If fossil animals have thus given rise everywhere to legends of giants, fossil shells have played the same part as regards legends of a deluge. These are in many cases so abundant at high levels that they could not fail to be observed, and, if observed, to be attributed to the sea having once covered these levels, and inundated all the earth except the highest peaks. The tradition of an universal deluge is however so important that I reserve it for separate consideration at the end of the present chapter. If then all memory of a period so comparatively recent as that of the neolithic stone age and of the latest extinct animals was completely lost when the first dawn of history commences, it follows as a matter of course that nothing like an historical tradition survives anywhere of the immensely longer palæolithic period and of the origin of man. Man in all ages has asked himself how he came here, and has indulged in speculations as to his origin. These speculations have taken a form corresponding very much to the stage of culture and civilization to which he had attained. They are of almost infinite variety, but may be classed generally under three heads. Those nations which had attained a sufficient degree of culture to personify first causes and the phenomena of Nature as gods, attribute the creation of the world and of man to some one or more of these gods; and as they advance further in philosophical reasonings, embellish the myth with allegories embodying the problems of human existence. Thus if Bel makes man out of clay, and moulds him with his own blood; or Jehovah fashions him from dust, and breathes into his nostrils the breath of life; in each case it is an obvious allegory to explain the fact that man has a dual nature, animal and spiritual. So the myth of the Garden of Eden, the Temptation by the Serpent, the Trees of Knowledge and of Life, and the Fall of Adam, which we see represented on a Babylonian cylinder as well as in the second chapter of Genesis, is obviously an allegorical attempt to explain what remains to this day the perplexing problem of the origin of evil. These philosophical myths are, however, very various among different nations. Thus the orthodox belief of 200,000,000 of Hindoos is that mankind were created in castes, the Brahmins by an emanation from Brahma's head, the warriors from his chest, the traders and artisans from his legs, and the sudras or lowest caste from his feet; obviously an _ex post facto_ myth to account for the institution of castes, and to stamp it with divine authority.