Charles Darwin transformed our understanding of the world with the idea of natural selection, challenging the notion that species are fixed and unchanging. These writings from On the Origin of Species explain how different life forms appear all over the globe, evolve over millions of years, become extinct and are supplanted. Great Ideas - Throughout history, some books have changed the world. They have transformed the way we see ourselves - and each other. They have inspired debate, dissent, war and revolution. They have enlightened, outraged, provoked and comforted. They have enriched lives - and destroyed them. Now Penguin brings you the works of the great thinkers, pioneers, radicals and visionaries whose ideas shook civilization and helped make us who we are.