The book is divided into three sections each of which have three chapters each based on a biological bias.
The biological biases explored are
1. Conformity
2. Religiosity
3. Tribalism
Then each of these biases are explored from 3 angles
1. How they were side effects of evolutionary fitness adaptations
Introducing concepts such as overintimation, wild religion, minimally counterintuitive intuition and mechanisms of non-biological identity fusion.
2. How they were scaled to enable complex societies, organized religion and militaries
Introducing concepts such as ritual routinization, moralizing religions and sacred values.
3. How we (in the author's opinion) can use them for good in a secular world to solve climate change, promote ethical consumerism and end war.
To be honest, I found the author's opinions on these matters painfully naive but YMMV.
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The good parts is that the author references tons of research and his research group has compiled two huge databases over decades, namely
1. Database of rituals collected from ~600 different cultures around the world
2. Database of historical events classified according to various criterias
Using this, the author builds a reasonable cause-effect timelines. If almost all cultures that have X ritual, subsequently exhibit Y behaviour - then we can have a reasonable argument that X caused Y.
Similarly, if the evolution of civilization in multiple of locations have X criteria satisfied, subsequently exhibit Y outcome - then we can have a reasonable argument that X caused Y.
Of course, these are associations and therefore, cannot be 100% conclusive.
Yet, considering we cannot run multiple timelines of history or multiple social cultures with control and independent variables - it is better than pure speculative.
However, we cannot run multiple parallel human cultures or multiple parallel civilizations in a lab tweaking an independent variable keeping all other variables constant.
So, this is better than pure speculation.
Even so, this is still a highly speculative book and one of those book where it is more of read and think flavour rather than a read and learn flavour.
(I guess that's the cause with all evolutionary psychology/biology literature since there is really no way to truly prove a cause-effect in this area, just reasonably speculate)
I would normally rate the book as 4 stars but the last section was pretty weak. I don't think much would be lost if the last section was skipped - the meat is in the first two sections.