After the Ice Age, hunting and foraging communities evolved to a more settled, agricultural life; belief in savage animal spirits was replaced by a belief in domesticated spirits. With the invention of cuneiform and other writing systems, mythological epics emerged to explain the origins of life and the causes of death and earthly suffering. Sumeria, Persia, and Egypt were early centers for these developments. Egyptians were typically obsessed with the afterlife, emphasizing pyramids, mummies, hieroglyphs, spells, prayers, and myths (such as the death and resurrection of Isis). The sea-going Phoenicians spread their alphabet and religion around the Mediterranean, and their gods (El, Baal) especially influenced the Hebrews. When the Indo-Europeans (ancestors of the Greeks, Romans, and others) expanded beyond central Asia, these war-like peoples brought forceful and powerful gods. Their storm god was later known as Zeus (Greeks), Jupiter (Romans), Thor (Germanic tribes), and by other names as well. After Bronze Age civilization collapsed in about 1200 BCE, Greek population declined by up to ninety percent; the survivors preserved the glorious memories of the Bronze Age in myths and epic poetry. Where Homer celebrated the events of the Trojan War in the Iliad and Odyssey. Hesiod described the world's creation in his Theogony. Greeks had a flood myth and dozens of myths celebrating bronzeworking; they especially emphasized the intellect in stories about wisdom and intelligence. Art and drama dominated Greek religious devotion by exploring the glories and dilemmas of human existence. The Romans conquered Greece in 146 BCE, and they adopted or interpreted the Greek gods in typically Latin ways. The epic poet Virgil (in the Aeneid) presented a mythological past as the pre-destined antecedent of Rome's later greatness; the Romans also closely associated statecraft and religion. From within the sprawling territories of the Roman Empire would emerge the three great religions of the Western world: Judaism, Christianity, and Islam. Myths rely on imagination and intuition; they express fervently-held convictions about the ultimate nature of things. Myths are vehicles that capture our most profound ideals and beliefs, and they shape our standards, goals, and self-perceptions.