On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection (1858)
by C. Darwin Esq., F.R.S., F.L.S., &c F.G.S., A. Wallace Esq.
"This MS. work was never intended for publication, and therefore was not written with care."
This paper was the first announcement of the groundbreaking theory of natural selection, which created a new generation of thinking in biology. Darwin went on to write his famous On The Origin of Species
after this publication. (Darwin 1858