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 rhea (though their territories overlapped), that mockingbirds collected on the Galápagos Islands represented three separate species each unique to a particular island, and that several distinct birds from those islands were all classified as finches. Darwin began speculating, in a series of notebooks, on the possibility that "one species does change into another" to explain these findings, and around July sketched a genealogical branching of a single evolutionary tree, discarding Lamarck's independent lineages progressing to higher forms. Unconventionally, Darwin asked questions of fancy pigeon and animal breeders as well as established scientists. At the zoo he had his first sight