Even before that, in his more famous work, Origin of Species (1859), he propounded his theory of natural selection: that the fittest beings survive in nature and successfully propagate their species.
(he; propounded; his theory of natural selection; T:Even before that; L:in his more famous work) (the fittest beings; survive; L:in nature) (the fittest beings; successfully propagate; their species)
he the fittest beings the fittest beings
propounded survive successfully propagate
his theory of natural selection T:Even before that L:in his more famous work
L:in nature
their species