The famous scientist known for his theory of evolution is Charles Darwin. His groundbreaking work, particularly in "On the Origin of Species," introduced the idea of natural selection as the mechanism for evolution. Darwin's theory challenged existing beliefs about the nature of species and their development, positing that species adapt to their environments over time through a process of survival of the fittest. His scientific observations during the voyage of the HMS Beagle set forth concepts that have fundamentally changed the understanding of biological diversity and the interconnectedness of life on Earth.