Will the friendliest survive?

Some days ago, Stephen Sackur interviewed Rutger Bregman in the BBC program "Hard Talk," about his new book "Humankind: A Hopeful History." I would have liked to rush to buy it online from my favorite local book store, but some weeks ago it disappointed me being totally unable to process an on-line transaction. So I have to confess that I went to Amazon, and in a few seconds I had the book in my Kindle.
The book is a sequence of examples of evidence that in human nature, the friendly cooperative side dominates our violent instincts. It is precisely our cooperative, friendly nature, that has provided our species an evolutionary advantage over some competitors. According to Bregman, the Neanderthals were probably more intelligent, but they were less friendly, and therefore less able to socialize and cooperate, at a moment in time where doing things together was crucial. Some well-known stories that were well established in the history of science as proof that humans are prone to conflict and collapse, are challenged by the author with more recent evidence. For example, it is most probably not true that the Easter Island society collapsed due to an ecological and social conflict endogenously self-inflicted by humans, as explained by the polymath  Jareed Diamond in his book "Collapse." Apparently, Easter Island never had a very large population, so there was not much to collapse from, and probably its ecological crisis was due to natural phenomena. The Robbers Cave experiment, an experiment directed by a social psychologist in the 1950s in the US where summer camp children showed the dangers of tribalism (and that I explain to my students in my course on Soccer and Economics), was probably manipulated by its author. In wars, soldiers in the field show much less aggressive behavior than expected.
Other things mentioned in the book we already knew, like for example that the "tragedy of the Commons" suggested by Hardin is not inevitable, as shown by the field research of Nobel prize winner Elinor Ostrom. Or that intrinsic incentives are very important, and sometimes may be crowded out by extrinsic incentives. These two things I do teach them to my students.
Of course, where Bregman has more difficulties is in explaining why humans, in spite of our friendliness, have incurred in phenomena like ethnic cleansing or the Holocaust. His explaination is that friendliness is more easily shown to our group members. But then he provides no clue about what defines the group, and why if the group extended from the family, to the tribe, and then the nation of strangers, why it cannot be expanded to the whole human group or beyond.
There is no doubt that our cooperative side has been overlooked, and that institutions should be designed to extract the best from humans. That's the main message of the book, although there is little detail on how to do it. And when there is detail, it is unconvincing. For example, the participatory politics of some Venezuelan or Brazilian municipalities, clearly must have had a difficult time scaling up, if we look at the dismal condition of the two countries at the moment. Between our cooperative genes and our selfish genes there is most probably a polycentric equilibrium (several types coexisting), and the difficult but key challenge is to create the conditions for our cooperative side to dominate and become dominant in the overall population of types. The next crucial stage of this battle will be the November presidential election in the US.