The earliest evidence of glassmaking includes objects such as beads, pendants, and inlays that were cast in open molds, but glass may have initially occurred as an accidental byproduct in the workshops of Bronze Age metalworkers and ceramicists. While archaeologists have found glass artifacts produced by the Egyptians and Phoenicians dating back to the second millennium BCE, current theory suggests that the first human-made glass dates back even further, to Mesopotamian craftsmen during the third millennium BCE, some 4,000 to 5,000 years ago.