| 1. |
- Kirillova, Irina V., et al.
(författare)
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'Semi-dwarf' woolly mammoths from the East Siberian Sea coast, continental Russia
- 2020
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 49:2, s. 269-285
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Tidskriftsartikel (refereegranskat)abstract
- A pioneer comprehensive study of several diminutive last-generation woolly mammoth teeth (M3) found on the coast of the East Siberian Sea between the mouths of the Alazeya and Malaya Kuropatoch'ya rivers was conducted. Two teeth belonged to one individual. These teeth have a similar lamellar frequency and enamel thickness as teeth of Mammuthus primigenius Blumenbach. The molar crowns from the lower Alazeya region are similar in size to those of the small Late Pleistocene-Holocene mammoths from Wrangel Island. However, the number of plates (17-19, excluding talons) is much lower than that in the teeth of typical Late Pleistocene M. primigenius (23-25). The age data of the examined teeth are beyond the limits of the C-14 dating method (>45 000 years BP). Nevertheless, palaeobotanical data allow correlation of the enclosing sediments with the warm Kazantsevo Interglacial (Eemian, MIS 5e) and reconstruction of the average annual temperature, which was warmer than present-day temperatures. These conditions are confirmed by the delta O-18 isotopes from the structurally bound carbonate in tooth enamel. The ancient landscape was wetter and more forested than modern landscapes. The diminution of M3 size and loss of posterior plates were a result of the overall decrease in body size, likely in response to landscape change and narrowing of resource space. Mammoths from the lower Alazeya region demonstrate a stage of significant size reduction, although the dwarfing was not finalized. Their teeth are the oldest amongst the small teeth found in west Beringia.
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| 4. |
- Blaauw, Maarten, et al.
(författare)
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A Bayesian framework for age-modelling of radiocarbon-dated peat deposits: case studies from the Netherlands
- 2007
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Ingår i: Radiocarbon. - 0033-8222 .- 1945-5755. ; 49:2, s. 357-367
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Tidskriftsartikel (refereegranskat)abstract
- Recently, Bayesian statistical software has been developed for age-depth modeling (“wiggle-match dating”) ofsequences of densely spaced radiocarbon dates from peat cores. The method is described in non-statistical terms, and is com-pared with an alternative method of chronological ordering of 14C dates. Case studies include the dating of the start of agri-culture in the northeastern part of the Netherlands, and of a possible Hekla-3 tephra layer in the same country. We discussfuture enhancements in Bayesian age modeling.
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| 5. |
- Blaauw, Maarten, et al.
(författare)
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Testing the timing of radiocarbon-dated events between proxy archives
- 2007
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 17:2, s. 283-288
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Tidskriftsartikel (refereegranskat)abstract
- For interpreting past changes on a regional or global scale, the timings of proxy-inferred events are usually aligned with data from other locations. However, too often chronological uncertainties are ignored in proxy diagrams and multisite comparisons, making it possible for researchers to fall into the trap of sucking separate events into one illusionary event (or vice versa). Here we largely solve this ‘suck in and smear syndrome’ for radiocarbon (14C) dated sequences. In a Bayesian framework, millions of plausible age-models are constructed to quantify the chronological uncertainties within and between proxy archives. We test the technique on replicated high-resolution 14C-dated peat cores deposited during the ‘Little Ice Age’ (c. AD 1400-1900), a period characterized by abrupt climate changes and severe 14C calibration problems. Owing to internal variability in proxy data and uncertainties in age-models, these (and possibly many more) archives are not consistent in recording decadal climate change. Through explicit statistical tests of palaeoenvironmental hypotheses, we can move forward to systematic interpretations of proxy data. However, chronological uncertainties of non-annually resolved palaeoclimate records are too large for answering decadal timescale questions.
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| 6. |
- Blockley, Simon, et al.
(författare)
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Building and testing age models for radiocarbon dates in Lateglacial and Early Holocene sediments
- 2007
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 26:15-16, s. 1915-1926
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Tidskriftsartikel (refereegranskat)abstract
- The growing importance of understanding past abrupt climate variability at a regional and global scale has led to the realisation that independent chronologies of past environmental change need to be compared between various archives. This has in turn led to attempts at significant improvements in the required precision at which records can be dated. Radiocarbon dating is still the most prominent method for dating organic material from terrestrial and marine archives, and as such many of the recent developments in improving precision have been aimed at this technique. These include: (1) selection of the most suitable datable fractions within a record, (2) the development of better calibration curves, and (3) more precise age modelling techniques. While much attention has been focussed on the first two items, testing the possibilities of the relatively new age modelling approaches has not received much attention. Here, we test the potential for methods designed to significantly improve precision in radiocarbon-based age models, wiggle match dating and various forms of Bayesian analyses. We demonstrate that while all of the methods can perform very well, in some scenarios, caution must be taken when applying them. It appears that an integrated approach is required in real life dating situations where more than one model is applied, with strict error calculation, and with the integration of radiocarbon data with sedimentological analyses of site formation processes.
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| 8. |
- Dury, Jack, 1993-
(författare)
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Dealing With Reservoir Effects in Human and Faunal Skeletal Remains : Understanding the radiocarbon dating of aquatic samples
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Archaeology relies on the ordering of past events to study cultural developments. This has traditionally been achieved by looking at the stratigraphic depths of materials relative to one another. In this way, chronologies of past technological progressions and stylistic changes can be built. The introduction of radiocarbon dating in the 1950s revolutionised archaeology, allowing for direct, numerical estimates of a sample’s age. This allowed for more detailed past chronologies than was previously possible. Radiocarbon dating utilises the radioactive decay of carbon-14 (radiocarbon, 14C) to estimate a sample’s age with older samples having less 14C. Shortly after the introduction of radiocarbon dating, however, it was demonstrated that 14C is not evenly distributed globally. Typically, there is less 14C in marine (and sometimes freshwater) systems compared to the atmosphere. This results in aquatic samples appearing older than they are, a phenomenon known as a ‘reservoir effect’. When radiocarbon dating material from archaeological sites with marine activity, this is an important consideration. With aquatic resources being vital for human populations across the globe and for millennia, the ability to interpret aquatic radiocarbon dates is incredibly important. Making use of radiocarbon dates without properly handling any reservoir effects have proved problematic, sometimes resulting in archaeologically incorrect chronologies being constructed. Reservoir effects can, however, be managed. This thesis demonstrates how archaeologists should interpret radiocarbon dates from aquatic samples, avoiding erroneously-old age estimates. Through careful sample selection, considering complicated carbon source mixing, measuring the scale and variability of reservoir effects within a single ecosystem and using prior knowledge about a sample’s age, the dating of aquatic material can be greatly improved. This thesis also details a novel method of dating teeth, reducing uncertainty, and concomitantly estimating the extent of the reservoir effect. This was achieved by dating dental increments, combined with complex modelling. It is clear that there is no single method of handling reservoir effects, and methods for dealing with reservoir effects will differ depending on the archaeological site and specific research question. In this thesis, novel and existing methods of dealing with reservoir effects are demonstrated by considering five case studies from four archaeological sites:At the site of Hamanaka 2 (Rebun Island, Japan), it is demonstrated that by carefully selecting samples without reservoir effects, the dating of the stratigraphy of the site can be accurately modelled. Concerning the cemetery site of Rounala (northern Sweden), it is demonstrated that by carefully reconstructing complex human diets, the dating of humans can be modelled to a high resolution. This has implications for the understanding of the Church’s relationship with the cemetery. At the site of Ekven (Chukotka, Bering Strait) reservoir effect variability between species is carefully described. A more detailed understanding of regional reservoir effects allows for more accurate dating of human remains from the marine hunting Old Bering Sea culture. More accurate dating of human remains allows for the refining of existing Old Bering Sea culture chronologies. Finally, concerning the material from Resmo (Ӧland, Sweden), a novel dental wiggle matching model is presented as a possible method for reducing dating uncertainty in individuals with a marine dietary component.
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| 9. |
- Dury, Jack, et al.
(författare)
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Species-specific reservoir effect estimates : A case study of archaeological marine samples from the Bering Strait
- 2022
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 32:11, s. 1209-1221
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Tidskriftsartikel (refereegranskat)abstract
- Due to the marine reservoir effect, radiocarbon dates of marine samples require a correction. Marine reservoir effects, however, may vary among different marine species within a given body of water. Factors such as diet, feeding depth and migratory behaviour all affect the 14C date of a marine organism. Moreover, there is often significant variation within single marine species. Whilst the careful consideration of the ΔR values of a single marine species in a given location is important, so too is the full range of ΔR values within an ecosystem. This paper illustrates this point, using a sample pairing method to estimate the reservoir effects in 17 marine samples, of eight different species, from the archaeological site of Ekven (Eastern Chukotka, Siberia). An OxCal model is used to assess the strength of these estimates. The marine reservoir effects of samples passing the model range from ΔR (Marine20) = 136 ± 41–ΔR = 460 ± 40. Marine reservoir effect estimates of these samples and other published samples are used to explore variability in the wider Bering Strait region. The archaeological implications of this variability are also discussed. The calibrating of 14C dates from human bone collagen, for example, could be improved by applying a dietary relevant marine reservoir effect correction. For humans from the site of Ekven, a ΔR (Marine20) correction of 289 ± 124 years or reservoir age correction of 842 ± 123 years is suggested.
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| 10. |
- Lord, Edana, et al.
(författare)
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Pre-extinction Demographic Stability and Genomic Signatures of Adaptation in the Woolly Rhinoceros
- 2020
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 30:19
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Tidskriftsartikel (refereegranskat)abstract
- Ancient DNA has significantly improved our understanding of the evolution and population history of extinct megafauna. However, few studies have used complete ancient genomes to examine species responses to climate change prior to extinction. The woolly rhinoceros (Coelodonta antiquitatis) was a cold-adapted megaherbivore widely distributed across northern Eurasia during the Late Pleistocene and became extinct approximately 14 thousand years before present (ka BP). While humans and climate change have been proposed as potential causes of extinction [1-3], knowledge is limited on how the woolly rhinoceros was impacted by human arrival and climatic fluctuations [2]. Here, we use one complete nuclear genome and 14 mitogenomes to investigate the demographic history of woolly rhinoceros leading up to its extinction. Unlike other northern megafauna, the effective population size of woolly rhinoceros likely increased at 29.7 ka BP and subsequently remained stable until close to the species’ extinction. Analysis of the nuclear genome from a similar to 18.5-ka-old specimen did not indicate any increased inbreeding or reduced genetic diversity, suggesting that the population size remained steady for more than 13 ka following the arrival of humans [4]. The population contraction leading to extinction of the woolly rhinoceros may have thus been sudden and mostly driven by rapid warming in the Bolling-Allerod interstadial. Furthermore, we identify woolly rhinoceros-specific adaptations to arctic climate, similar to those of the woolly mammoth. This study highlights how species respond differently to climatic fluctuations and further illustrates the potential of palaeogenomics to study the evolutionary history of extinct species.
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