Seems that when the Lord was creating the world, He called man over and bestowed upon him twenty years of normal sex life. Man was absolutely horrified...

"Only twenty years of normal sex life?"

Yet, the Lord was adamant and insisted that Man could have no more than twenty years of normal sex life.

Then, the Lord called the monkey and gave him twenty years.

"But, I don't need twenty years, "protested the monkey.

"Ten years is plenty for me."

Man spoke up eagerly, "Can I have the other ten years?"

The monkey graciously agreed.

Then, the Lord called the lion and gave him twenty years. The lion, like the monkey, only wanted ten years.

Again, man spoke up, "can I have the other ten years?"

The lion graciously agreed.

Then, along came a donkey and he too was given twenty years. But, like the others, ten years was more than sufficient. Once again, man pleaded, "can I have the other ten years?"

And so, it all makes perfect sense now... Man has twenty years of normal sex life, ten years of monkeying around, ten years of lion about it and ten years of making an ass of himself.