Charles Robert Darwin was a British naturalist. In 1831, he got a job on the H.M.S. Beagle (an exploration ship). The ship sailed to South America to map the continent's coastline. The Beagle voyage took five years to complete. While Darwin was on the voyage, the crew found a group of islands off the coast of Ecuador, South America. Today these islands are known as the Galapagos Islands.

     The Galapagos Island studies proved to be Darwin's most famous work. He studied hundreds of species of plants and animals on the islands. One animal he was especially interested in was the mockingbirds. Darwin wondered why the mockingbirds found on different islands had different shaped beaks. Eventually he realized the differences were because the bird's food varied on each island. He also discovered that the characteristics of finches and tortoises differed from island to island. He believed similar species must have evolved, or changed, from a common ancestor and these changes would have to take generations to happen.

     Darwin believed animals struggled for resources such as food and land. The animals that had advanced traits lived longer. Longer life meant the animals would mature and reproduce which would in turn pass the advanced traits on to their offspring. The animals with the weaker traits would not live long enough to reproduce. This is called natural selection. Tiny changes over hundreds of years would lead to variations in the animals. 

     In 1859, Darwin wrote a book titled "The Origin of Species by Means of Natural Selection". He knew the book would not be popular, so he did not publish it because it conflicted with many people's religious beliefs.

    Many myths and unanswered questions have come from Darwin's findings. However, Darwin NEVER said that humans came from monkeys like many people believe. He stated that humans and monkeys may have had a common ancestor.