Proteins persist longer in the fossil record than DNA, but the longevity, survival mechanisms and substrates remain contested. Here, we demonstrate the role of mineral binding in preserving the protein sequence in ostrich (Struthionidae) eggshell, including from the palaeontological sites of Laetoli (3.8 Ma) and Olduvai Gorge (1.3 Ma) in Tanzania. By tracking protein diagenesis back in time we find consistent patterns of preservation, demonstrating authenticity of the surviving sequences. Molecular dynamics simulations of struthiocalcin-1 and -2, the dominant proteins within the eggshell, reveal that distinct domains bind to the mineral surface. It is the domain with the strongest calculated binding energy to the calcite surface that is selectively preserved. Thermal age calculations demonstrate that the Laetoli and Olduvai peptides are 50 times older than any previously authenticated sequence (equivalent to ~16 Ma at a constant 10°C).DOI:
http://dx.doi.org/10.7554/eLife.17092.001
Sparse records and discontinuous and/or poor chronologically resolved data hinder 2 construction of reliable palaeoenvironmental sequences for the interior of South Africa. Wonderwerk Cave occupies a central position in the interior where the Kalahari 4 Thornveld/dry woodland vegetation and generally arid conditions are expected to be sensitive 5 to subtle past climate perturbations, and evidence from this site has been key to forming views 6 on environmental change in the interior. A compilation of existing data including principal 7 components analysis of pollen suggested broad trends ranging from variably arid and open in 8 the early Holocene to moister conditions from about 7500 to 5000 years, followed by aridity 9 thereafter. In an effort to better establish the nature and timing of shifts from the late 10 Pleistocene sequence onwards we analyse carbon and oxygen isotope ratios in a robust sample 11 of ostrich eggshell from Wonderwerk Cave. The resulting data are then placed within a 12 temporal framework established by Bayesian modeling of existing radiocarbon dates, and 13 compared against shifts in the Wonderwerk cultural sequence. Several shifts and trends in 14 aridity include an arid to moist shift in Layer 4b near 6000 years coincident with a cultural 15 shift within the Wilton assemblage, and thereafter an aridification trend culminating at about 16 2000 years with the appearance of the Ceramic LSA.
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