Order, disorder, cruelty
Cruelty is invented by the weak to fend off the strong [analogous to poison], among closely related members of a particular population. The long-term benefit is the creation of barriers that lead to speciation. This is reflected in civil wars, such as that in Greece between 1944 and 1949 , or more recently in the Balkans. In biological terms, it prevents pan-mixing, leading to the formation of recombinants of different types, which, although closely related to their origins, can easily differentiate themselves, creating sub-populations. In terms of cultures, this is creates groups that invent a history that they do not want to share with others, thus creating effective barriers to intercultural marriages. The closer the groups are, the more cruel they have to be to separate from each other.
The text of the presentation Order, Disorder, Cruelty is in French, and the slides of the presentation are in English.