Earlier quoted context omitted.
It's based on the fact that one explanation of why there's not even millions more species of all life, is because the more successful ones simply cannibalized the less successful ones. This would've started even before complex life, almost at the chemical level. I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later, so it came down to eat or be eaten. Sti…
>I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later, Two convergent intuitions as to why this is true, but for the wrong reasons: Species (maybe only [di?]morphic ones) rarely kill other instances of their own species, only maim - usually to the point of socially/reproductive shame/selective behavior; as infra-species violence is usually done for sexua…
Anyway, an interesting point about evolution is that things had to have been eating other smaller things long before the brain had enough processing power for "Species Recognition". It would've initially been a simple brain and rod/cone eye neuron and motor neuron in a fish that executed primary the rule of "See movement then execute tail wag, open mouth, close mouth" in that order. It takes like 5 neurons wired in a specific way to accomplish that. The first neurons had to have been that simple. Indeed the chain reaction of "input photon and convert energy into motor neuron charge potential" had to have been the actual chemical process that eventually developed the first neuron to begin with.
It was only after MUCH more evolution that avoidance of eating one's own species would've been possible by visual inspection of the prey. However, it's true it could have been a 'taste' signal where the scales of your own species had a bad enough taste that you spit it out rather than eating it, and that can be accomplished also with a brain of only a few neurons.