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Darwin's Finches Evolve Before Scientists' Eyes
By Sara Goudarzi
LiveScience Staff Writer
posted: 13 July 2006
02:00 pm ET


For the first time scientists have observed in real-time evolutionary changes in one species driven by competition for resources from another.

In a mere two decades, one of Charles Darwin's finch species, Geospiza fortis, reduced its beak size to better equip itself to consume small sized seeds, scientists report in the July 14 issue of the journal Science.

The finch once had its own kingdom on the Galapagos Island of Daphne Major. It had its pick of seeds to eat. But the arrival of another species of finch about 20 years ago, and additional food competition from a drought on the island in 2003, changed everything.

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During the 1977 drought on the Galapagos islands, the
beak size of the finch Geospiza fortis increased by 4%.
Finches with larger beaks are able to feed on larger
seeds, and these were more abundant than smaller ones
during the drought.

Courtesy of Peter Grant.

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Originally posted by pleco

I eagerly await AiG's scientific analysis of this observation.

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The passage in chapter 17 in the Voyage of the Beagle in which Darwin describes the finches and surmises that they may have shared a common ancestor is shown below:

The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body and plumage: there are thirteen species, which Mr. Gould has divided into four subgroups. All these species are peculiar to this archipelago; and so is the whole group, with the exception of one species of the sub-group Cactornis, lately brought from Bow Island, in the Low Archipelago. Of Cactornis, the two species may be often seen climbing about the flowers of the great cactus- trees; but all the other species of this group of finches, mingled together in flocks, feed on the dry and sterile ground of the lower districts. The males of all, or certainly of the greater number, are jet black; and the females (with perhaps one or two exceptions) are brown. The most curious fact is the perfect gradation in the size of the beaks in the different species of Geospiza, from one as large as that of a hawfinch to that of a chaffinch, and (if Mr. Gould is right in including his sub-group, Certhidea, in the main group) even to that of a warbler. The largest beak in the genus Geospiza is shown in Fig. 1, and the smallest in Fig. 3; but instead of there being only one intermediate species, with a beak of the size shown in Fig. 2, there are no less than six species with insensibly graduated beaks. The beak of the sub-group Certhidea, is shown in Fig. 4. The beak of Cactornis is somewhat like that of a starling, and that of the fourth subgroup, Camarhynchus, is slightly parrot-shaped. 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. In a like manner it might be fancied that a bird originally a buzzard, had been induced here to undertake the office of the carrion-feeding Polybori of the American continent.

"Mr. Gould" (above) refers to John Gould, the famous English ornithologist.

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