Bronze Age civilizations were similar in that:
(a) They all grew around river valleys,
(b) Each had an organized political and social system, e.g., monarchies and Republics and division of society into higher and lower classes.
(c) Each practiced trade and commerce, e.g., Harappa with Mesopotamia
(d) Each developed complex religious beliefs, e.g., worship of multiplicity of Gods, belief in life after death, nature worship, totems, oracles, etc.
(e) Each developed a writing script, e.g., Cuneiform of the Mesopotamians, Hieroglyphic of the Egyptians and Pictographic script of Chinese
(f) Each civilization contributed in its own special way to progress in science, mathematics, art, architecture, literature, astronomy, medicine, law and formation of the government.