There are many similarities and differences between early civilizations that developed in Mesopotamia, Egypt, India, and China. For instance, most of Mesopotamia and China's Government structure was made up of city-states, while Egypt was made up of dynasties. According to their religous practices, Mesopatia mostly practiced aminism, which is the worship of multiple gods. Egypt also worshipped multiple gods and believed in the afterlife. India consited mostly of animal worship, and China believed in cosmology and the "mandate of heaven". There are many other major differences in these cultures, such as their accomplishments. Mesopotamia created the first unified empire (Akkadians) as well as the first writing system (Sumerians). Egyptians are famous for the Book of the Dead and hieroglyphics. China is well known for the appearance of social classes and bronzes.
There were many developments that took place in the first millennium BCE. One major development was the invention of iron, Another was the spread of Christianity. Christianity had become a powerful religion after spreading to northern and eastern Europe, the Americas, and parts of Asia and Africa. Each of the religions of these civilizations responded to a crisis in the society of the ancient world, and the religious developments would reconnect ethics to history and restore order to society. The appearance of iron lead to better weapons, tools, and powerful armies. Many different philosophies began to rise in the first millennium as well. In China, Confusioism, Daoism, and legalism were major philosophies that were significant. In India, there were Buddhism, Hindu, and focuses on the cycle of re-birth and re-death. The development of iron and new visions of social and political order contributed to these many new ideas and developments of the first millennium