Charles Darwin is known as the father of evolution. When he was a young man, Darwin set out on a voyage on the HMS Beagle. The ship sailed from England in late December of 1831 with Charles Darwin aboard as the crew's naturalist. The voyage was to take the ship around South America with many stops along the way. It was Darwin's job to study the local flora and fauna, collecting samples and making observations he could take back to Europe with him of such a diverse and tropical location.
The crew made it to South America in a few short months, after a brief stop in the Canary Islands. Darwin spent most of his time on land collecting data. They stayed for more than three years on the continent of South America before venturing on to other locations. The next celebrated stop for the HMS Beagle was the Galapagos Islands off the coast of Ecuador.
Charles Darwin and the rest of the HMS Beagle crew spent only five weeks in the Galapagos Islands, but the research performed there and the species Darwin brought back to England were instrumental in the formation of a core part of the original theory of evolution and Darwin's ideas on natural selection which he published in his first book On the Origin of Species. Darwin studied the geology of the region along with giant tortoises that were indigenous to the area.
Perhaps the best known of Darwin's species he collected while on the Galapagos Islands were what are now called "Darwin's Finches". In reality, these birds are not really part of the finch family and are thought to probably actually be some sort of blackbird or mockingbird. However, Darwin was not very familiar with birds, so he killed and preserved the specimens to take back to England with him where he could collaborate with an ornithologist.
Finches and Evolution
The HMS Beagle continued to sail on to as far away lands as New Zealand before returning to England in 1836. It was back in Europe when he enlisted in the help of John Gould, a celebrated ornithologist in England. Gould was surprised to see the differences in the beaks of the birds and identified the 14 different specimens as actual different species - 12 of which were brand new species. He had not seen these species anywhere else before and concluded they were unique to the Galapagos Islands. The other, similar, birds Darwin had brought back from the South American mainland were much more common, but different than the new Galapagos species.
Charles Darwin did not come up with the Theory of Evolution on this voyage. As a matter of fact, his grandfather Erasmus Darwin had already instilled the idea that species change through time in Charles. However, the Galapagos finches helped Darwin solidify his idea of natural selection. The favorable adaptations of Darwin's Finches' beaks were selected for over generations until they all branched out to make new species.
These birds, although nearly identical in all other ways to mainland finches, had different beaks. Their beaks had adapted to the type of food they ate in order to fill different niches on the Galapagos Islands. Their isolation on the islands over long periods of time made them undergo speciation. Charles Darwin then began to disregard the previous thoughts on evolution put forth by Jean Baptiste Lamarck who claimed species spontaneously generated from nothingness.
Darwin wrote about his travels in the book The Voyage of the Beagle and fully explored the information he gained from the Galapagos Finches in his most famous book On the Origin of Species. It was in that publication that he first discussed how species changed over time, including divergent evolution, or adaptive radiation, of the Galapagos finches.