The study of finches led to the development of one of the most important scientific theories of all time.

In December 1831 a naturalist called Charles Darwin boarded the HMS Beagle, bound on a surveying voyage of South America. Whilst the ship and crew carried out coastline surveys, Darwin was free to explore the islands en route. In 1835 the Beagle arrived at the Galapagos islands, near Ecuador. What Darwin found there surprised him greatly. As well as giant tortoises and marine iguanas, Darwin collected and preserved a variety of different songbirds called finches. Upon returning to the UK he examined them together with ornithologist John Gould, and made some fascinating discoveries.

The scientists observed that the birds were all similar to a single type of finch found on mainland South America, suggesting that these mainland finches had originally colonised the islands. However the Galapagos finches were all slightly different from the original mainland species, and they were also different from each other. The finches on each island showed distinct variations in their overall size, beak shape and claw size. These differences were attributed to the differing food sources available on the various islands of the Galapagos. Some of the birds had long thin beaks, and sharp claws suited to catching and eating insects, whilst others had large powerful beaks suitable for cracking open nuts. Because of the distances between the islands, breeding between different species of finch was unlikely, and Darwin concluded that the finches must have evolved over time from the original mainland species to suit the conditions found on each individual island. In all, 13 of the birds brought back by Darwin were identified as being entirely new species, all similar to each other, but with definite variations from their common ancestor. Darwin proposed that the variations seen both within and between the finch species arose by chance.

Variations which gave any individual a competitive advantage made them more likely to survive and therefore reproduce, out-competing those with less advantageous characteristics. Darwin called this theory Natural Selection and he published it in his book “On the Origin of Species” in 1859. Evolution by natural selection is now widely agreed to be the most accurate theory to explain the origin and diversity of all life on Earth.

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Credits:
- FuseSchool - Global Education, 2017. Evolution by Natural Selection - Darwin's Finches | Evolution | Biology | FuseSchool.
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