Charles Darwin was an English naturalist who studied variation in plants, animals and fossils during a five-year voyage around the world in the 19th century. Darwin visited four continents on the ship HMS Beagle.
Darwin observed many organisms including finches, tortoises and mocking birds, during his five week visit to the Galapágos Islands, near Ecuador in the Pacific Ocean. He continued to work and develop his ideas once he returned from his voyages.
Darwin's theory of evolution challenged the idea that God made all the animals and plants that live on Earth, which contradicted the commonly held Christian views of his era. He did not publish his scientific work and ideas until 28 years after his voyage.
Finally, as a result of Darwin's world expedition and observations, which were backed by many years of experimentation; his discussions with like-minded scientists and his developing knowledge of geology and fossils; he proposed the theory of evolution by natural selection.
Darwin proposed that:
This theory is called natural selection.