|Six of the 15 varieties of pigeons Darwin bred from a single original family.|
In fact, he wasn't even particularly interested in finches. While sailing the Galapagos, he and several members of the crew gathered and stuffed dozens of them, then simply dumped them indiscriminately into bags, leaving the job of cataloging them to more serious naturalists.
The 22-year-old Darwin didn't even consider himself a scientist, bent on changing the world. He was, at the time, determined to become a priest for a quiet Kent church.
Aboard the Beagle, Darwin was an unpaid companion there to keep Captain Robert Fitzroy company, as Fitzroy's predecessor, Captain Pringle Stokes, had blown his brains out to escape the stresses involved in interminable sea voyages.
It wasn't until two decades later, when working with pigeons, that Darwin finally came to his conclusions about the forces which shape evolution. Using the simple process of selection practiced by breeders since prehistory, Darwin created an extremely diverse lineage of fifteen different pigeon breeds - pouters, fantails, tumblers, trumpeters, carriers and more.
Darwin was using the same technique humans have used since prehistory to breed dogs as diverse as the chihuahua, samoid, whippet, poodle, and St. Bernard. All, of course are derived from common stock - originally, the descendants of wolves; and they have diversified to such extremes in the space of just a few short generations.
By Darwin's time, breeders had been using simple selection - choosing plants or animals with preferred traits - the largest, most even-tempered, etc., and breeding them together to derive creatures with the characteristics they sought.
But breeders at the time shared a common complaint - all too often, nature would produce unwanted surprises - traits which nature - not the breeder - had selected; thus the term "natural selection" was first coined by professional breeders, who noticed how natural, unplanned and random processes led to changes among offspring.
When those changes were significant enough to create a creature that could no longer breed among its own lineage, the line of differentiation known as speciation had been crossed.
Source: "The Beak of the Finch", Johnathan Weiner, 1994