Marduk was the most important god of ancient Babylonia. After he had defeated Tiamat, he created the earth and the heavens from her corpse. As a result of this grand victory, Marduk was accepted as king of all other gods.
One of his first acts as ruler of the gods was to create mankind. However, this was no act of altruism. Marduk created humans to perform all heavy labor so that the gods may rest.