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

Lead Research Organisation: University of York
Department Name: Chemistry

Abstract

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.

Planned Impact

This project will develop and apply a dating method using microfluidic technologies, reducing sample sizes and widening its applicability, democratising the technology by reducing the resource requirements for effective analysis. The development of a better dated palaeo-record has the potential to improve our understanding of our past evolution (and thus better contextualise our ancestry and heritage), as well as providing data on past climate and any faunal impact.

The key non-academic beneficiaries of this project are therefore:

Future generations of researchers and interested lay people: Currently, direct dating of mammalian fossils requires sample sizes > 15 mg, which for the most important specimens can cause significant damage or restrict the use of such techniques, thus limiting the sample's scientific value. Reducing the amount of sample needed for analysis using microfluidic technologies will improve long term preservation of material for future generations, while also developing the knowledge base from which they can learn.

Socioeconomically disadvantaged groups in Africa: The collaborative approach of this research aims to use the technologies developed over the course of this project to teach students and staff from socioeconomically disadvantaged groups in Africa, promoting the relationships between regional institutions and local communities concerned with local heritage enhancement and protection (e.g. the South African Heritage Resources Agency (SAHRA)). This will enable members of these communities to engage more deeply with the projects that use samples collected from their locations, both empowering them and potentially providing useful skills improving future employment prospects in this field.

Museum and festival visitors (UK & Africa): The project team has collaborations with museums in Yorkshire, London and Cape Town, and will develop events and activities to engage visitors at these institutions. Where new evidence emerges using this approach, presentation of this new material challenging existing theories will also be included. This will increase visitors' knowledge of the history of the Quaternary and aid their understanding of the heritage of humans and other species throughout this period. Potential future exhibitions could also focus on the technology itself, leading to increased interest in the ways in which science can support archaeology and history. The research's relevance to understanding climate is a key area where increasing public understanding is essential. The team has extensive experience in developing science festival outreach events and activities, including workshops, public lectures and hands-on family events.

Science education (UK & Africa): Engaging school students in science by showing them the application of science in understanding our past (archaeological, evolutionary and climate) can be a revelation; they have often not seen this type of more unusual application of science, and can more easily relate it to their lives and interests. We will develop our work with the Education department at York focused on teacher-training, using the application of science to the study of our past to engage PGCE students and schools. This will build science capacity, especially in Africa.

Governments / NGOs developing conservation strategies: models used to predict our current/future climate and ecology rely on our understanding of the past. The insight into past mammal response to changing environmental conditions will help inform conservation strategies, taking account of the widest possible range of factors and influences.

Health sector and other commercial organisations: the developments made in microfluidic technology could have relevance to industry; analysis of biological molecules in low concentrations from complex mixtures is a highly active area for commercial development, particularly in development of analytics for continuous biomanufacturing.

Publications

10 25 50