Maguelonne Toussaint-Samat, in her book, History of Food, points out that the presence of oysters in ancient Greek society may be detected in the word "ostracism." In the early sixth century BCE, the Athenian statesman Cleisthenes instituted a constitution for Athens. Included in this was a process intended to prevent the possibility of tyranny, in which the governing body would vote to remove undesirable persons -- that is, those who had the potential to become tyrants -- from its midst. Once a year, at a meeting convened for the purpose, each person present would write the name of his candidate for exile on an oyster shell (ostrakon), and when the results were tallied, if any man garnered enough votes, he was sent out of the region for ten years. Eventually, clay shards took the place of the shells, and the period of exile was shortened to five years.