| Abstract: The study of life’s origin, evolution and distribution in the universe involves many questions that seem unsolvable on first inspection; a familiar example concerns the body temperatures of the dinosaurs: Should we look at their fossilized skeletons and imagine vigorous, warm-blooded, bird-like animals, or plodding, sedentary reptiles like modern alligators? This question has often been approached through qualitative arguments based on phylogeny, histology, ecology and other loose correlatives with metabolism — disappointing if you want the kind of direct and quantitative data a veterinarian might gather with a well-aimed thermometer.
Recent advances in studies of the chemical physics of isotopes has provided surprisingly nuanced and precise answers to this question. Well-preserved tooth enamel and egg shells of dinosaurs and other ancient vertebrates contain carbonate groups (CO3-2) that were drawn from their host’s blood stream and represent fossil remnants of their metabolic chemistry. The heavy rare isotopes, 13C and 18O, are present as trace substitutions in these carbonate groups, in amounts that reflect a variety of factors, such as diet and local climate. But the state of organization of those rare isotopes — their propensity to ‘stick’ to one another with a shared chemical bond as opposed to being randomly scattered across a population of molecules — is controlled by the temperature dependent changes in vibrational energy caused by isotopic substitution. I will present the latest discoveries revealed by exceptionally sensitive and precise measurements of isotopic ordering in fossils of ancient vertebrates, revealing their body temperatures and informing inferences regarding their metabolism, physiology, lifestyle and ecology. |