Charles Darwin is known for his groundbreaking theory on evolution, particularly for his concept of natural selection. Published in his seminal work "On the Origin of Species" in 1859, Darwin proposed that species evolve over time through a process where traits that enhance survival and reproduction become more common in each generation. His observations during the voyage of the HMS Beagle, especially the diverse species of finches on the Galápagos Islands, were instrumental in shaping his ideas. Darwin's theory revolutionized biology and our understanding of life on Earth, influencing numerous scientific fields.