The greatest of Darwin's contributions was to discover the mechanisms leading to that evolution during long periods of time, mechanisms that he centered in natural selection.
(The greatest of Darwin's contributions; was; to discover the mechanisms leading to that evolution during long periods of time) (the mechanisms; leading; to that evolution) (mechanisms; centered; in natural selection)
The greatest of Darwin's contributions the mechanisms mechanisms
was leading centered
to discover the mechanisms leading to that evolution during long periods of time
to that evolution
in natural selection