Charles Darwin published his book "The Origin of the Species" in 1859.
I did not enjoy reading Darwin's work. The main things what he says are:.
1. There is limited supply of food and all species struggle for survival.
2. Sometimes there are mutations.
3. Some variations are more useful than others.
4. Species tend to pass on these variations to their offspring.
The first point Darwin makes that all species struggle for existence. Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life. If it is does not happen this way the number of species would quickly become so unordinary great that "no country would support the product." as more individuals are produced than possibly can survive, there must in every be a struggle for existence, either one individual with another of the same species, or with the individuals of distinct species, or with physical conditions of life. Darwin says; if there were not struggle for existence, our earth would be covered by the same progeny of a single pair. According to Darwin " in a state on nature almost every full-grown plant annually produces seeds and amongst the animals there are a very few which do not annually pair. In every plant and animal survive " it would rapidly stock every station in which they could anyhow exist.
The Nature does its share, not every seed, and every egg or animal's off- spring survive. Only those animals and plants survive which are most adapted to the conditions and have some useful variations. If useful variations do ever occur to any organic being, these individuals will have the best chance of being preserved in the struggle for life. Possibly, those species will tend to produce offspring with the same or similar characteristics. This principal of preservation or survival of the fittest is called Natural Selection. I agree with natural selection, because the evolution shows that Darwin's theory it true.