What are the origins of the middle finger gesture?

The origins of the gesture universally referred to as "The Finger" are unknown, although its use as an obscenity can be dated at least as far back as 419 B.C. when the playwright Aristophanes writes about it in his comedy "The Clouds." However, the expression may be even older, since experts point out that male squirrel monkeys in South Africa also make a similar gesture with their penises.

This ancient insult is known as a phallic gesture in some circles, and it was called the offensive finger or digitus impudicus by the Romans. The finger itself is said to represent a penis, while the surrounding knuckles form two testicles. Many find the gesture to be one of the worst nonverbal insults.