Many people have the experience (possibly illusory) of being able
to think more clearly, and particularly of being better able to
detect flaws in ideas, when they are in an argumentative frame of
mind. Argument also represents an opportunity to invite other
people to find flaws in one's ideas. Possibly argument is the chief
means by which ideas are improved.
Perhaps not everyone experiences the "benefits" hypothesized above,
but if a significant fraction of the population did so, then the
idea of there being some selection pressure in favor of pure
argumentativeness doesn't seem completely implausible to me.
Particularly if that population were in a clade and had
frequent opportunities to argue with one another and exchange
new ideas arising in argument.
(Then again, maybe I'm just flattering myself. ;)
-- Eric Watt Forste ++ arkuat@pigdog.org ++ expectation foils perception -pcd