Stable isotope analysis of well-preserved 120,000-year-old herbivore bone collagen from the Middle Palaeolithic site of Neumark-Nord 2, Germany reveals niche separation between bovids and equids

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Abstract

Herbivores from the Neumark-Nord 2 archaeological site, Germany, were analysed for bone collagen stable carbon (δ13C) and nitrogen (δ15N) isotope ratios in order to investigate feeding ecology at this early Last Interglacial (Eemian) shallow-lake site. Of 42 faunal samples selected, 23 yielded collagen, demonstrating remarkable preservation for material of this age. The results indicate clear inter-specific differences in δ15N and δ13C values, notably between equids (Equus) and bovids (Bos/Bison), with mean difference Δ15N of + 2‰ measured in the bovids compared to the equids. The potential reasons for these differences are explored, including physiology, herbivore feeding ecology, biogeography and resource partitioning within the local environment. The data are compared to previously published archaeological data, and modern experimental and ecological data, suggesting that these inter-specific differences are not consistent and therefore unlikely to be solely the product of physiology or habitual forage preference. Data from this study are compared to the local vegetation (as reconstructed from pollen profiles), and it is suggested that these trends are likely the result of niche partitioning at the shallow lake site, reflecting the local diversity in vegetational zones. The evidence for resource partitioning amongst Pleistocene herbivore communities at Neumark-Nord 2 and elsewhere is discussed. This study represents one of the largest data sets for collagen of this age, and the implications for our understanding of Late Pleistocene herbivore ecology, local herbivore community behaviour and hominin palaeodietary studies are explored.

Highlights

► We analysed Eemian herbivore bone collagen (δ13C, δ15N) to infer feeding behaviour. ► Data show inter-specific differences (equids/bovids) suggesting niche separation. ► Cross-site comparisons evidence potential for niche instability through time. ► Niche separation to avoid inter-specific competition and increase biodiversity. ► Importance of total ecosystem approach in hominin palaeodietary studies.

Introduction

The landscapes of Mid- and Late Pleistocene Europe were dominated by large herbivores, including pachyderms (e.g. Mammuthus, Elephas), equids (Equus), cervids (Cervus), and bovids such as bison (Bison) and aurochs (Bos). The mechanisms that allow for the co-existence of different modern mid- and large-sized grazing herbivore guilds have been debated, but are largely thought to lie in their different digestive systems that permit them to adopt alternative foraging strategies where ranges overlap (Janis, 1976), and/or through the selective feeding on different plant communities or portions of plants within the same biome—known as resource partitioning (Krysl et al., 1984, Menard et al., 2002). These mechanisms lead to niche separation, through the occupation of different sub-habitats by the selection of different plants within the same habitat, or different parts of the same plant; and therefore facilitating biodiversity in herbivore species (Janis, 1976). It has previously been suggested that the high diversity of herbivore taxa living in the steppic biomes of Pleistocene North Europe can be explained by such dietary specialisation (Guthrie, 1982), with a proposed high floral biodiversity allowing niche separation and the avoidance of direct inter-specific competition (Drucker et al., 2003). In this study, we investigate the feeding palaeoecology of equids (Equus) and bovids (Bos/Bison) through stable isotope data, and explore the possibility (and nature) of such niche separation in Late Pleistocene Europe. The stable isotope analysis of fossil animal remains is a powerful tool for investigating ancient environments, ecosystems and feeding behaviours, and is a method that can be used to directly investigate differences in herbivore dietary specialisation. Stable isotope techniques are based on the principle that an organism's tissues will reflect the chemical composition of food and water ingested during life (Kohn, 1999). Isotopic methods have been used extensively in recent years to explore the palaeobiology of different species, including predator–prey relationships (Richards et al., 2000, Bocherens, 2003); niche feeding behaviours/resource partitioning (Feranec, 2007, Feranec et al., 2010); and seasonal biogeography and range size (Hoppe et al., 1999, Feranec et al., 2007, Britton et al., 2011). Diachronic and spatial studies allow the assessment of niche conservation and the stability of animal feeding behaviours and biogeography through time (Feranec et al., 2007) and across different geographical regions (Szpak et al., 2010).

In modern case studies, numerous tissues can be used in stable isotope studies, including soft tissues sampled in vivo such as blood, hoof/nail, fur/wool/hair, horn and breath, as well as hard and soft tissues post-mortem such as bone, tooth and muscle. Except in rare cases of good preservation (such as permafrost environments), stable isotope investigations of archaeological and palaeontological materials are normally restricted to skeletal materials, including the inorganic fraction of bone and tooth (so called ‘bioapatite’), and preserved proteins that may be extracted from these mineral matrices such as bone collagen. Collagen is often the favoured analyte for stable isotope studies on archaeological human and animal remains as modern experimental data and published quality control criteria can be used to evaluate extracted ‘collagen’ and assess its integrity prior to data interpretation (Ambrose, 1990, Van Klinken, 1999). Collagen molecules break-down through time in the burial environment, and the processes of diagenesis, hydrolysis and microbial attack can serve to degrade collagen, resulting in its loss or in the alteration of in vivo stable isotope signatures (Ambrose, 1990, Van Klinken, 1999, Collins et al., 2002, Nielsen-Marsh et al., 2007, Smith et al., 2007, Dobberstein et al., 2009). Although the age of deposits can greatly influence the chances of collagen preservation, the rate of protein breakdown largely depends on conditions within the local burial environment (Nielsen-Marsh et al., 2007, Smith et al., 2007) and, where conditions are favourable, well-preserved collagen can be extracted and analysed from Late Pleistocene samples dating to older than 50,000 yr BP (Fizet et al., 1995, Bocherens et al., 1997, Bocherens et al., 1999, Bocherens et al., 2001, Jones et al., 2001).

Here, we report the results of stable carbon (δ13C) and nitrogen (δ15N) isotope analysis of herbivore bone collagen from the site of Neumark-Nord 2, Germany (archaeological find layer NN2/2), with the aim of investigating potential differences in herbivore feeding ecology at this early Last Interglacial (Eemian) ‘water-hole’ site. Carbon and nitrogen composition and mass ratios of ultra filtered bone collagen show that the samples are mostly well preserved, indicating extracted proteins are useful for reconstructing diet and feeding ecology. The data are explored for inter-specific differences and compared to previously published bone collagen isotope data from a range of other Late Pleistocene sites. Issues of herbivore digestive physiology, niche separation and resource partitioning amongst Late Pleistocene equids and bovids are discussed, and the implications for hominin palaeodietary studies are addressed.

Section snippets

Reconstructing herbivore ecology using carbon and nitrogen isotope analysis

Carbon and nitrogen stable isotope techniques are based around the principle that animal body tissues (e.g. bulk bone collagen) reflect the isotopic composition of the food ingested throughout life. The relative abundance of the stable isotopes of carbon, 13C and 12C (δ13C), varies characteristically between different biological communities e.g. between plants of different photosynthetic pathway (Smith and Epstein, 1970, Deniro and Epstein, 1978) or between terrestrial and marine ecosystems (

The site of Neumark-Nord 2

The site of Neumark-Nord 2 is located approximately 35 km west of Leipzig in Saxony-Anhalt, Germany (51°19′28″N, 11°53′56″E). First discovered in the 1980s, this area of the Geisel Valley contains a series of shallow Middle and Late Pleistocene basins, rich with faunal remains and Palaeolithic artefacts (Strahl et al., 2010, Sier et al., 2011). The basins, formed by isostatic movements induced by lignite diapirism (Eissman, 2002, Mania and Mania, 2008), include the proximal sites of Neumark-Nord

Methods

In this study, collagen was successfully extracted and analysed from 232 samples (Bos/Bison, n = 15; Equus sp., n = 7; cervid, n =

Results

Isotopic results from the animal bone collagen extracted and analysed from Neumark-Nord 2 are given in Table 1 (n = 23). The C:N ratio, %C, %N and collagen yield for all samples are also presented. In each instance, it is indicated whether data was obtained from the smaller (10–30 kDa) or larger (> 30 kDa) ultrafilter fraction. The atomic C:N ratios of the samples analysed ranges between the range of 3.1 and 3.5, and are therefore within the expected range for well-preserved bone (Deniro, 1985,

Quality and preservation of organic material

The C:N ratios, %C and %N data of the majority of the samples indicate good collagen preservation. Thus, we can consider the samples to carry reliable isotopic signatures and therefore these can be used to elucidate palaeoenvironmental, palaeoecological and palaeodietary information. Given the age of these samples, this preservation is remarkable. Such preservation is considered rare, and there are very few other published examples of isotope studies on collagen of comparable age or older which

Conclusions

This study represents one of the largest bone collagen stable isotope data sets from an early Last Interglacial (Eemian) site, likely due to the favourable local preservation conditions at Neumark-Nord 2. Carbon and nitrogen isotope analysis of extracted herbivore bone collagen revealed inter-specific differences in δ15N and δ13C between equids, bovids and a single cervid at the site and the potential explanations for these differences have been explored, including physiology, herbivore feeding

Acknowledgements

With thanks to Stefanie Bösel, Annabell Reiner and Olaf Nehlich (MPI-EVA) for technical and practical support with isotope analysis; and to the Landesamt für Denkmalpflege und Archäologie, Saxony-Anhalt, and Landesmuseum Sachsen-Anhalt in Halle for providing samples; to Olaf Nehlich and Sandi Copeland (MPI-EVA, UC-Boulder) for comments on early versions of this manuscript; to Corrie Bakels (Leiden) for her perspectives on the pollen record at Neumark-Nord 2; and to Jane Degabriel (Aberdeen) for

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    Current address: Department of Archaeology, University of Aberdeen, St. Mary's Building, Elphinstone Road, Aberdeen, AB24 3UF, UK.

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