Killing Evolves Intelligence

Killing is essential to the evolution of intelligence. Prey need to become smarter to evade predators, and predators thereby must become even smarter than the prey that are trying to evade them. If there are no predators trying to kill you, you will have no reason to increase your intelligence. Likewise, if you are not hunting for difficult-to-catch prey, you won't develop intelligence either.

If you can easily shoot fish in a barrel, you can be quite dumb and survive. It is the ratcheting feedback loop between predator and prey that exponentially increases intelligence through the course of evolution. Only the smart survive.

A planet of plants and herbivores living in harmony would have no intelligent life because neither would need intelligence to survive. When survival is simple, life is simple. But if survival is challenging, life becomes complex. When multiple species are in constant competition, ever-increasing intelligence is required on both sides of the predator/prey equation.

If intelligence continues to evolve further, however; a species can eventually develop ethics and the freedom of will to elect not to kill other lifeforms even though they could. Life can find a more harmonic way to survive, not out of necessity but choice.