The arms race between [predators] and [prey] is asymmetric,....

“ The arms race between [predators] and [prey] is asymmetric, in which success on either side is felt as failure by the other side, but the nature of the success and failure on the two sides is very different. The two sides are 'trying' to do very different things. [Predators] are trying to eat [prey]. [Prey] are not trying to eat [predators], they are trying to avoid being eaten by [predators].From an evolutionary point of view asymmetric arms races are more [likely] to generate highly complex weapons systems. ”

Richard Dawkins

From : The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design