Collagen survival and its use for species identification in Holocene-lower Pleistocene bone fragments from British archaeological and paleontological sites

Proteins have long been known to persist in Quaternary bone fossils and are often targeted as a source of carbon used in radiocarbon dating and stable isotope analyses for determining provenance and obtaining dietary information. We have previously reported a technique using the dominant structural protein collagen (type I) as a source of genetic information for species identification in modern and relatively young (Holocene) archaeological samples. We report a systematic investigation of amino acid composition and collagen peptide mass fingerprints (PMF), for a range of samples dating back approximately 1.5 million years. Extrapolation from high temperature experimental decomposition rates predict that at a constant 10°C (the approximate mean annual air temperature in Britain today) it will take between 0.2 and 0.7 Ma for levels of collagen to fall to 1% of their original concentration in an optimal burial environment. Even when the glacial intervals of the British Quaternary are factored into the temperature calculations, the more conservative of these two estimates extends the range for collagen sequencing to the Lower Pleistocene as confirmed by the presence of collagen peptides in bones from the Weybourne Crag (~1.5 Ma). Collagen fingerprinting can extend the range of identifiable taxa present at sites with large assemblages of fragmentary bone material such as that encountered at the ~900 Ka site at Happisburgh (Norfolk, UK) recently identified as showing signs of the earliest humans in Britain.