational being that walks the earth. You will use your intelligence to have the mastery over the creatures of the world. You will dominate the earth and live for 20 years."
The Man responded," Lord, to  be the Man for only 20 years, is too little. Please give me 20 years, the mule ,refused, 15 years, the dog relinquished, and 10 years, the monkey rejected.
And God made the Man to live 20 years as a man, then marry and live for 20 years like the Mule, carrying heavy loads on his back. Then he is to have children and live for 15 years as a dog, guarding his house and eating the leftovers after they empty the pantry. Then in his old age, to live for 10 years as the Monkey,  like an idiot to amuse  his children."
And it is so.