Charles Darwin was probably the 19th century's greatest scientist, best known for his theory of evolution. He was not much good at school but his great moment came when he was invited to join a five-year expedition on a ship called HMS Beagle (1831-36). He was a lousy sailor - always seasick - but a wonderful observer. During his five years, he visited many parts of South America and the Galapagos Islands. (Some of my penguin cousins live there.) Years later, after careful thought and preparation, he wrote a great book called On the Origin of Species (1859), explaining how life had evolved by natural and sexual selection. No-one knew about genes then so he didn't know how this actually happened. But the evidence he brought together in his books and papers was so overwhelming that biological (life) science was changed for ever. It was Darwin who showed once and for all that humans were just another kind of animal, descended from ape-like ancestors, and not some special and unique form of life superior to everything else. This is why he is one of my heroes: he put people in their place and humbled them a bit!