Cod bones tell tales

"Fish heads, fish heads..." A recent study of European cod bones shows that "cod were exploited in the Middle Ages from many, often distant, fishing grounds, with an international trade in dried stockfish." The fish were much larger in medieval times, and began to began to be traded around the year 1000 C.E.

The study, by scientists from Britain, France, Belgium, Germany, Scandinavia and the Baltic states, analyzed fish bones for their stable-isotope content.

The distinctly reduced size of modern fish has been attributed to over-fishing.