This year, we celebrate two hundred years since the birth of Charles Darwin (1809–1882), one of the world's most creative and influential thinkers, and one hundred and fifty years since the publication of his 1859 book On the Origin of Species. Charles Darwin presented compelling evidence that all living species have evolved over millions of years from a few ancestors through the process he termed natural selection. In 1831, Darwin set out on a British scientific expedition around the world. In South America Darwin found fossils of extinct animals that were similar to modern living species. On the Gala­pagos Islands in the Pacific Ocean he noticed many variations among plants and animals of the same general type as those in South America. Darwin visited many places around the world collecting specimens to further his studies.