American maize in the Canary Islands: the Columbian exchange measured in bone chemistry

The Canaries are usually a waypoint in this story - the last watering stop before the Atlantic. Isotopes in 66 skeletons from Gran Canaria turn the islands into the measuring instrument instead. Before the conquest the diet was Mediterranean barley and wheat; by the eighteenth century American maize supplied about two thirds of the carbon in island childhoods, and the granary returns agree. The same record holds the people the change was built on.