MEGA14C: a database of radiocarbon dates from Holarctic mammal collagen purified with high-quality chemistry

DATABASE: MEGA14C is a comprehensive dataset of late Quaternary Holarctic mammal AMS radiocarbon measurements (fossil ages). The majority of dates (93% / 10,858 records) were obtained from collagen purified using ultrafiltration, with an additional 6% (743 records) from XAD-2 purification and less than 1% (86 records) from hydroxyproline isolation. In total, the database includes 11,715 radiocarbon determinations spanning 8 orders, 23 families, 78 genera, 133 species and 18 subspecies. 83% are from taxa with maximum body mass exceeding 44 kg, 27% are from extinct vertebrates, and 14% are from domesticated species. Where available, each record is supplemented with geolocation, genetic and isotopic information. Reporting of chemical pretreatment is critical for interpreting dating accuracy and reproducibility; however, 44% of published dates originally lacked this information. We addressed this omission through more than 10,000 personal communications with researchers and AMS laboratories, ensuring the dataset is as complete and reliable as possible. MEGA14C should support (pre)historical research and provides a foundation for future expansion and/or integration into a global radiocarbon repository. In a companion study (https://doi.org/10.1002/jqs.70012), we outline the broader challenges posed by the lack of standardized and transparent collagen pretreatment reporting, how inadequate reporting standards for radiocarbon results and collagen chemistry impede the effective curation of chronological datasets, and advocate for international solutions including open and replicable protocols, facility-led documentation and a global radiocarbon database.