Darwin arrived for the first time in Ecuador when he was 26 years old. He got astonished by the great quantity of turtles and iguanas that live in this area, to which he referred as "the paradise for the reptiles." In the scientific expedition on board the Beagle, Darwin traveled in five weeks most of the main islands of Galapagos (San Cristóbal, Floreana, Isabel and Santiago).

In the archipelago he found plants and animals of the same type. Even fossils of extinct animals similar to the modern ones. This way, the naturalist supposed that the marine iguanas came from the terrestrial species of reptiles that extinguished hundred of millions of years ago.

There are 13 species of chaffinches (terrestrial birds) known as they were studied by Darwin. The naturalist sustained that these birds evolved starting from a unique group, for what concluded that the changes were gradual and that millions of years passed, before they adapt to the environment and before they transmit the new characteristics to the following generations.

He explained that the mechanism of the evolution was a process called natural selection and that most of species come from one unique branch. As a result of his investigations, he published the book "The Origin of the Species", in 1859.