Compound-specific approach to the δ13C analysis of cholesterol in fossil bones

δ13C values for cholesterol isolated from fossil animals, namely those of whales dated at 9735 ± 160 yr and 75000 ± 15000 yr B.P., are reported. Gas chromatography (GC) showed that 12 and 15 μg of cholesterol per gram dry weight of bone were recovered from the bones of these two fossil animals, respectively. Conventional gas chromatography-mass spectrometry (GC-MS) confirmed the identity of the ancient cholesterol and that the peaks separated by GC were of high purity. Gas chromatography-combustion-isotope ratio-mass spectrometry (GC-C-IRMS) of cholesterol recovered from the fossil specimens yielded δ13C values that plotted within the range expected for the bulk fat of marine mammals. Significantly, the isotopic depletion between the cholesterol and collagen was similar for both ancient and modern whale bones, indicating reliable preservation of the δ13C signal between the ancient cholesterol and the protein constituents. The potential to derive δ13C values from individual lipids, for which the carbon skeletons are completely unaffected by decay processes, significantly extends the scope of palaeodietary studies.