Periodic Reporting for period 3 - EQUATE (Bridging Europe: A Quaternary Timescale For The Expansion And Evolution Of Humans)
Período documentado: 2023-04-01 hasta 2024-09-30
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, 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 time capsules.
Trapped within their crystals (in voids within the crystal, 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. In the laboratory this stored energy 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-occurring biomineral to understand the European archaeological and palaeoclimate record.
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, 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 time capsules.
Trapped within their crystals (in voids within the crystal, 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. In the laboratory this stored energy 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-occurring biomineral to understand the European archaeological and palaeoclimate record.
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.
Over the first 4 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 now have regional IcPD chronologies for France, the Netherlands, 3 regions within Germany, Poland, Hungary, Czechia, Switzerland and Sicily. Analysis of deep sediment core material from the Pannonian Plain and the Heidelberg Basin shows that opercula IcPD’s time range extends to 2.5 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 identify the impact of geothermal heating on IcPD from sediments buried >80 m, enabling long core terrestrial material to be used for amino acid geochronology. We have been able to differentiate earlier parts of an interglacial from later parts, and identify sites where the original chronology was incorrect. We have also shown that novel biominerals (slug plates and worm granules) show age-related IcPD, widening the range of environments able to be dated. We have characterised the protein breakdown of elephant, mammoth, horse, bison & rhino tooth enamel from palaeontological / archaeological sites, showing that taxa is an important factor. Direct dating of these mammalian fossils has enabled us to identify mixed age assemblages, particularly prevalent in cave deposits. Now that we know which taxa to use, we are extending the dating frameworks using tooth enamel.
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 investigated the reproducibility of TL measurements made on opercula, developed new methods for analysing the large and complex datasets obtained, and developed methods of quality control to screen our data. Measurement of the shape and size of opercula, coupled with computer modelling, has allowed us to determine the way that ionizing radiation generates the TL signal, and this will allow us to determine numerical ages based on the TL signal for the first time.
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 investigated the reproducibility of TL measurements made on opercula, developed new methods for analysing the large and complex datasets obtained, and developed methods of quality control to screen our data. Measurement of the shape and size of opercula, coupled with computer modelling, has allowed us to determine the way that ionizing radiation generates the TL signal, and this will allow us to determine numerical ages based on the TL signal for the first time.
There have been four additional breakthroughs so far:
a: The analysis of well-dated material from long sediment cores allowed us to determine the impact of geothermal heating on deeply-buried opercula fossils; this is relevant for material buried >80 m in geothermally warm regions (Nelson et al., 2024), and the impacts are systematic (i.e. will increase with the age of the material dated). This new knowledge allows the Quaternary community to fully exploit long-core samples for amino acid dating.
b: Temperature control of samples during TL measurement is critical, and we have developed a method for accurately monitoring this routinely (Colarossi et al., 2024), and thereby optimised our protocols slowing our heating rate. Automated image analysis methods have been developed to rapidly process TL data and avoid the need for the very expensive sample holders previously required (Duller and Roberts, 2024).
c: Conventional alpha and beta radiation calculations cannot be used as they assume that objects being dated are spherical. New methods for determining the morphology of opercula have been developed, and a new Monte Carlo radiation transport model has allowed us to determine attenuation factors.
d: Testing five different taxa (elephant, mammoth, horse, bison & rhino) has confirmed that there are important taxonomic differences in the way that their enamel protein breaks down (Dickinson et al., 2024). This is critical for IcPD’s application, so now we can target the most useful taxa, developing dating frameworks for each of these commonly-occurring animals.
The data collection so far has provided us with the foundations to link the rich fossil record on land to the global climate signal. Integrated temperature differences across the European study area have impacted the extent of IcPD, and so we will use independently dated tie-points to correlate the regional chronologies. This will result in a chronology usable across the continent with which to test hypotheses about Palaeolithic human behaviour.
a: The analysis of well-dated material from long sediment cores allowed us to determine the impact of geothermal heating on deeply-buried opercula fossils; this is relevant for material buried >80 m in geothermally warm regions (Nelson et al., 2024), and the impacts are systematic (i.e. will increase with the age of the material dated). This new knowledge allows the Quaternary community to fully exploit long-core samples for amino acid dating.
b: Temperature control of samples during TL measurement is critical, and we have developed a method for accurately monitoring this routinely (Colarossi et al., 2024), and thereby optimised our protocols slowing our heating rate. Automated image analysis methods have been developed to rapidly process TL data and avoid the need for the very expensive sample holders previously required (Duller and Roberts, 2024).
c: Conventional alpha and beta radiation calculations cannot be used as they assume that objects being dated are spherical. New methods for determining the morphology of opercula have been developed, and a new Monte Carlo radiation transport model has allowed us to determine attenuation factors.
d: Testing five different taxa (elephant, mammoth, horse, bison & rhino) has confirmed that there are important taxonomic differences in the way that their enamel protein breaks down (Dickinson et al., 2024). This is critical for IcPD’s application, so now we can target the most useful taxa, developing dating frameworks for each of these commonly-occurring animals.
The data collection so far has provided us with the foundations to link the rich fossil record on land to the global climate signal. Integrated temperature differences across the European study area have impacted the extent of IcPD, and so we will use independently dated tie-points to correlate the regional chronologies. This will result in a chronology usable across the continent with which to test hypotheses about Palaeolithic human behaviour.