Stable carbon, oxygen, and nitrogen isotope analysis of serially-sampled fossil tooth enamel from equid third molars from the Eemian site of Neumark-Nord 2, Germany.

Stable carbon (δ13C), nitrogen (δ15N), and oxygen (δ18O) isotopes are well-established proxies for the reconstruction of past diet and environment. δ13C and δ18O can be used to reconstruct the plant-based diets of animals and seasonal environmental patterns. These isotopes are regularly measured in the non-organic component of tooth enamel, which is highly resistant to diagenetic alteration. Likewise, δ15N can be used to reconstruct trophic level and food webs. Up until recently, δ15N could only be measured on relatively young samples (<100,000 years old), because it requires organic material, usually bone collagen or dentin, which rarely preserves in the fossil record. However, in 2021, an oxidation-denitrification method was developed. This method allows for the measurement of the nitrogen isotopic composition of the organic material trapped in the crystalline structure of (fossil) tooth enamel. Thus, we can now measure δ13C, δ15N, and δ18O on the same aliquot of tooth enamel....Show moreStable carbon (δ13C), nitrogen (δ15N), and oxygen (δ18O) isotopes are well-established proxies for the reconstruction of past diet and environment. δ13C and δ18O can be used to reconstruct the plant-based diets of animals and seasonal environmental patterns. These isotopes are regularly measured in the non-organic component of tooth enamel, which is highly resistant to diagenetic alteration. Likewise, δ15N can be used to reconstruct trophic level and food webs. Up until recently, δ15N could only be measured on relatively young samples (<100,000 years old), because it requires organic material, usually bone collagen or dentin, which rarely preserves in the fossil record. However, in 2021, an oxidation-denitrification method was developed. This method allows for the measurement of the nitrogen isotopic composition of the organic material trapped in the crystalline structure of (fossil) tooth enamel. Thus, we can now measure δ13C, δ15N, and δ18O on the same aliquot of tooth enamel. Here, combined δ13C, δ15N, and δ18O isotope data from tooth enamel of 14 serially-sampled fossil equid (Equus sp.) third molars from the ~120,000-year-old Middle Paleolithic Neanderthal site of Neumark-Nord 2, Germany, is presented. Each tooth was sampled along the growth axis and yielded up to 26 sub-samples (total n = 259). Neumark-Nord is a well-preserved archaeological site with a rich vertebrate fauna. It has yielded a large isotopic dataset, which includes some of the oldest stable carbon and nitrogen isotope measurements on bone collagen. This study allows us to expand the isotopic dataset of Neumark-Nord 2 by serially-sampled data, which enables us to reconstruct seasonality for the Last Interglacial (Eemian; MIS 5e/5d transition). δ13C and δ18O of all enamel samples (n = 259) was measured using the cold trap method. Based on these isotope patterns, 72 samples (including all serial measurements of three of the equid teeth) were selected for δ15N measurement, to assess potential seasonal variation in the δ15N values of the enamel. The enamel δ13C, δ15N, and δ18O results are consistent with previously published equid collagen δ13C, δ15N, and bulk enamel δ18O values. A clear seasonal signal is present in the δ18O values of each tooth, with higher values in summer than in winter. This seasonal signal is absent in both the δ13C and δ15N values. This study shows that there is no strong effect of seasonal variation detectable in the δ15N values of nitrogen isotopes in the enamel of equids in temperate environments. This suggests that, in order to measure an accurate average δ15N value, bulk samples of tooth enamel from equids – and likely other large herbivores – in temperature environments do not need to cover an entire year of growth. In addition, the correlation observed between δ13C and δ15N enamel values seems to indicate that, in such environments, the mechanisms controlling carbon and nitrogen isotope fractionation are positively related. Lastly, this study improves the time-resolution of the Neumark-Nord 2 isotopic dataset, allowing for a better reconstruction of the past ecosystem by providing seasonal data.Show less

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Stable carbon, oxygen, and nitrogen isotope analysis of serially-sampled fossil tooth enamel from equid third molars from the Eemian site of Neumark-Nord 2, Germany.