Brian Thomas

Biomedical research uses second-harmonic generation (SHG) imaging to visualize collagen in situ, without fluorophores. The application of this imaging technique to ancient specimens remains largely unexplored. For the first time using SHG, Medieval, Pleistocene and Mesozoic bone samples s were imaged to explore the applicability of SHG to ancient bone from a variety of ages, settings, and taxa. The results suggest that differences in taxa (n = 7) may have very little effect on bone collagen preservation. Variations in settings (n = 7) seem to play a major role in preservation. Higher temperatures accelerate decay, and stable humidities and temperatures support molecular longevity. Generally, a precipitous decline in bone collagen density occurs soon after burial, after which collagen content either vanishes or enters an extremely slow decay regime. Finally, SHG appears to capture very faint traces of endogenous bone collagen, even in samples from which extraction protocols yield no collagen.