God created the donkey and told him: you will work tirelessly from sunrise to sunset, carring heavy bags on your back, you'll eat grass, you will not have intelligence and you will live 50 years. You will be a DONKEY!
The donkey answered: I'll be a donkey, but living 50 years is too much, give
me only 20 years. And God gave him 20 years.
God created the dog and told him: You will look after the men house, you will
be his best friend, you will eat whatever they give you and you will live 25
years. You will be a DOG!
The dog answered: God, living 25 years is too much, give only 10. God gave
him 10 years.
God created the monkey and told him: You will jump from branch to branch, you
will do silly things, you will be amusing and you will live 20 years.
The monkey answered: God, living 20 years is too much, give me only 10 years.
And God agreed.
Finally, God created man, and told him: You will be Man, the only rational
being on this earth, you will use your intelligence to control other animals,
you will dominate the world and you will live for 20 years.
The man answered: God, I'll be man, but living 20 years is not enough, why
don't you give me the 30 years that the donkey refused, the 20 years that the
dog did not want and the 10 years that the monkey refused.
That was what God did, and since then...
Man live 20 years like a man, then he enters adulthood and spends 30 years
like a donkey, working and carrying the load on his back. Then when his children
leave home, spends 15 years like a dog, looking after the house and eating
whatever is given to him. Then he gets into retirement, and spends 10 years like
a monkey, jumping from house to house or from children to children, doing silly
things to amuse the grandchildren.