Improving the chronology of early human evolution

Lead Research Organisation: University of Oxford
Department Name: School of Archaeology

Abstract

The Turkana and Awash basins in the East African Rift, preserve an exceptional fossil and archaeological record and to a large extent, form the basis for our current understanding of early hominin environments. Ancient volcanic activity has left numerous ash deposits (tuffs) that can be dated using the radiometric dating method 40Ar/39Ar. Although precise, dates obtained by this method only provide broad envelopes with significant temporal gaps because volcanism is episodic, and tuffs do not always survive across the landscape. Furthermore, despite the abundance of archaeological finds and animal fossils in this region, datable tuffs are rare in the East African Rift. Consequently, age estimation often relies on imprecise relative methods, such as magnetostratigraphy and biostratigraphy. A method for obtaining absolute dates is urgently required in order to correlate all the sedimentary sequences within the eastern rift, as well as across Africa, and to help clarify the wider picture of early human biological and cultural events during the Plio-Pleistocene. Likewise, the South African sites also suffer from dating problems, albeit from different issues. In most of these cases they are karstic infills and only recently, have any absolute methods based on cosmogenic and uranium/lead isotope systems been applied. These techniques also leave huge gaps and/or do not precisely date the fossil or archaeological event of interest. For instance, U/Pb dates generally reflect the ages of over- or underlying flowstone and not that of a fossil.

We propose to apply a novel luminescence-based method known as infrared-radiofluorescence (IR-RF), which the named researcher co-investigator on this proposal helped to develop, in order to determine the age (i.e. time of deposition) of fossil- and artefact-bearing sediments and/or volcanic tuffs in Kenya, Ethiopia and South Africa and to fill in the time gaps omitted by radiometric techniques. The IR-RF method is widely applicable due to the ubiquitous occurrence of sand sized feldspar mineral grains required for dating and the technique targets potassium- (K-) rich feldspar, one of the most common types of mineral on earth. Recent studies suggest that this methodology has the potential to extend the age range of luminescence dating from 0.5 million years to 4 million years, thus encompassing the majority of the time range over which the human family evolved.

Methods of recording and analyzing luminescence data have developed significantly over the last five years, including improved light detection and more advanced analytical and statistical techniques, all of which have led to new approaches and more flexible ways of processing and visualizing data. Recent technological advances including the development of single photon imaging systems based on electron multiplying charge coupled devices (EMCCD) also suggest that the time is right to bring together and apply some of these new cutting-edge innovations to help achieve more reliable chronologies for early hominin evolution.

This research will dramatically increase the number of well-dated sequences in areas archiving key evidence for early human evolution and it will enable us to provide significant improvements in correlating human fossil records across Africa. A new and more refined chronological framework will greatly improve our understanding of the diversity of adaptive challenges faced by early hominins since the Pliocene and it will help to shed more light on the hotly debated question of the role of climatic and ecological changes in driving hominin evolution.

Planned Impact

The record of past climate change and its impacts on human evolution provides an ideal context for considering issues surrounding human adaptability, the effects of future climate change, and the response of our species to environmental change. Although, research into chronology and past environments is of no immediate commercial value, it seeks to understand events and processes that despite being lost in time, are of deep interest to most people. We believe that our research can provide a very powerful tool for education and public engagement and we wish to focus the impact of our work on science enrichment. In particular, we would like to target children of primary school age, based on the premise that our research can provide a good vehicle for showcasing how science 'works', and how we know what we think we know. We will develop an educational resource for schools which can be made freely available as a download from our project website. In conjunction with our project partners in the field, we will also seek to directly engage with primary schools situated in the vicinity of our archaeological sites in Kenya, Ethiopia and South Africa by organising visits, giving talks and participating in activities with the children and their teachers. The proposed study will hopefully benefit such local communities for whom cultural heritage relating to human prehistory is a matter of local pride but whom we feel are significantly under-served in current efforts to disseminate scientific knowledge whilst at the same time, being held responsible for taking care of globally important archaeological sites.

Our research in geochronology will also directly add value to fossil collections housed within national institution, and it has the potential to transform the archaeological and geological heritage of each country by providing critical context to many previously undatable collections of fossils and archaeological remains. We are particularly keen to build bridges between higher education and research institutions and we will seek to strengthen collaborative networks between research groups spanning the European and African continents. The project links the major fossil repositories of various countries including the National Museums of Kenya and the Maropeng Visitor Center in the 'Cradle of Humankind World Heritage Site' in South Africa. We are convinced that the proposed new luminescence dating methodology can have a similar impact on human evolutionary studies as the radiocarbon revolution had on archaeology. Although, this project will by no means solve all of the many dating issues, it will aim to provide a template and guidance for how to approach this kind of chronometric work and we expect it to leave a long lasting legacy. We aim to provide site-based data illustrating the power of our new methodological approach and to document our research with powerful case studies representing best practice in the field. To facilitate intellectual exchange between each community, chronological and environmental databases will be made freely available on the Oxford based ORAU Data Service databases (see data management plan). Our academic publication plan will see publications across a range of geology, physical and archaeological science journals. This will demonstrate the opening of a considerable research frontier that can reflect the diversity of analytical work needed to fully understand the driving forces behind human evolution.

Publications

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