The period covered is marked by several turning-points, such as the spread of iron technology, the introduction of innovative irrigation systems and the development of new forms of urbanization. In China, India and the Mediterranean, in Central America and in parts of South America, the so-called 'Classical cultures' rose. For the first time, science attempted to develop independently of myth and religion, as a new method to explain nature and human destiny. But this period also witnessed the rise of universal religions such as Buddhism, Hinduism, Christianity and, in the seventh century, Islam.