Periodic Reporting for period 2 - EQUATE (Bridging Europe: A Quaternary Timescale For The Expansion And Evolution Of Humans)
Reporting period: 2021-10-01 to 2023-03-31
Our aim in EQuaTe is to establish a timescale for the human occupation of northern and central Europe from 2 million years ago to ~70,000 years ago. This pan-European integration of our rich archaeological record will provide key insights into the dynamics of human populations, and their response to changes in climate.
During the Quaternary period (the last 2.6 million years; Ma) we have had dramatic global climate change; Europe would have seen periodic ice sheet expansion and contraction, impacting on plant and animal communities, likely driving technological adaptations and the evolution and dispersal of human populations.
But beyond the limit of carbon dating, ~ 60 thousand years (ka), our ability to date the human record, the Palaeolithic, is poor. The long history of study of Europe’s geological and archaeological record means that we have an unparalleled archive of climatic changes critical to understanding our human story. But most terrestrial sequences are short, providing just snapshots of time, with little meaning unless the timescale is secure. It is very challenging to link the archaeology to the global record of climate and environmental change, and therefore impossible to test drivers / responses and feedbacks that will help us understand the human story in greater detail.
However, in the last few years, we have discovered that commonly-occurring fossils (snail opercula) have locked up within their crystals two secrets to telling the time. Opercula are sesame-seed-sized parts of shells that the snails use to shut themselves away inside their shells; they are made of a strong mineral called calcite and are often abundant at archaeological sites. They have been collected from hundreds of sites for the last couple of centuries, and now through analytical advances, we can exploit these as time capsules.
Trapped within their crystals (in voids within the crystal structure, known as the “intra-crystalline” fraction), their original protein breaks down predictably, meaning that we can use this intra-crystalline protein degradation (IcPD) to give a relative dating method. The crystals are also able to store a small proportion of the energy that comes from the radioactivity of the sediments in which they are buried. When this stored energy is released in the laboratory it produces light from the crystal, and this is called thermoluminescence (TL). This TL signal gives us a second dating method. Therefore in EQuaTe we are testing both dating methods on the same commonly-occuring biomineral to understand the European archaeological and palaeoclimate record. A key strength of EQuaTe is that we are not focusing solely on archaeological sites; our analysis of material from relevant geological sites deepens our understanding of prey and vegetation communities, enabling us to frame humans within their palaeoenvironments.
EQuaTe has 4 objectives: three of these address key time-periods: the earliest human occupation of northern Europe (2 Ma - 900 ka); tracking the ebb and flow of these populations into the Middle Pleistocene (900 ka - 500 ka); and refining the temporal relationships into the Middle Palaeolithic (500 ka - 70 ka). Opercula are abundant in northern European sediments, and the freshwater ecosystems where they are found played a major role in human migrations, providing corridors into new regions. But through the fourth objective, EQuaTe is also exploring the dating potential for other biominerals, enabling us to expand across a range of environments.
During the Quaternary period (the last 2.6 million years; Ma) we have had dramatic global climate change; Europe would have seen periodic ice sheet expansion and contraction, impacting on plant and animal communities, likely driving technological adaptations and the evolution and dispersal of human populations.
But beyond the limit of carbon dating, ~ 60 thousand years (ka), our ability to date the human record, the Palaeolithic, is poor. The long history of study of Europe’s geological and archaeological record means that we have an unparalleled archive of climatic changes critical to understanding our human story. But most terrestrial sequences are short, providing just snapshots of time, with little meaning unless the timescale is secure. It is very challenging to link the archaeology to the global record of climate and environmental change, and therefore impossible to test drivers / responses and feedbacks that will help us understand the human story in greater detail.
However, in the last few years, we have discovered that commonly-occurring fossils (snail opercula) have locked up within their crystals two secrets to telling the time. Opercula are sesame-seed-sized parts of shells that the snails use to shut themselves away inside their shells; they are made of a strong mineral called calcite and are often abundant at archaeological sites. They have been collected from hundreds of sites for the last couple of centuries, and now through analytical advances, we can exploit these as time capsules.
Trapped within their crystals (in voids within the crystal structure, known as the “intra-crystalline” fraction), their original protein breaks down predictably, meaning that we can use this intra-crystalline protein degradation (IcPD) to give a relative dating method. The crystals are also able to store a small proportion of the energy that comes from the radioactivity of the sediments in which they are buried. When this stored energy is released in the laboratory it produces light from the crystal, and this is called thermoluminescence (TL). This TL signal gives us a second dating method. Therefore in EQuaTe we are testing both dating methods on the same commonly-occuring biomineral to understand the European archaeological and palaeoclimate record. A key strength of EQuaTe is that we are not focusing solely on archaeological sites; our analysis of material from relevant geological sites deepens our understanding of prey and vegetation communities, enabling us to frame humans within their palaeoenvironments.
EQuaTe has 4 objectives: three of these address key time-periods: the earliest human occupation of northern Europe (2 Ma - 900 ka); tracking the ebb and flow of these populations into the Middle Pleistocene (900 ka - 500 ka); and refining the temporal relationships into the Middle Palaeolithic (500 ka - 70 ka). Opercula are abundant in northern European sediments, and the freshwater ecosystems where they are found played a major role in human migrations, providing corridors into new regions. But through the fourth objective, EQuaTe is also exploring the dating potential for other biominerals, enabling us to expand across a range of environments.
In the first 2 years of this project, we have been working with colleagues across Europe to catalogue, collect, prioritise and analyse fossil samples from a wide range of sites. We have generated regional opercula IcPD chronologies for France, the Netherlands, Germany, Poland, Hungary and Switzerland. We have been able to access deep sediment core material from the Pannonian Plain and the Heidelberg Basin and test the temporal range of opercula IcPD, which successfully extends to 2 Ma, therefore confirming that it is able to cover the time periods of human migration and evolution of interest in this region. We have been able to demonstrate temporal resolution within an interglacial warm period (earlier parts of the interglacial are differentiable from later parts), and identify sites where the original chronology was incorrect.
We have characterised the TL signal from biogenic calcite and developed a robust measurement protocol that can be applied to TL dating of opercula, and extended to other biominerals such as slug plates. We have also investigated the reproducibility of TL measurements made on opercula. We have begun analysing mammalian tooth enamel (a calcium phosphate biomineral) of several taxa from palaeontological / archaeological sites in the UK. This has revealed its great potential to date mammalian fossils of Pleistocene age, and to disentangle material from mixed age assemblages.
We have characterised the TL signal from biogenic calcite and developed a robust measurement protocol that can be applied to TL dating of opercula, and extended to other biominerals such as slug plates. We have also investigated the reproducibility of TL measurements made on opercula. We have begun analysing mammalian tooth enamel (a calcium phosphate biomineral) of several taxa from palaeontological / archaeological sites in the UK. This has revealed its great potential to date mammalian fossils of Pleistocene age, and to disentangle material from mixed age assemblages.
There have been three key breakthroughs: (a) widening the range of different biominerals for IcPD; (b) improving the data processing for TL and (c) understanding the IcPD in tooth enamel from different types of animals.
Our work on exploring new biominerals has progressed much further than had been anticipated; we have successfully tested three alternative calcium carbonate biominerals for IcPD behaviour: foraminifera (a marine organism), worm granules and slug plates (both land-based organisms); this will help us extend the dating approaches to a greater range of environments and sites.
We have also developed automated analytical procedures for handling large and complex data sets obtained from cutting edge imaging of the TL signal to look at the variability of the TL signal within individual opercula.
Understanding the way that the protein breaks down in the tooth enamel of different types of animals means that we can target the most useful taxa for dating; those that break down rapidly will be really useful for younger sites, whereas those that break down slowly will be most useful for our older sites.
The data collection so far has provided the foundations for us to link the rich fossil record on land to the global climate signal. Our data shows that integrated temperature differences across the European study area have impacted the extent of IcPD; we will use tie-points from the TL approach and other dating methods to correlate the regional chronologies developed. The primary focus of the first part of the project was on opercula, but for the second part we will continue our expansion to tooth enamel, and to test additional calcite biominerals. As the chronologies develop, we will expand the temporal and spatial range of archaeological sites analysed. This targeted effort will result in a valuable chronology usable across the continent; a completely new type of history with which to test hypotheses about human behaviour. What were the root causes and timings of the evolution and expansion of early humans in Eurasia? Once populations became more established, the rich archaeological record shows apparent differences in tool technologies; but are these a reflection of different species, technical evolution over time, geographical variations in source materials, or cultural tradition? With the EQuaTe timescale, questions like these can finally be tested.
Our work on exploring new biominerals has progressed much further than had been anticipated; we have successfully tested three alternative calcium carbonate biominerals for IcPD behaviour: foraminifera (a marine organism), worm granules and slug plates (both land-based organisms); this will help us extend the dating approaches to a greater range of environments and sites.
We have also developed automated analytical procedures for handling large and complex data sets obtained from cutting edge imaging of the TL signal to look at the variability of the TL signal within individual opercula.
Understanding the way that the protein breaks down in the tooth enamel of different types of animals means that we can target the most useful taxa for dating; those that break down rapidly will be really useful for younger sites, whereas those that break down slowly will be most useful for our older sites.
The data collection so far has provided the foundations for us to link the rich fossil record on land to the global climate signal. Our data shows that integrated temperature differences across the European study area have impacted the extent of IcPD; we will use tie-points from the TL approach and other dating methods to correlate the regional chronologies developed. The primary focus of the first part of the project was on opercula, but for the second part we will continue our expansion to tooth enamel, and to test additional calcite biominerals. As the chronologies develop, we will expand the temporal and spatial range of archaeological sites analysed. This targeted effort will result in a valuable chronology usable across the continent; a completely new type of history with which to test hypotheses about human behaviour. What were the root causes and timings of the evolution and expansion of early humans in Eurasia? Once populations became more established, the rich archaeological record shows apparent differences in tool technologies; but are these a reflection of different species, technical evolution over time, geographical variations in source materials, or cultural tradition? With the EQuaTe timescale, questions like these can finally be tested.