TEL AVIV, ISRAEL—Early hominids routinely recycled the stone and bone objects they used every day, according to the archaeologists gathered at “The Origins of Recycling,” a conference recently held at the University of Tel Aviv. Evidence of the reworking of old flint tools 1.3 million years ago has been found in southern Spain, and Neanderthals refashioned bone tools at a butchering site near Rome some 300,000 years ago. Additional sites have been found in Israel and North Africa. Recycling conserves energy and raw materials, but did early humans decide to conserve resources, or did they just pick up old tools unconsciously when it was time to make something else?