A new study refines radiocarbon dating of marine remains and significantly improves the precision with which the human past of the Magdalenian period in the Cantabrian region of Spain can be reconstructed, a key phase of European prehistory dating to around 18,000 years ago. The international study led by the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona (ICTA-UAB) published in the journal Radiocarbon provides new correction values for the radiocarbon dating of marine remains—such as shells—recovered from archaeological sites in the northern Iberian Peninsula.