Human Evolution Beyond Collagen

Many ancient hominin fossil bones have been recovered from cold and stable environments that preserve DNA and collagen. Yet, in the (sub-)tropics, there is a scarcity of genetic and chronological evidence associated with early humans. Crucial bones, essential to our understanding of human evolution, sadly, exhibit minimal DNA or collagen due to protein degradation. Current dating methods focus on collagen, a protein prone to deterioration in warm, humid areas. HUMEVCOL aims to revolutionise the analysis of heavily degraded fossil bones by pioneering a technique to extract and radiocarbon date different proteins called gamma-carboxyglutamic acids (Gla)-containing non-collagenous proteins (NCPs), enabling dating of significant early faunal and Homo sp. fossils from tropical regions. Past attempts to date NCPs encountered obstacles. Experiments in the 1990s revealed conflicting dates between collagen and osteocalcin (OC), a Gla-containing protein within bone. Surprisingly, OC dates appeared older than collagen, contrary to expected results due to environmental contamination. Technical issues arose due to the fragmented nature of the extracted OC, complicating accurate detection and dating. Recent studies revealed Glas potential preservation within the bones inorganic phase, particularly within crystal aggregates. These have preserved DNA in some fossils, indicating they may also retain NCPs, suggesting that the decline of collagen in bone might not directly correlate to a simultaneous decrease in OC. Our proof-of-concept study showed that Gla, in fact, survive in Pleistocene bone, when a newly developed extraction protocol is followed. Other challenges include the relatively small amount of these proteins in bone and its upscale for dating, particularly in poorly preserved samples. Technological advancements offer hope for overcoming these challenges. Modern methods can potentially isolate and date Gla, eliminating the reliance on intact OC. Thus, our objectives are to (1) comprehend bone degradation (diagenesis) on a structural and mechanistic level; and (2) to identify a collagen-independent technique to radiocarbon dating fossils. To achieve this, we will establish a comprehensive baseline data, examining key diagenetic parameters through mass spectrometric imaging, infrared spectroscopy, and C:N ratios. Modeling will be employed to predict environments preserving NCPs within bone. A non-carbon-based extraction protocol for Gla will allow us to capture and date it, providing environment-independent information from degraded fossil bones. This will dramatically enhance the analysis and dating of key archaic remains. Our research will be conducted on the faunal remains from the Denisova Cave (Russian Federation), Fuyan Cave (China), and from important Palaeolithic sites in the tropics including Fa Hien and Kitulgala Beli-Lena caves (Sri Lanka), and the Liang Bua Cave site of Homo floresiensis (Flores, Indonesia).