Heraldry for the DeadIn the late 1800s, archaeologists began discovering engraved stone plaques in Neolithic (3500 2500 BC) graves in southern Portugal and Spain. About the size of one's palm, usually made of slate, and incised with geometric or, more rarely, zoomorphic and anthropomorphic designs, these plaques have mystified generations of researchers. What do their symbols signify? How were the plaques produced? Were they worn during an individual's lifetime, or only