Carl Sagan, Cosmos

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