All things, including the species to which we belong, have evolved over vast stretches of time. The evolution is random, though in the case of living organisms it involves a principle of natural selection. That is, species that are suited to survive and reproduce successfully endure at least for a time; those which are no so well suited die off quickly. Other species and vanished existed before we came onto the scene; our kind, too, will vanish one day. Nothing -- from our own species to the sun -- lasts forever. Only the atoms are immortal.-- from an essay on Lucretius by Stephen Greenblatt. But, notes Greenblatt, there is something disturbingly cold in Lucretius' account of pleasure.
In a universe so constituted, Lucretius argued, it is absurd to think that the earth and its inhabitants occupy a central place, or that the world was purpose-built to accommodate human beings: "The child, like a sailor cast forth by the cruel waves, lies naked upon the ground, speechless, in need of every kind of vital support, as soon as nature has spilt him forth with throes from his mother's womb into the regions of light." There is no reason to set humans apart from other animals, no hope of bribing or appeasing the gods, no place for religious fanaticism, no call for ascetic self-denial, no justification for dreams of limitless power or perfect security, no rationale for wars of conquest or self-aggrandizement, no possibility of triumphing over nature. Instead, he wrote, human beings should conquer their fears, accept the fact that they themselves and all the things they encounter are transitory, and embrace the beauty and pleasure of the world.
P.S. 1 Oct: In a review of The Swerve by Stephen Greenblatt's, Sarah Bakewell quotes Poggio Bracciolini, who discovered a complete manuscript of De Rerum Natura in 1417:
Gold, silver, jewels, purple garments, houses built of marble, groomed estates, pious paintings, caparisoned steeds and other things of this kind offer a mutable and superficial pleasure; books give delight to the very marrow of one’s bones. They speak to us, consult with us and join with us in a living and intense intimacy.