Forming a Theory

Darwin realized that being isolated on the islands resulted in special adaptations. These changes happened slowly. Then, over time, new species were formed.

Darwin wasn’t the only scientist to think about evolution. His great contribution was that he could explain how and why evolution occurred. In 1859, Darwin published a book, On the Origin of Species.In it, he proposed that species evolve, or change over time.

Española cactus finch

large ground finch

Darwin also suggested a way in which living things evolve. Natural selection says that some plants and animals have traits that work best in a particular place. These living things are the ones that will survive and reproduce.

Darwin’s thinking helped to change how people saw the natural world. He will always be remembered.