I wasn't sure how far back in history this gesture went. But now that you mention it I do recall an incident in "The Twelve Caesars" which is a historical account of the lives of Julius Caesar and the first 11 Roman emperors.
Originally Posted by Etzelnik
This excerpt is from the reign of Augustus:
Hylas, the pantomimic actor, was openly scourged in the atrium of his own house, because a praetor complained about him; while Pylades was not only expelled from the City, but banished from Italy, for directing the whole audience’s attention to a spectator who was hissing him, by giving him the finger.
So by the time Galileo's remains were placed in a monumental tomb in 1737 and the finger was removed by Gori, this gesture had been around for at least over 17 centuries.
Since I already brought it up, I recommend "The Twelve Caesars" by Gaius Suetonius Tranquillus (or just plain Suetonius).
As histories go it's very gossipy. A lot of the good stuff in "I, Claudius" comes from this second century book.