God created various animals and assigned them different roles and lifespans. The mule was given 50 years but asked for only 20. The dog was given 25 years but requested 10 instead. The monkey was allotted 20 years but wanted just 10. When God created man and offered 20 years, man bargained for the extra years the other animals declined, to have a lifespan of 20 years as a man, 30 as a mule, 15 as a dog, and 10 as a monkey.