Here is another analogy, one that has been used before. Fling your arms wide in an expansive gesture to span all of evolution from its origin at your left fingertip today at your right fingertip. All the way across your midline to well past your right shoulder, life consists of nothing but bacteria. Many-celled, invertebrate life flowers somewhere around your right elbow. The dinosaurs originate in the middle of your right palm, and go extinct around your last finger joint. The whole story of Homo sapiens and our predecessor Homo erectus is contained in the thickness of one nail-clipping. As for recorded history; as for the Sumerians, the Babylonians, the Jewish patriarchs, the dynasties of Pharaohs, the legions of Rome, the Christian Fathers, the Laws of the Medes and Persians which never change; as for Troy and the Greeks, Helen and Achilles and Agamemnon dead;as for Napoleon and Hitler, the Beatles and Bill Clinton, they and everyone that knew them are blown away in the dust from one light stroke of a nail-file.
Richard Dawkins, Unweaving the Rainbow