How else would it happen if they didn't do it themselves?

"Wrangham favors the idea that as early people formed cooperative societies, evolutionary pressures favored mates whose features were less “alpha,” or aggressive. “There was active selection, for the very first time, against the bullies and the genes that favored their aggression,” he adds. But so far, “Humans are the only species that have managed this.”

Hmmm. Well. Let's just discount facial features for a minute or two.

Remember that (in evolutionary time) our species only split fairly recently from chimpanzees/bonobos. These are our ''cousins'' and our bodies would accept a blood donation from either of them...that's how close we are. Chimpanzees are male-led and the males are always seeking power/influence among their groups. It's a constant struggle and leads to a very violent society. Bonobos are female-led, begin and end each social encounter with some kind of sexual activity. (Which is why so few zoos exhibit them--they're always doing something which embarrasses parents!)

So, I'll take issue with his idea that we've ''managed'' this. All you need to do is look at a photo of the pustule potus when he's unhappy and you'll see a chimp face! We may use different tools, exchanging political power for rocks and clubs...but most of us are still as aggressive as ever. Wars are much more common than eras of peace. Think of US history and how even our national anthem glorifies a battle. Think of 9-11, concentration camps and other genocides. Chimpish roots remain deep within us. Neanderthals carried them, too, but of course, so do we. And..
anthropologists have concluded that they were probably no more violent or brutal than any other early hominids.

(Interestingly, once you begin to think seriously in evolutionary terms, it's possible to see bonobo traits in many of us. I'd favor a plan to incorporate those genes in humanity and reduce the number of chimpish traits!)