I was thinking of debate, more as a persuasive technique than as a way of discovering the truth. Changing my mind is easy -- the powers of advertising, manipulation, coercion, etc., are all highly refined arts. Arriving at the truth is harder, even if "truth" is merely a plausible choice of one alternative over another.

It seems possible that if stubbornness is a acquired trait, it is one because it confers a survival advantage.