Scientists Issue 'Words of Warning' After Strange Discovery in Danish Skeletons

Key Points:

• Scientists from the University of Southern Denmark have identified that radiocarbon dating of medieval human remains can be skewed by the "freshwater reservoir effect," causing bones to appear centuries older than they actually are.
• This effect occurs because fish-heavy diets incorporate older carbon isotopes from freshwater sources, which have lower carbon-14 levels compared to the atmosphere, leading to misleading radiocarbon dates.
• Analysis of 27 skeletons from Danish monasteries revealed some bones dated decades or centuries before the monasteries were built, correlating with elevated nitrogen-15 levels indicative of freshwater fish consumption.
• The researchers warn that this phenomenon likely affects archaeological findings beyond Denmark and recommend measuring nitrogen-15 isotopes to identify and correct for the freshwater reservoir effect in dating bones.
• Accurate calibration models exist to adjust radiocarbon dates when freshwater reservoir effects are detected, improving the reliability of dating in regions where fish was a significant dietary component, especially during medieval times.