In the second half of the 20th century, classic research by Princeton University’s Peter and Rosemary Grant provided evidence of quite strong natural selection on beak size and shape. By the mid-20th century, there was abundant evidence that Galapagos finches had evolved to fill the range of ecological niches available in the archipelago – a classic example of evolution by adaptive radiation.īeak size and shape were key attributes in determining adaptation to the different types of food available. Increasingly, other biologists were drawn into resolving the questions about finches that Darwin had left unanswered.īy the end of the 19th century, Galapagos finches were among the most studied of all birds. Why, then, do people now label them as “Darwin’s finches”, and why are these finches now regarded as a classical textbook example of his theory of evolution by natural selection? Paragons of evolutionĭespite not mentioning Galapagos finches, Darwin did make much use of evidence from other Galapagos species (especially mockingbirds) in Origin of Species.Īs the influence of Origin of Species spread, so too did the evolutionary fame of the Galapagos Islands. Presumably, it was his doubt about the available evidence that resulted in Darwin making no mention of Galapagos finches in any edition of Origin of Species.

This was partly because the specimens available to him were not sufficiently labelled as to their island of collection. Unfortunately for Darwin, the closer he examined the available evidence on Galapagos finches, the more confusing the picture became. The famously varied beak shapes of the Galapagos finches, as illustrated in the second edition of Darwin’s Journal of Researches.

So intrigued was Darwin by this variation in size and shape of beaks that in the second (1845) edition of Journal of Researches he included illustrations of the distinctive variation between species in the size and shape of their beaks. As painstakingly shown by Frank Sulloway and more recently by John Van Whye, it wasn’t until two years later that the finches sparked Darwin’s interest.īy then he had received feedback from the leading taxonomist of the time, John Gould, that the samples comprised 14 distinct species, none of which had been previously described! Gould also noted that their “principal peculiarity consisted in the bill presenting several distinct modifications of form”. When Charles Darwin visited the Galapagos Islands in October 1835, he and his ship-mates on board HMS Beagle collected specimens of birds, including finches and mockingbirds, from various islands of the archipelago.Īt the time, Darwin took little interest in the quaint finches, making only a one-word mention of them in his diary.

Radiation island unity