Carl Sagan, Cosmos
Sagan's Cosmos, p. 30-1.<br/>
"The first living things were not anything so complex as a one-celled organisms, already a highly sophisticated form of life. The first stirrings were much more humble. In those early days, lightning and ultraviolet light from the Sun were breaking apart the simple hydrogen-rich molecules of the primitive atmosphere, the fragments spontaneously recombining into more and more complex molecules. The products of this early chemistry were dissolved in the oceans, forming a kind organic soup of gradually increasing complexity, until, one day, quite by accident, a molecule arose that was able to make crude copies of itself, using as building blocks other molecules in the soup."