Sex at Dawn by Ryan and Jethá. To me, they're by far the most fascinating (non-human) ape, so I'm always surprised at how many people have never heard of them. Vanessa Woods' 2010 book Bonobo Handshake has hopefully helped somewhat to remedy that.
If you know anything at all about bonobos, it's probably that they have a lot of sex. Sex with relatives, troupe-mates and strangers of every age and gender, in various positions (including missionary, which researchers once thought only humans were "advanced" enough to employ), and in all sorts of contexts. Sex is used to diffuse tense or exciting situations, to greet others, to ease anxiety, and to express affection. It comes as easy as a handshake, hence the title of the book.
All this sex has produced a remarkably egalitarian society. There are no lack of violent chimp stories, but you simply don't find the same among bonobos. Alliances of females, not alpha males, keep the peace. Woods tells of her unwitting role as a guest and researcher at the world's only bonobo sanctuary in the Congo in the midst of that country's endless string of gruesome wars and the bonobos dwindling population.
She makes frequent contrast between the bonobos and the chimps she had previously worked with, but the more searching and central question probes the human capacity for both aggression and empathy in light of the horrific stories of war she hears from the staff at Lola Ya Bonobo.
When we call someone an animal, we believe they're cruel and unfeeling and acting on baser impulses. But by this definition, humans are certainly more animal than bonobos. It's difficult to read the accounts of genocide, greed, global apathy and mass rape and that pepper Woods' account and not come out deeply ambivalent about human cooperation. One need not even look to a place like the Congo for distressing examples. Just last week, a woman jogging on the trail I frequently bike to work on was knocked unconscious and raped in the woods not two miles from my house.
Knowing the book was going to be about war and traumatized baby bonobo orphans, I hesitated to pick it up at first, but Woods' story is still upbeat and entertaining, especially when she describes the personalities and intriguing relationships of all the bonobos and staff at the sanctuary. Her message is also ultimately a hopeful one: bonobos are the living example that apes like us can live harmoniously.