Group isolation tends to produce huge variation among guerrilla groups, even within a single theater of operations.
Guerrilla bands (along with the underground cells and auxiliary networks that support them) are under selective pressure from an environment that instantly and lethally punishes maladaptive behavior.
Kinship and social ties among members of different groups, horizontal transfer of members, cross-pollination of ideas, lifeboat effects (where remnants from destroyed groups survive by rallying to other groups, bringing with them new adaptive traits), and connectivity (increased access to cellphones, the internet, secure messaging, and social media) create means of replication whereby beneficial behaviors can be passed from one group to others.
➡️ As it turns out, these three factors—variation, selective pressure, and replication—are the building blocks of the evolutionary process known as “natural selection.”