title: Collagen remnants in ancient bone
Creators: name: Thomas, BD
Publisher: name: University of Liverpool Repository
Year: 2019

description: Ancient bone collagen retains valuable information. Radiocarbon dating, thermal dating, species identification, cladistics analyses, and paleodietary reconstruction efforts all use bone collagen from ancient samples. Experimentally derived models of the temperature-dependent collagen half-life and thus of collagen’s expected shelf life under optimum preservation conditions currently stand at odds with literature reports of collagen remnants in bones with great apparent ages. These issues cause debate about bone collagen longevity. The situation highlights a need to better understand bone collagen preservation conditions and thus to apply new analytical tools to ancient and modern bone samples. In response, this study applies established techniques to ancient bone for the first time. Appropriate samples of ancient bone were first collected and catalogued. They include specimens ranging from Medieval to Paleozoic settings and involve partnerships with six permanent repositories. This thesis describes the novel application of second-harmonic generation (SHG) imaging, an established technique in biomedical science, to ancient bone. In this study, four separate and independent techniques confirmed that SHG reliably detects trace amounts of collagen protein in certain Medieval and Ice Age bone samples. Additional results indicate that SHG detects faint traces of collagen in unexpectedly old bone samples, including dinosaur bones. The technique demonstrated a high degree of sensitivity to small amounts of collagen, plus the potential to explore the micromorphology of collagen decay in bone and other collagenous tissues. The second novel application was Fourier-transform infrared (FTIR) spectroscopy. Recent studies demonstrated its usefulness for bone collagen content estimates in forensic analyses of bone remains. This study extended its application to Medieval, Ice Age, Cretaceous, Jurassic, and Devonian samples and found a general trend of diminishing collagen signal with older bones. FTIR was also used for the first time to assess bone collagen integrity in an artificial decay experiment. In addition, the applicability of Raman spectroscopy to ancient bone was explored. Accelerator mass spectrometry (AMS) was also used to measure stable and unstable carbon ratios in many of the same ancient bone samples used above. AMS 13C results brought forth two main conclusions. They confirmed the accuracy of preliminary results obtained using a recently developed portable quadrupole mass spectrometer (QMS) to detect stable isotopes including 13C and 12C ratios from the bioapatite fraction of Medieval bone. They also confirm for the first time a co-occurrence of primary (i.e., original to the organism) isotopic signatures in fossil bones with primary organic signatures. Analysis of published Cretaceous vertebrate fossils with biological stable isotope ratios matched this co-occurrence. Finally, the first AMS 14C results from Cretaceous bone collagen are presented. 14C results discriminated between modern, medieval, Roman era, and ice age, but not between Cretaceous and Jurassic time frames. Overall results suggest that the application of novel techniques like SHG will help detect and further characterise ancient bone collagen. Also, low cost, nearly nondestructive tools like FTIR and QMS show promise to aid continued discoveries of original isotope ratios and biological remnants like bone collagen in fossils from widening geographic and geological ranges.