"Achilles, Odysseus, and the other heroes of Homer's Iliad and Odyssey fought with shields and swords of bronze. What was the world like in those mythic days, when the rival Greek cities of Troy and Mycenae battled for supremacy, and, far to the west, unknown engineers raised the megaliths of Stonehenge? What do we know of even earlier times, when the settled peoples of Europe first replaced their crude stone tools with those made of refined metal, and crafted ornaments of beaten copper and gold?".