Charles Darwin was a the man who studied evolution. One theory he came up with was the survival of the fittest. Which means that only the strong specie will survive and the weak ones will die off. Along with adaptation to natural environments, he wrote a famous book about this called "Origins of the Species" in 1859.
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Charles Darwin's book that caused the most controversy was "The Origin of the Species". He had worked on the theory of natural selection for many years, but the book was released in 1859.
24 November 1859On The Origin Of Species By Means Of Natural Selection Or The Preservation Of Favored Races In The Struggle For LifeRaces means species.