PNAS | May 22, 2001 | vol. 98 | no. 11 | 6528-6532
Stable isotope evidence for increasing dietary breadth in the European mid-Upper Paleolithic
Michael P. Richards, Paul B. Pettitt,, Mary C. Stiner, and Erik Trinkaus,
Department of Archaeological Science, University of Bradford, Bradford, West Yorkshire, BD7 1DP, United Kingdom; Research Laboratory for Archaeology and the History of Art, University of Oxford, 6 Keble Road, Oxford OX1 3QJ, United Kingdom; Keble College, Oxford OX1 3PG, United Kingdom; § Department of Anthropology, University of Arizona, Tucson, AZ 85721; and Department of Anthropology, Washington University, Campus Box 1114, St. Louis, MO 63130
Contributed by Erik Trinkaus, March 28, 2001
Abstract
New carbon and nitrogen stable isotope values for human remains dating to the mid-Upper Paleolithic in Europe indicate significant amounts of aquatic (fish, mollusks, and/or birds) foods in some of their diets. Most of this evidence points to exploitation of inland freshwater aquatic resources in particular. By contrast, European Neandertal collagen carbon and nitrogen stable isotope values do not indicate significant use of inland aquatic foods but instead show that they obtained the majority of their protein from terrestrial herbivores. In agreement with recent zooarcheological analyses, the isotope results indicate shifts toward a more broad-spectrum subsistence economy in inland Europe by the mid-Upper Paleolithic period, probably associated with significant population increases.
Introduction
Human subsistence patterns during the Late Pleistocene have been inferred principally from faunal remains preserved in archeological sites; from the uses of stone tools based on form, microwear traces, and organic residue analysis; and occasionally from preserved vegetal remains. Although it is recognized generally that Late Pleistocene human diets must have included a variety of plants and animals, the majority of the studies conducted to date have focused on large mammal remains and taphonomic arguments about the changing nature of human exploitation of those animals. By the late Upper Paleolithic period (during oxygen isotope stage 2), however, paleontological, paleobotanical, and technological evidence all indicate substantial broadening of human diets in several regions of the Old World. For the earlier phases of the Upper Paleolithic and the Middle Paleolithic, zooarcheological data relating to the exploitation of resources other than large-bodied terrestrial vertebrates are more geographically variable and rare, but gradually emerging (1, 2). One less-documented family of resources consumed by Late Pleistocene humans before the Last Glacial Maximum [18-20 ka (thousand years) before present (BP)] is animals from aquatic habitats (but see refs. 3-5).
It is possible to assess the relative proportion of aquatic resources in the diets of prehistoric foragers and coextant animals through analyses of bone collagen carbon (13C) and nitrogen (15N) stable isotope values. These data provide direct information about average dietary protein intake by prehistoric consumers over an approximately 10-year period before their deaths (6, 7). Although generally silent on the exact range of prey species involved, the isotope data can reflect the proportionality or relative importance of certain kinds of foodstuffs obtained from distinct habitats such as freshwater wetlands, sea coasts, and dry terrestrial landscapes.
To compare the relative roles of aquatic resources in European early modern and late archaic human populations, we analyzed the 13C and 15N values of collagen extracted from nine modern human skeletons dating to the mid-Upper Paleolithic period in Europe and west-central Asia. These data are combined with published results (8-10) on five late archaic humans (Neandertals) from the western portion of the same general geographic region. The latitudinal distribution of the samples is 45°N to 60°N, and most of the samples come from inland regions. A critical distinction is made in this study between marine and freshwater animal resources. Marine exploitation is documented from zooarcheological evidence as early as the Middle Paleolithic of the Last Interglacial (oxygen isotope stage 5e) some 110 ka BP (4), but the scale of exploitation seems to increase with time. Exploitation of fish and other animals from freshwater habitats is a rather different story, because zooarcheological evidence for this behavior does not emerge until much later, and it is most abundant in the zooarcheological record after the Last Glacial Maximum (about 20 ka BP; e.g., refs. 11-13). Freshwater aquatic resources potentially include fish, certain large-bodied mollusks, and the many waterfowl species that feed on aquatic plants, invertebrates, and small vertebrates (e.g., rails and ducks).
Given that there are few reliably dated modern human remains from the early Upper Paleolithic (36-29 ka BP, i.e., the Aurignacian), we have focused on samples from the subsequent mid-Upper Paleolithic (28-20 ka BP), including phases variously termed the Upper Perigordian, Gravettian, Pavlovian, and Streletskayan (14). The sample includes specimens from Brno-Francouzská and Dolní Vstonice (Czech Republic), Kostenki, Mal'ta and Sunghir (Russia), and Paviland (Great Britain). All have been dated directly by the accelerator mass spectrometry radiocarbon technique and, with the exception of Kostenki 1, their uncalibrated ages fall between 26-20 ka BP (Table 3). We contrast these data with published 13C and 15N values for five Neandertals from inland Europe that date to roughly 130-28 ka BP (Table 4). All of the Upper Paleolithic specimens except the Dolní Vstonice 35 femur are from intentional burials (graves). All the Neandertal specimens are isolated skeletal elements. The Upper Paleolithic Mal'ta 1 and Sunghir 2 and 3 fossils and the Neandertal Scladina 1 specimens are juveniles or young adolescents; the remainder were fully mature at the time of death.
Because stable isotope analyses are destructive and require good collagen preservation, suitable human remains are few in number. It is not unusual for bone samples from this time period to fail the requirements for analysis because of significant protein diagenesis. We assume that the available samples are sufficiently representative for our purposes, while recognizing that information (specifically on geographic and interpopulation diversity) is limited by the nature of these samples.
Mammal bone collagen 13C values measure the relative amounts of marine vs. terrestrial protein in the diet (15). In arid regions where there are significant numbers of C4 plants, the 13C value also can indicate the relative amounts of dietary protein from C3 and C4 plant sources (16); because C4 plants are unknown from prehistoric Europe (17), it is unlikely that the 13C values presented here reflect the differential plant consumption documented in arid equatorial environments. Consumer collagen 15N values are 2-4 higher than the average 15N value of the protein consumed. Therefore, in the Pleistocene human foraging context of concern here, 15N values indicate the trophic level of the organism of interest (18). Aquatic systems have longer food chains than terrestrial ones, and the 15N values of modern aquatic species such as fish (about 12 ) and carnivorous marine mammals (ca. 18 ) are much higher than those of terrestrial herbivores such as cattle and red deer (ca. 4-6 ; refs. 9, 19-25). The same would apply to waterfowl feeding on aquatic invertebrates and/or vertebrates (18). Thus, humans who consume significant amounts of aquatic foods will have much higher 15N values than humans who consume only terrestrial plants and herbivores (16, 25-28). For more extensive discussions of the assumptions and justifications behind these palaeodietary inferences from stable isotope analyses see refs. 29-31.
Additionally, marine organisms are more enriched in 13C than terrestrial organisms (15), such that, in addition to higher 15N values, marine organisms have more positive 13C values [e.g., 12 ± 1 for marine mammals (19)]. Organisms in freshwater ecosystems can have 13C values that are more negative than those in terrestrial and marine ecosystems, because carbon in freshwater systems can come from geological sources as well as from the atmosphere (32). Significant consumption of freshwater resources by humans therefore can be indicated by high 15N values and/or more negative 13C values [e.g., 23 ± 1 (33)]. For comparison, stable isotope values of Holocene late Mesolithic humans from Europe, whose diets (on the basis of zooarcheological evidence) included significant amounts of aquatic foods, are given in Table 1. There are, unfortunately, very few published 15N values for Eurasian freshwater fish and waterfowl; the available 13C and 15N values for a number of Eurasian freshwater and anadromous fish and waterfowl are given in Table 2.
Table1:
http://www.pnas.org/cgi/content/full/98/11/6528/T1
Table2:
http://www.pnas.org/cgi/content/full/98/11/6528/T2
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