The Americas had meanwhile become the seat of complex societies that fully deserve the epithet “civilized”. Generally speaking, the level of mastery over the environment attained in Mesopotamians and Egyptians had achieved by about 2500 B.C. A four-thousand-year lag was far too great for the Amerindians to make up when the Spanish conquistadors burst in upon their seclusion. Since the higher culture of the Aztec and Inca empires left only limited traces behind, we can afford to be quite cursory in our consideration of the Amerindian civilization.