During
the survey voyage of
HMS Beagle, Darwin was unaware of the significance of the birds of the Galápagos. He had learned how to preserve bird specimens from
John Edmonstone while at the
University of Edinburgh and had been keen on shooting, but he had no expertise in
ornithology and by this stage of the voyage concentrated mainly on geology. In Galápagos he mostly left bird shooting to his servant
Syms Covington. Nonetheless, these birds were to play an important part in the
inception of Darwin's theory of
evolution by
natural selection. On the
Galápagos Islands and afterward, Darwin thought in terms of "centres of creation" and rejected ideas concerning the
transmutation of species. From
Henslow's teaching, he was interested in the geographical distribution of species, particularly links between species on oceanic islands and on nearby continents. On
Chatham Island, he recorded that a
mockingbird was similar to those he had seen in
Chile, and after finding a different one on
Charles Island he carefully noted where mockingbirds had been caught. Following his return from the voyage Darwin presented the finches to the
Zoological Society of London on 4 January 1837, along with other mammal and bird specimens that he had collected. The bird specimens, including the finches, were given to
John Gould, the famous English
ornithologist, for identification. Gould set aside his paying work and at the next meeting, on 10 January, reported that the birds from the Galápagos Islands that Darwin had thought were
blackbirds, "
gross-beaks" and
finches were actually "a series of ground Finches which are so peculiar [as to form] an entirely new group, containing 12 species." This story made the newspapers. Darwin had been in
Cambridge at that time. In early March, he met Gould again and for the first time to get a full report on the findings, including the point that his Galápagos "
wren" was another closely allied species of finch. The
mockingbirds that Darwin had labelled by island were separate species rather than just varieties. Gould found more species than Darwin had expected, and concluded that 25 of the 26 land birds were new and distinct forms, found nowhere else in the world but closely allied to those found on the
South American continent. From these, Darwin tried to reconstruct the locations from where he had collected his own specimens. The conclusions supported his idea of the transmutation of species. In the first edition of
The Voyage of the Beagle, Darwin said that:It is very remarkable that a nearly perfect gradation of structure in this one group can be traced in the form of the beak, from one exceeding in dimensions that of the largest gros-beak, to another differing but little from that of a warbler. By the time the first edition was published, the
development of Darwin's theory of
natural selection was in progress. For the 1845 second edition of
The Voyage (now titled
Journal of Researches), Darwin added more detail about the beaks of the birds, and two closing sentences which reflected his changed ideas:Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.
Text from On the Origin of Species Darwin discussed the divergence of various species of birds in the Galápagos more explicitly in his chapter on geographical distribution in
On the Origin of Species; however, he does not single out the finches: == Polymorphism in Darwin's finches ==