We investigate anomalously recent 14C ages on some human skulls from the Late Neolithic gallery grave at Altendorf, Hesse, Germany (∼3200 cal BC). Most Altendorf skulls give apparently accurate 14C ages, but offsets of up to 1500 years affect around a quarter of those sampled. These skulls were apparently conserved with a consolidant not applied to other skulls, which we were unable to remove, identify or detect, except by its impact on 14C ages. This consolidant is invisible in collagen ATR-FTIR spectra, and must have similar δ13C, δ15N and C/N values to human collagen. It must be a glue made from bone or skin, which is effectively collagen, but biomolecular methods that have identified modern bone/hide glues elsewhere have not found non-human biomarkers in the Altendorf samples. This has implications for research on museum objects with incomplete conservation records, particularly in cases without the possibility of replication and independent age controls available at Altendorf.
