[HarHarVeryFunny]

Having a mammalian cortex (or avian cortex equivalent) is what give you the ability the predict. The cortex is the prediction machine - capable of overriding our evolutionary-earlier reactionary behavior with planned behavior based on prediction.

The ability to predict is surely what drove development of the cortex, since the benefits are massive - allows you to know what comes next when you hear the roar of a tiger, or see a poisonous snake, or make a plan, rather than waiting until something bad is actually happening to you.

Parts of our cortex specialized to social behavior would have come later. I doubt bullshit generation/detection would have been a specific driver though! As girls attracted to "bad boys" attest, the urge to merge is far more basic than that.