Ever-escalating demands on cognition...........

      "The worst problems for people," says primatologist Dario Maestripieri, "almost always comes from other people."

      The earliest Homo Sapiens lived in small tight-knit bands of 20 to 30 individuals.  These bands were our "groves" or "forests" in which we competed not for sunlight, but for resources more befitting a primate:  food, sex, territory, social status.  And we had to earn these things, in part, by outwitting and outshining our rivals.

     This is what's known in the literature as the social brain hypothesis, or sometimes the Machiavellian intelligence hypothesis.  It's the idea that our ancestors got smart primarily in order to compete against each other in a variety of social and political scenarios.

     "The way the brains of human beings have gotten bigger at an accelerating pace," writes Matt Ridley in his book on evolutionary biology, The Red Queen, "implies that some such within-species arms race is at work."  Steven Pinker and Paul Bloom also emphasize intra-species competition as an evolutionary cause of our intelligence.  In an influential 1990 article on language evolution, they write, "Interacting with an organism of approximately equal mental abilities whose motives are at times outright malevolent makes formidable and ever-escalating demands on cognition."

      Robert Trivers goes even further.  He argues that it was the arms race between lying and lie detection that gave rise to our intelligence.  "Both the detection of deception and often its propagation have been major forces favoring the evolution of intelligence.  It is perhaps ironic that dishonesty has often been the file against which intellectual tools for truth have been sharpened."

-Kevin Simler and Robin Hanson, The Elephant In The Brain