New research published in the Journal of Archaeological Science has utilized a refined Beryllium-10 cosmogenic surface exposure dating methodology to pinpoint the construction of megalithic henge monuments in Portugal's Alentejo region. The study, released on April 10, 2026, suggests these structures were erected roughly 500 years earlier than previously estimated, placing their origin in the mid-5th millennium BCE.
By measuring the accumulation of cosmogenic isotopes on the upper surfaces of the granite monoliths, researchers were able to bypass the uncertainties of traditional radiocarbon dating of associated organic matter. This breakthrough allows for a more precise synchronization of Neolithic social complexity with shifting paleoclimate records, highlighting a period of intense monument building during a phase of sudden environmental stability.