Human brains are not particularly friendly.
I would disagree. The overwhelming majority of the average human's life is spent peacefully. It is actually fairly remarkable how rarely we have significant conflict, especially considering the relatively overcrowded places that humans live. Not to mention that it is only a small proportion of the human population that engages other humans destructively (not by proxy).
I declare this Open Thread open for discussion of Less Wrong topics that have not appeared in recent posts.