Being a social animal is the opposite of being a rational animal. They exist in direct conflict.
Being rational doesn't necessarily preclude social cooperation, but being a social animal absolutely precludes rational behaviour.
Being rational is the dominant strategy, but Earth is a paradise. The environment is way too easy, so Man became ecologically dominant with a strictly inferior strategy, thus releasing most selection pressure on the species.
The Heavens fucked up. They were too merciful. By a lot.
P.S. Earth is a paradise. In Reality, Adam was never kicked out of Eden. You're still there; look up. See a sunset for once in your life. If you think life is hard, it's because you're too stupid not to shoot yourself in the foot. Your problems are all self-inflicted.