1996 Checkmate on 10-Feb.

From WIRED This Day in Tech: The first chess game between a human champion an a computer took place, with international Grandmaster Garry Kasparov losing to IBM's Deep Blue in Philadelphia. 

We think that this was the first time when the symbol system human (the symbol system hypothesis states that intelligence operates on a system of symbols) lost to a kind of a brute force algorithm.

Wired: Aside from their stunt value, these man-vs.-computer matches have changed the way that chess is played, and not necessarily for the better. “We don’t work at chess anymore,” complained grandmaster Evgeny Bareev. “We just look at the stupid computer, we follow the latest games and find small improvements. We have lost depth.” 

This reminds me on Marshall Mc Luhan: First We Build The Tools  - Then They Build Us, he said.
Not bad, I say. Remove our irrational fear of the "unnatural".