Strongly recommend:

The Better Angels of Our Nature: Why Violence Has Declined Steven Pinker

You've likely heard of this; if you haven't you absolutely must at least watch bis TED talk or find an article summary. I'll add my high recommendation.

Weakly recommend:

The ancestor's tale Richard Dawkins

I got what I wanted from this, which was better knowledge of the phylogenetic tree. Still, it wanders around quite a lot, and it makes it seem like he doesn't really understand the probability models being used for the sequence-based evidence that's challenging a lot of the old assumptions.

Micro-motives and macro-behaviour Thomas Schelling

I really only bought this because The Art of Strategy wasn't in the Kindle store. It's an okay set of game theory/group dynamics teasers to sharpen your intuition, but far from essential.