Darwin developed his theory of "natural selection" from 1838 onwards and was writing up his "big book" on the subject when Alfred Russel Wallace sent him a version of virtually the same theory in 1858.
Darwin udviklede sin teori om "naturlig selektion" i 1838 og var fremefter i gang med at skrive sin "store bog" om emnet, da Alfred Russel Wallace sendte ham en lignende teori i 1858.