 What are Darwin's finches, and why are they so important to biologists? The study of finches led to the development of one of the most important scientific theories of all time. But how did this come about? In December 1831, a naturalist called Charles Darwin boarded the HMS Beagle bound on a surveying voyage to 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 Galopagos Islands near Ecuador. What Darwin found there surprised him greatly. As well as giant tortoises and marina guanas, Darwin collected and preserved a variety of different songbirds called finches. Upon returning to the UK, he examined them together with hornetologist 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 colonized the island. However, the Galopagos 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 Galopagos. Some of the birds had long thin beaks and sharp claws suited to catching and eating insects, while 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 or 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. In this video, you have learned how the finches of the Galopagos Islands led to the development of the theory of evolution by natural selection. Is evolution of these birds still happening? See what you can find out.