Weapons reduce the distance between the strongest and weakest members of a group, especially projectile weapons, and change what it means to become a powerful and dominant leader within a social group. When weaker individuals can band together in coalitions with the use of weapons to topple a physically dominant alpha, new skills become more valuable than physical dominance alone.
“Once weapons enter the picture,” write Kevin Simler and Robin Hanson in The Elephant in the Brain, “physical strength is no longer the most crucial factor in determining a hominid’s success within a group. It’s still important, mind you, but not singularly important. In particular, political skill – being able to identify, join, and possibly lead the most effective coalition – takes over as the determining factor.”
Political skills are not so important if your species rarely interacts in groups. If you live mostly in isolation, occasionally meet another member of your species to mate or fight over food, being politically skilled is not too important. Hanson and Simler argue that weapons and a change in power dynamics is what set the human brain on a path toward ever greater evolution. Political skill requires mental acuity, deception, the ability to signal loyalty, and the ability to relate and connect with others. The better your brain is at doing the complex work required for these skills, the more likely you will survive long enough to reproduce. This created the environment for our brains to begin to enlarge, since individuals with bigger brains and more intelligence were generally favored over those who were a little less cognitively capable and therefor less politically and socially skilled.
I think it is interesting and important to consider the factors that shaped human evolution. Understanding how our brain came to be the way it is helps us understand why we act the way we do, why we see certain types of biases in thinking, and how we can overcome mistakes in our ways of thought. By acknowledging that our brains developed to be devious, and that our brains did not develop to give us a perfect view of reality, we can better think about how we design institutions and settings to help us think in the most productive ways possible.