<span>The first four civilizations arose in river valleys that made irrigation, and, hence,</span><span> ...</span><span>Bands of hunter gatherers, significant equality between sexes</span><span> ... </span><span>The Neolithic Revolution</span><span> ... </span><span>Agriculture freed up labor, metal-working one such result</span><span> ..... </span><span>The narrower view suggests that the chief difference between civilizations and other
