According to Henry Nicholls in The Galápagos: A Natural History, part of Charles Darwin's inspiration for his Theory of Evolution came out of bad accounting.
Back in the 1800's, standard operating procedure for a naturalist was to capture and kill any number of small creatures. Pack 'em in salt, pickle 'em, pile 'em into boxes to ship home. All in the interest of scientific study.
So young Darwin, circling the globe as the resident naturalist aboard The Beagle, harvested hundreds of animal specimens and squirreled away crate after crate of fossils and plants.
But there were so many. As it happened, he neglected to properly label some carcasses from the Galapagos.
No doubt he'd never expected there to be much difference between, say, a dark little finch from Floreana and that other one from nearby Isabela.
Poor guy: back home in chilly England, unpacking box after box of corpses and he discovered the awful truth: his sparrows weren't labeled very well.
Or maybe not.
In any case, Galápagos mockingbirds are also distinctively different from mockingbirds on the mainland. And they are different from one Galápagos island to another.
Which leads, step by painful step, to Darwin's theory of evolution and the eventual publication in 1859 of On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Phew.
Sidebar drama: Interestingly enough, as a Christian, Darwin was troubled by the implications of what he discovered. However, when a naturalist pal of his, Alfred Wallace, came up with a parallel theory, Darwin's misgivings subsided enough for Darwin to polish up his own manuscript and send it to a publisher. It became an overnight sensation.
While we were doing our own exploration in the Galápagos (zero collection of specimens, thousands of photos, great guides, and a tidy ship thanks to AdventureLife), we stumbled across a little mockingbird family drama on Floreana.
Or maybe it's a daily show staged to entrance the tourists –– 14:00-15:20 beached walrus pups, 15:20-15:40 mockingbird display, 15:40-whenever tortoise crossing.