F Rosa Rubicondior: Creationism in Crisis - Sudden Climate Change Recorded In Marine Mollusc Shells - From 8,400 Years Before Creationism's Global Genocide

Wednesday 6 March 2024

Creationism in Crisis - Sudden Climate Change Recorded In Marine Mollusc Shells - From 8,400 Years Before Creationism's Global Genocide

Marine mollusc shells reveal how prehistoric humans adapted to intense climate change - Universitat Autònoma de Barcelona - UAB Barcelona
In an event known to geologists as the '8.2 Ka event', i.e. 8.2 Kilo anum (thousand years) event, a sudden flow of cold water melt-water from the North American lakes into the North Atlantic stopped the 'Atlantic Conveyer' from bringing warm water from the Gulf of Mexico up to the coast of Western Europe and with it warm, moist air. This even significantly and quite suddenly changed the climate to a colder, drier weather pattern which affected marine wildlife.

That event was subsequently recorded in the shells of the marine molluscs the people living along the Cantabrian Coast of Northern Spain gathered for food, disposing of the shells in midden tips, such as in the El Mazo cave in Asturias, Spain. The 8.2 Ka event also had a profound effect on the human societies as their food disappeared or migrated to more equitable areas.

If the creationists story of a global genocidal flood were true, then this record would have been swept away and destroyed, or at least buried under the predicted layer of silt and dead animal and plant remains that such a flood would have made inevitable. But there it is, looking for all the world like there never was a global flood and not so much as a centimeter of silt covering it.

The midden in the El Mazo cave was in use for about 1500 years, producing a continuous stratigraphic record with a very high chronological resolution, which is now the subject of a paper in Scientific Reports by a team of archaeologists led by Asier García Escárzaga, current researcher from the Institute of Environmental Science and Technology (ICTA-UAB) and the Department of Prehistory of the Universitat Autònoma de Barcelona, together with Igor Gutiérrez Zugasti, from the Universidad de Cantabria (UC). The study was coordinated from the Universidad de La Rioja (UR) and the Max Planck Institute (Germany) alongside members of other academic centres (Max Planck Institute, University of Burgos, Universidad Complutense de Madrid and University of Faro).

The study applies a multidisciplinary toolkit of archaeomalacological studies and stable oxygen isotope analyses to shell remains recovered from the shell midden site.
How does measuring the δ18O levels in marine mollusc shells tell archaeologists about the water temperature? Measuring the δ18O (delta-18O) levels in marine mollusc shells can provide valuable insights into past water temperatures. Here's how it works:
  1. Isotopic Composition: Oxygen comes in different isotopes, primarily 16O and 18O. The ratio of these isotopes (δ18O) in water varies depending on factors like temperature and the source of the water.
  2. Incorporation into Shells: Marine molluscs incorporate the oxygen from seawater into their shells when they build them. The isotopic composition of the oxygen in the shell reflects the composition of the seawater at the time the shell was formed.
  3. Temperature Dependency: The ratio of 18O to 16O in seawater is influenced by temperature. Generally, colder water tends to have a higher proportion of 18O compared to 16O. This is because 18O is slightly heavier and less likely to evaporate or be incorporated into ice, so it's enriched in colder water.
  4. Proxy for Past Temperatures: By analyzing the δ18O values in mollusc shells, scientists can infer the temperature of the seawater when the shell was formed. Higher δ18O values suggest warmer water temperatures, while lower values indicate colder temperatures.
  5. Calibration and Interpretation: To use δ18O values as a proxy for temperature, scientists often need to calibrate the relationship between δ18O and temperature using modern samples. Once calibrated, they can apply this relationship to ancient shell samples to estimate past temperatures.
  6. Additional Considerations: It's essential to consider factors other than temperature that can influence δ18O values, such as salinity and changes in the isotopic composition of seawater over time. However, with careful calibration and consideration of these factors, δ18O analysis in mollusc shells can provide valuable information about past ocean temperatures, aiding archaeologists and paleoclimatologists in reconstructing past environments and climates.
From the Universitat Autònoma de Barcelona (UAB) press release:
The results obtained by these scientists allowed them to determine that colder seawater temperatures, deduced from stable oxygen isotope values measured on marine shells, led to changes in the availability of different shellfish species. For instance, one of the most commonly consumed species, the warm-adapted species P. lineatus, decreased during the 8.2 ka event, while populations of cold-adapted P. vulgata, another commonly exploited species, increased. Intriguingly, the warm-adapted limpet P. depressa also increased during this cool period, owing to a higher resistance to cold temperatures than other warm-water species.

Their results also revealed an increase in the intensification of mollusc exploitation by humans, as indicated by a decrease in average mollusc size and evidence for increased harvesting in more dangerous coastal areas. The authors argued that this occurred because of human demographic growth in these Atlantic coastal settings which acted as refugia during this cold event, encouraging populations to move there from further inland. Nevertheless, populations around El Mazo managed to avoid over exploiting their coastal resources, as average mollusc size very rarely decreased below 20mm, the minimum size specified by modern regulations to guarantee long-term species survival.

“Our results suggest an ongoing application of local marine ecological knowledge by some of the last foragers in western Europe, despite major changes to climate and demography” says Asier García-Escárzaga lead author of the current study.

The resolution provided by the combination of taxonomic, geochemical and chronological analysis of molluscs from archaeological sites has major implications for other studies seeking to determine the significance of climate change on marine environments, and can provide detailed clues to the magnitude and nature of future climate changes and their impacts on human societies.
In their published paper the team say:
The cooling and drying associated with the so-called ‘8.2 ka event’ have long been hypothesized as having sweeping implications for human societies in the Early Holocene, including some of the last Mesolithic hunter-gatherers in Atlantic Europe. Nevertheless, detailed ‘on-site’ records with which the impacts of broader climate changes on human-relevant environments can be explored have been lacking. Here, we reconstruct sea surface temperatures (SST) from 18O values measured on subfossil topshells Phorcus lineatus exploited by the Mesolithic human groups that lived at El Mazo cave (N Spain) between 9 and 7.4 ka. Bayesian modelling of 65 radiocarbon dates, in combination with this 18O data, provide a high-resolution seasonal record of SST, revealing that colder SST during the 8.2 ka event led to changes in the availability of different shellfish species. Intensification in the exploitation of molluscs by humans indicates demographic growth in these Atlantic coastal settings which acted as refugia during this cold event.


Current global climate warming is having, and will continue to have, widespread consequences for humans. Looking to the past, multiple climatic and environmental changes have long been thought to have shaped human evolution and behaviour1,2,3. The Holocene (11.7–0 ka cal BP) is a geological epoch characterized by comparative stable climatic conditions. However, that stability was punctuated by a series of sudden climate changes, particularly during the Early Holocene4. Among these, the ‘8.2 ka event’ has been identified as the largest and most abrupt climatic event of the Holocene5,6. Climate scientists suggest that this ‘event’ was the result of an outburst of glacial meltwater from the Laurentide lakes in North America7. The influx of cold water into the Atlantic Ocean led to a reduction of sea surface salinity and a decline of the Atlantic meridional overturning circulation (AMOC), provoking a reduction in sea surface temperatures (SST) across the North Atlantic8. The cooling effects of this event have been documented in proxies from the Greenland ice cores6 and across Europe5,9,10. Short and sharp periods of colder or drier conditions have also been recorded ~ 8.2 ka throughout the northern11,12,13 and southern hemispheres11,12,14. Nevertheless, while now a well-established climatic phenomenon, the sweeping impacts of the ‘8.2 ka event’ on different environments often remain assumed rather than proven, and local records of marine or terrestrial conditions available at an appropriate resolution often remain lacking. Furthermore, while temperature or rainfall changes associated with the ‘8.2 ka event’ are often well-established, there are few palaeoclimatic proxies available that have enabled insights into the influence of the ‘8.2 ka event’ on the seasonality of climatic conditions in different parts of the world.

These gaps relating to the impact of this cold event on local environments are problematic given that there have been a number of attempts to link the ‘8.2 ka event’ to changes in past human societies, with cooling and drying being argued to have stimulated behavioural or settlement responses15,16. In the Middle East, a 300-year period of drying and cooling has been associated with economic and cultural changes leading to an increase in social stratification and urbanism in the region17. Aridity at ~ 8.2 ka has also been correlated with changes in settlement patterns and human subsistence in North and East Africa18. On the Atlantic façade of Europe, the ‘8.2 ka event’ occurred at a time when some of the last Mesolithic hunter-gatherers in Europe were producing dense shell middens along the coast prior to the arrival of agriculture19. Given the apparent reliance of human societies on marine resources, it has been hypothesised that this abrupt climate change must have affected the availability of exploited marine taxa and thus the foraging behaviours, settlement patterns, and spatial mobility of prehistoric human populations20. However, as with previous examples, high-resolution local palaeoclimatic records that are directly associated with areas of human occupation have remained generally lacking16. Moreover, given the known importance of seasonal patterns in subsistence strategies to hunter-gatherers21,22, seasonal records of changes in marine and terrestrial conditions are particularly important. Nonetheless, suitable proxies and precise sequence chronologies have remained scarce.

Marine molluscs have very specific environmental requirements and are extremely sensitive to climate change, as revealed by previous studies across Atlantic Europe23,24. Recent research has demonstrated that the current rising of SST is forcing a rapid expansion of the northern limit of warm-adapted marine species24,25. Similarly, warmer conditions during the Early Holocene have been argued to have led to significant changes in species representation when compared to Pleistocene glacial conditions26. Mollusc species recovered from archaeological deposits thus have high potential to provide temperature information of direct significance to humans occupying particular sites and exploiting marine resources27. Recent developments in the radiocarbon dating of shell carbonate have improved our understanding of the dating of this material, allowing researchers to accurately determine the chronology of climate change decoded from shell remains28. Beyond taxonomic indications, stable oxygen isotope ratios derived from archaeologically-recovered marine mollusc shells (18Oshell) have been demonstrated to be powerful recorders of the seasonal SST variations experienced by that animal in the past29,30, offering unparalleled insights into the seasonality of marine environments relied upon by past human populations. Significantly, the effectiveness of these seasonal palaeothermometers has also been demonstrated on the European Atlantic façade for Phorcus lineatus (da Costa, 1778)21,31,32, a topshell species that comprises a significant proportion of Mesolithic shell middens found in the region. The difficult task, until now, however, has been to find a shell midden with sufficient temporal resolution to enable inference of short and abrupt changes in climate conditions and human behaviour19.

Here, we report chronological, archaeomalacological and isotopic data from shellfish remains recovered from the site of El Mazo in northern Spain (Fig. 1; Supplementary Text 1; Supplementary Fig. 1). We performed a large number of radiocarbon measurements on different materials, including bone from terrestrial animals, microbotanical remains, and marine mollusc shells to generate a high-resolution chronological sequence of the human use of the cave. Meanwhile, measurements of 18Oshell on subfossil topshells P. lineatus were used to accurately reconstruct short-term changes in coastal SST throughout the Early Holocene. In addition, distributions of shell assemblages were quantified to determine marine mollusc species representation, diachronic changes in shell size, harvesting areas, and the occurrence of shell size selection by humans. Significantly, the site is unique in the context of the European Atlantic façade given its long stratigraphic sequence (9–7.4 ka cal BP), but especially, the high chronological resolution of each unit. As a result, it offers an important opportunity to decipher, for the first time, the duration and the seasonal impact of the 8.2 ka event on SST in Atlantic Europe, its impacts on littoral resources that were being heavily exploited by humans, and its broader ramifications for the settlement patterns and economies of some of the last dedicated hunter-gatherer groups in Europe prior to the expansion of domesticated plants and animals into the region. The study of ‘on-site’ palaeoenvironmental indicators, at a seasonal resolution, also demonstrates the significant potential of this methodology, which can be applied to multiple sites, to explore the overall, and intra-annual, effects of abrupt climate changes on specific environments where the resolution of archaeological sites allows.
Figure 1
(a) Location of the study area (Cantabrian region, northern Spain) and the shell midden site of El Mazo. (b) External view of El Mazo; (c) topographic map of the site showing excavation areas and provenance of the studied samples (shaded squares), and (d) stratigraphy of the inner test pit (squares X15 and X16). Satellite map in the upper-left corner of (a) was created by authors using Adobe® Illustrator software. The original base map was extracted from the maps-for-free web site (https://maps-for-free.com/) (© Collaborators of OpenStreetMap, Open Database License [ODbL]). Map in the upper-right corner of (a) was generated by Alejandro Garcia-Moreno using ArcGIS software. Lower map of (a) was created by Luis C. Teira Mayolini using ArcGIS and Adobe Suite software.
García-Escárzaga, A., Gutiérrez-Zugasti, I., Marín-Arroyo, A.B. et al.
Human forager response to abrupt climate change at 8.2 ka on the Atlantic coast of Europe.
Sci Rep 12, 6481 (2022). https://doi.org/10.1038/s41598-022-10135-w

Copyright: © 2024 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
So, in addition to the lack of any evidence of a global flood, we also have this 1,500 year record, in the form of a midden, of continuous habitation through the 8.2 Ka event, which takes it back to just 300 years after creationists claim the Universe was created, during which time we are expected to believe, humans migrated from the Middle East and established hunter-gatherer communities along the coast of Northn Spain, then, to cap it all, their midden tip miraculously survived a cataclysmic global flood and never had so much as a teaspoon full of the silt over it that such a flood would have produced, even if it hadn't washed the shells away.

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