Finch Evolution in the Act

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"Evolution caught in the act" is the headline of an article in news@nature, 13 July 2006. A study of two species of Darwin's finches on one of the smaller Galapagos Islands has "provided the best description of a characteristic trait evolving in the wild." The study was reported in Science vol. 313, p224, 14 July 2006 by Princeton University biologists Peter and Rosemary Grant. They have studied the medium ground finch and the large ground finch on the island of Daphne Major. Both these finches eat seeds but the large ground finches find it easier to eat the large seeds of a low shrub named Tribulus cistoides (Tc) and they have thrived on the island since they first arrived in 1982. The medium ground finch can eat these large seeds but finds it easier to eat small seeds. In 2003 and 2004 there was a drought, and the supply of large Tc seeds was drastically reduced. The smaller birds could more easily eat small seeds, so they survived. In 2004 and 2005 the researchers noted the average size of medium ground finch beaks was smaller than before, and the birds were only eating the large seeds half as often as before.

Editorial Comment: Note well! No birds have actually evolved. They already had beaks of varying sizes and all that has happened is that some birds were already better equipped to cope with drought induced change in seed availability. The ones that weren't, i.e. those with big beaks, died out, while the small beaked birds survived. This is "survival of the fittest" or natural selection, but it is not evolution. The change in average beak size is the result of the larger beaked birds being removed from the statistics in the next generation. This is an ecological change, not an evolutionary one, But it shows how researchers call any change evolution-even when it isn't! (Ref. variation, ecology, elimination)

Evidence News 9th August 2006

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