Gears were already used in India as early as 2600 BC, Aristotle described gears in his lifetime - about 400 BC, and Archimedes' worm wheel dates from about 200 BC. In 40 BC Vitruvius described a grain mill powered by a water wheel and gear transmission, and in 28 BC someone equipped a carriage with an odometer.
Brian Dunning devoted an episode of Skeptoid to the Antikythera Mechanism: http://skeptoid.com/episodes/4184
Also, your initial statement is sine dicendo, therefore useless and rather questions the reason of your comment.
Obviously the Antikythera mechanism is impressive because of the size and detail of the gears and their usage for computation.
The reason for my comment that our ancestors were not as stupid as some contemporary people think, was in reaction on another post which stated that the Antikythera Mechanism was probably just a hundred-year old clock thrown overboard in recent times (I should have quoted that comment for clarity).
Some people cannot fathom that ancient people could realize impressive feats, just like we can. Take for example the pyramids: "the old Egyptians could never have build themselves, they must have gotten extraterrestrial help". This condescending view is also propagated by Von Daniken in his 'Chariots of the Gods' books.
It's a contender in the list of 'biggest pseudo scientific bs', runner up is the scientology junk.
"Romans were the first to invent mass production. They figured out how to use water wheels to create a factory flour mill."