Like their mollusk colleagues the clams, oyster shells can keep climate records in the composition of their shells. Oysters recently informed scientists about a key moment in American history--the settlement of the Jamestown colony in Virginia in 1607, and its first few trying years.

The colonists' records suggested that they encountered a hostile environment; oyster shells confirmed that the colonists experienced a worst-in-a-millennium drought upon arrival, worsening an already tough situation. Archaeologists found the shells in a Jamestown trash dump where the colonists threw out their kitchen trash. The 400-year-old shells show that the James River was saltier back then, which shows that there was little rainfall to recharge the supply of fresh water.