Change of diet of the Greenland Vikings determined from stable carbon isotope analysis and C-14 dating of their bones

Bone samples from the Greenland Viking colony provide us with a unique oppo rtunity to test and use C-14 dating of remains of humans who depended upon food of mixed marine and terrestrial origin. We investigated the skeletons of 27 Greenland Norse people excavated from churchyard burials from the lat e 10th to the middle 15th century. The stable carbon isotopic composition ( delta(13)C) Of the bone collagen reveals that the diet of the Greenland Nor se changed dramatically from predominantly terrestrial food at the time of Eric the Red around AD 1000 to predominantly marine food toward the end of the settlement period around AD 1450. We find that it is possible to C-14-d ate these bones of mixed marine and terrestrial origin precisely when prope r correction for the marine reservoir effect (the C-14 age difference betwe en terrestrial and marine organisms) is taken into account. From the dietar y information obtained via the delta(13)C values of the bones we have calcu lated individualreservoir age corrections for the measured C-14 ages of eac h skeleton. The reservoir age corrections were calibrated by comparing the C-14 dates of 3 highly marine skeletons with the C-14 dates of their terres trial grave clothes. The calibrated ages of all 27 skeletons from different parts of the Norse settlement obtained by this method are found to be cons istent with available historical and archaeological chronology. The evidenc e for a change in subsistence from terrestrial to marine food is an importa nt clue to the old puzzle of the disappearance of the Greenland Norse, obta ined here for the first time by measurements on the remains of the people t hemselves instead of by more indirect methods like kitchen-midden analysis.