The fallibility of the human mind is a source of continual frustration to philosophers, artificial intelligencers and evolutionary psychologists. Our memories are weak, we are credulous and easily led to believe improbable or impossible things, our language is not optimally constructed. We have problems with probabilities, and are logically inconsistent. We make choices that are apparently irrational and not in our own best long-term interests, and certainly not in those of our genes. Thus - according to Marcus - we prefer instant gratification to the chance of greater, longer-term benefits. We get drunk, embark on non-procreative sex for mere pleasure, and may even sacrifice our lives for some perceived cause that has nothing to do with increasing our inclusive (genetic) fitness.