Struggle for Existence - In this, chapter 3, Darwin first uses Natural Selection in capital letters. Shit just got serious! This chapter stresses the checks and balances of nature and how a somewhat biospheric homeostasis exists for life on earth. Darwin gives examples of species and how they can be said to struggle against oppositions in nature that prevent them from pandemic monopoly. Under that same prevention, the natural "preventor" is then similarly prevented from over-success by another opposition in nature, creating a cycle of what seems like multiple participants in a governing body all ensuring no one department becomes too powerful and abuses the resources. Also outlining competition between different species, Darwin briefly notes, individuals within a species and confound to the same area, will be in competition with one another as they share similar needs to the same resources. This reminds me, shoots me fast forward to the world of Richard Dawkins and The Selfish Gene, where Dawkins touches on aggression and evolutionary stable strategies in the chapter titled, Aggression: stability and the selfish machine. He ends the second paragraph thus:
Natural selection favors genes that control their survival machines in such a way that they make the best use of their environment. This includes making the best use of other survival machines, both of the same and of different species.
Included in the struggle for existence are obvious instances in which a species or individuals of species are caused to compete and sometimes even battle for resources. Whether it be inter-special, in the case of Dawkins exampled lion and antelope "competing" for the meat of the antelope's body or between two lions fighting over territory. The chapter in The Selfish Gene introduces Evolutionary Stable Strategies (ESS). Not easily explained in so few words but in a nutshell, "a strategy which, if most members of the population adopt it, cannot be bettered by an alternative strategy." Using ESS models in regards to aggression between same species, we can see that natures eventually produces order in stabilize competition between these individuals. ESS also apply to inter-special competition just under different models--meaning what works between lion and lion will differ between lion and antelope. If all of these aggressive interactions between individuals, regardless of species, living relatively together in the same ecosystem, are regulated by ESS then it follows that natural selection favors individuals who do not deviate from models which ESS have ruled as dominant among species.