On the Origin of Species by Alfred Russel Wallace, claimed that patterns in the geographical distribution of living and fossil species could be explained if every new species always came into existence near an already existing, closely related species. Charles Lyell recognised the implications of Wallace's paper and its possible connection to Darwin's work, although Darwin did not, and in a letter written on 1–2 May 1856 Lyell urged Darwin to publish his theory to establish priority. Darwin was torn between the desire to set out a full and convincing account and the pressure to quickly produce a short paper. He met Lyell, and in
On the Origin of Species to the past inhabitants of that continent. These facts seemed to me to throw some light on the origin of species—that mystery of mysteries, as it has been called by one of our greatest philosophers. Darwin refers specifically to the distribution of the species rheas, and to that of the Galápagos tortoises and mockingbirds. He mentions his years of work on his theory, and the arrival of Wallace at the same conclusion, which led him to "publish this Abstract" of his incomplete work. He outlines his ideas, and sets out the essence of his theory: As many more individuals of