Wisdom teeth: refining our understanding of mammalian evolution through dating dental enamel

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Directly dating mammal fossils older than the limit of radiocarbon dating (~50,000 years) is very challenging, and this has led to a research focus on the most recent past in forming our understanding of mammalian response to changing environments. However this narrow time window is extremely limiting if we aim to understand the effects of climate change on land-based organisms, or unpick our own evolutionary history. We are hard-pressed to pinpoint the major evolutionary drivers for African mammals, and to compare patterns across a large, diverse continent. This problem notably includes our own ancestors. The fundamental problem preventing the required comparisons is chronology, and specifically a method that can date fossils directly. Our project team has been developing and employing methods for dating using the breakdown of the original proteins trapped within fossils. Excitingly, we have just made a methodological breakthrough which enables amino acid (a protein breakdown product) dating to be undertaken on the small amounts of amino acids remaining in tooth enamel (a resistant crystalline material composed of calcium phosphate with small amounts of protein). Dating enamel has the enormous advantage of providing a direct date on mammal teeth (critical fossils of interest) and the new method now enables routine amino acid analysis, successfully dating UK material up to 3 million years in age. This technique is ripe for development to a range of mammalian species and additional geographic regions, potentially revolutionising our understanding of mammalian evolution (including humans) during the last few million years, and their response to environmental change, at the local and the global scale.This proposal will address the three areas of technology development needed for this dating method to be used routinely, but the time frame it opens up (the last ~4 million years) will enable a significant shift in the range of research questions we can address. The three strands of technological advance proposed are: 1) a microfluidics ("lab on a chip") approach, which will enable both a significant decrease in the physical sample size needed, as well as preparation / analyses to be undertaken outside specialist labs; 2) combining analysis and imaging of both the organic and inorganic fractions to understand their structure, function and any impact on the protein breakdown; and 3) using advanced chemical models to understand the breakdown reactions.We will then apply these methods to two regions of Africa of particular evolutionary interest: east Africa (including the Rift Valley) and southern Africa (including the 'Cradle of Humankind'). Initially calibrating the dating approach on reliably dated material, we will then expand it to material that is currently of unknown age. The developed chronology will also enable models of human-environment interaction to be tested, providing a breakthrough in our understanding of our evolutionary past. This project will therefore take the latest advances in dating and apply them to a region where the palaeoenvironmental record can help shape the understanding of the sensitivity of Africa's biota (plants and animals) to changes in temperature and rainfall patterns. Understanding large mammals' responses to environmental and climate change is critical for developing appropriate conservation measures, and we will also gain insights into the timings and drivers of the evolution of our human lineage.