Our species has been so successful in spreading over the world, inhabiting every suitable niche and changing the natural environment more to our liking, that it has become difficult to see ourselves "in nature"—to envision ourselves in relation to other forms of life. We humans have set ourselves so far apart from the rest of the natural world that it requires an effort of the imagination to reconstruct our relationship to other life on the planet. Examining what is known of our origins enables us to see ourselves and those relationships more clearly.
How we discovered our own origins is a fascinating story in itself. It was a slow process with many landmark insights along the way and some wrong turns. Because of the theological stakes involved, serious inquiry was not possible as long as church and state power were conjoined in Europe. In 1619, Lucilio Vanini was burned at the stake in Toulouse, France for suggesting that humans might be descended from apes. The process of discovery began in earnest in the eighteenth century when European universities, especially the University of Paris, began to sort through the newly discovered forms of life from around the world and to classify them in related families. Once the great task of classifying the world's life forms got well under way, the affinities between humans and the great apes became obvious. Indeed, the similarities had been noted by the ancient Greeks as well as by the unfortunate Vanini. But by the 18th century knowledge had increased to the point that the similarities could be examined — and in an increasingly systematic way — in the parts of Europe free from the coercive power of the church.
What was lacking in these early speculations about human ties to other forms of life was a comprehensive scientific theory that would explain these family resemblances and provide an account of the changes in our own and other life forms visible in the fossil record.