Charles Darwin is regarded as one of the most influential scientists in the history of biology. Born in 1809 in England, he developed a strong curiosity for the natural world from an early age. His most important scientific journey began when he sailed on the ship HMS Beagle, during which he observed a wide variety of plants, animals, fossils, and geographical features. These observations led him to think deeply about how species change over long periods of time. Darwin’s greatest contribution is the theory of evolution by natural selection. According to this theory, individuals in a species show natural variations. Some of these variations help them survive better in their environment. Those individuals who survive are more likely to reproduce and pass their useful traits to the next generation.