Browsing by Subject "RATIOS"

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  • Oinonen, Markku; Alenius, Teija; Arppe, Laura; Bocherens, Hervé; Etu-Sihvola, Heli; Helama, Samuli; Huhtamaa, Heli; Lahtinen, Maria; Mannermaa, Kristiina; Onkamo, Päivi; Palo, Jukka; Sajantila, Antti; Salo, Kati; Sundell, Tarja; Vanhanen, Santeri; Wessman, Anna (2020)
    Levanluhta is a unique archaeological site with the remains of nearly a hundred Iron Age individuals found from a water burial in Ostrobothnia, Finland. The strongest climatic downturn of the Common Era, resembling the great Fimbulvinter in Norse mythology, hit these people during the 6th century AD. This study establishes chronological, dietary, and livelihood synthesis on this population based on stable carbon and nitrogen isotopic and radiocarbon analyses on human remains, supported by multidisciplinary evidence. Extraordinarily broad stable isotopic distribution is observed, indicating three subgroups with distinct dietary habits spanning four centuries. This emphasizes the versatile livelihoods practiced at this boundary of marine, freshwater, and terrestrial ecosystems. While the impact of the prolonged cold darkness of the 6th century was devastating for European communities relying on cultivation, the broad range of livelihoods provided resilience for the Levanluhta people to overcome the abrupt climatic decline.
  • Watzinger, Andrea; Schott, Katharina; Hood-Nowotny, Rebecca; Tamburini, Federica; Arppe, Laura; Cristini, Domiziana; Knoeller, Kay; Skrzypek, Grzegorz (2021)
    Rationale A silver phosphate reference material (Ag3PO4) for the measurement of stable oxygen isotope compositions is much needed; however, it is not available from the authorities distributing reference materials. This study aims to fill this gap by calibrating a new Ag3PO4 stable isotope comparison material produced by the University of Natural Resources and Life Sciences (BOKU). Methods Aliquots of Ag3PO4 were distributed to four laboratories who frequently measure the delta O-18 value in Ag3PO4; the University of Natural Resources and Life Sciences (BOKU), the University of Western Australia (UWA), the University of Helsinki (UH), and the Helmholtz Centre for Environmental Research (UFZ). The instruments used to perform the measurements were high-temperature conversion elemental analysers coupled with continuous flow isotope ratio mass spectrometers. The working gas delta O-18 value was set to 0 parts per thousand and the normalization was done by a three-point linear regression using the reference materials IAEA-601, IAEA-602, and NBS127. Results The mean delta O-18 value of the new BOKU Ag3PO4 comparison material on the VSMOW-SLAP scale is 13.71 parts per thousand and the combined uncertainty is estimated as +/- 0.34 parts per thousand. This estimated uncertainty is within the range typical for comparison materials of phosphates and sulphates. Consistent results from the different laboratories probably derived from similar instrumentation, and use of the same reference materials and normalization procedure. The matrix effect of the different reference materials used in this study was deemed negligible. Conclusions The BOKU Ag3PO4 can be used as an alternative comparison material for stable oxygen isotope analysis and is available for stable isotope research laboratories to facilitate calibration.
  • Rautiala, Petri; Helantera, Heikki; Puurtinen, Mikael (2018)
    In haplodiploids, females can produce sons from unfertilized eggs without mating. However, virgin reproduction is usually considered to be a result of a failure to mate, rather than an adaptation. Here, we build an analytical model for evolution of virgin reproduction, sex-allocation, and altruistic female helping in haplodiploid taxa. We show that when mating is costly (e.g., when mating increases predation risk), virginity can evolve as an adaptive female reproductive strategy. Furthermore, adaptive virginity results in strongly divergent sex-ratios in mated and virgin queen nests ("split sex ratios"), which promotes the evolution of altruistic helping by daughters in mated queen nests. However, when helpers evolve to be efficient and increase nest production significantly, virgin reproduction is selected against. Our results suggest that adaptive virginity could have been an important stepping stone on the pathway to eusociality in haplodiploids. We further show that virginity can be an adaptive reproductive strategy also in primitively social haplodiploids if workers bias the sex ratio toward females. By remaining virgin, queens are free to produce sons, the more valuable sex in a female-biased population. Our work brings a new dimension to the studies linking reproductive strategies with social evolution.