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Dogs, a crane (not duck) and diet at Star Carr: a response to Schulting and Richards
Journal of
Archaeological SCIENCE Journal of Archaeological Science 30 (2003) 1353–1356 http://www.elsevier.com/locate/jas
Dogs, a crane (not duck) and diet at Star Carr: a response to Schulting and Richards Petra Dark a* Department of Archaeology, University of Reading, Whiteknights, PO Box 227, Reading RG6 6AB, UK Received 4 October 2002; received in revised form 3 February 2003; accepted 4 February 2003
Abstract In a recent article in this journal, Schulting and Richards (J Archaeol Sci 29 (2002) 327) present new carbon and nitrogen isotope analyses of bones from two dogs (Canis familiaris) and a common crane (Grus grus) from the early Mesolithic sites of Star Carr and Seamer Carr, in the Vale of Pickering, north-east England (Excavations at Star Carr (1954); The Mesolithic in Europe (1989) 218). These, they argue, undermine my previous suggestion (J Archaeol Sci 23 (1996) 783) that the 13C values for the Seamer dog obtained by Clutton-Brock and Noe-Nygaard (J Archaeol Sci 17 (1990) 643) could be explained by consumption not of marine foods, as originally interpreted, but from a diet that included foods from the freshwater carbonate-rich lake. Here I discuss Schulting and Richard’s new results and conclude that neither of the Vale of Pickering dogs need necessarily have consumed marine foods. Furthermore, the choice of a crane to test my suggestion that animals feeding on foods from the lake could have elevated 13C values is inappropriate because the diet of this bird is unlikely to have included a significant component of freshwater foods. Schulting and Richard’s new data do not, therefore, provide evidence for seasonal movement of early Mesolithic human groups between the coast and the inland lake. 2003 Elsevier Ltd. All rights reserved. Keywords: Star Carr; Seamer Carr; Mesolithic; Dog (Canis familiaris); Common crane (Grus grus); Stable carbon isotopes; Stable nitrogen isotopes
1. Introduction In a recent article in this journal, Schulting and Richards [17] present new carbon and nitrogen isotope analyses of bones from two dogs (Canis familiaris) and a common crane (Grus grus) (which they describe as the “duck” of their title!) from the early Mesolithic sites of Star Carr and Seamer Carr, in the Vale of Pickering, north-east England [1,14]. Their article follows my discussion [8] of previous carbon isotope analysis on dog bones from Seamer Carr by Clutton-Brock and Noe-Nygaard [2], which were originally interpreted as suggesting that the dog, and probably the human group with which it was associated, had consumed foods of marine origin. The purpose of my 1996 article was to point out that the carbonate-rich waters of the lake a Formerly Day. * Corresponding author. E-mail address: [email protected] (P. Dark).
0305-4403/03/$ - see front matter 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0305-4403(03)00026-8
produce 13C signatures in aquatic plants similar to those of marine foods, as demonstrated by analyses of remains of Potamogeton, a submerged aquatic, from the Mesolithic lake deposits. Food chains based on the lake resources could thus appear to show a marine effect. Schulting and Richards (S & R hereafter) remeasured the carbon isotope values of the Seamer Carr dog originally analysed by Clutton-Brock and Noe-Nygaard, and produced new analyses for a dog and a crane from Star Carr. These, along with their nitrogen isotope analyses, were argued to indicate that the Seamer Carr dog did consume marine protein, while the Star Carr dog did not. The crane did not have an enriched 13C value which, they argued, indicates that lake-based food chains in the Vale of Pickering do not show a “hard water” effect. These new analyses are, of course, a welcome addition to the debate on food resource use in the Vale of Pickering, especially as they are the first isotope analyses on bones from Star Carr itself (see Table 1 for selected
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P. Dark / Journal of Archaeological Science 30 (2003) 1353–1356
Table 1 Results of selected C and all N isotope analyses on plant and animal remains from Star Carr and Seamer Carr Site
Species
13C (‰)
15N (‰)
Source
Seamer Carr Seamer Carr Star Carr Star Carr Seamer Carr Star Carr (open-water marl) Star Carr (lake-edge muds)
Canis familiaris (dog) Canis familiaris (dog) Canis familiaris (dog) Grus grus (crane) Cervus elaphus (red deer) Potamogeton (pondweed) Misc. terrestrial plant remains
15.8 (average of 2)* 16.5 19.0 20.1 22.7 15.3 (average of 2) 27.7 (average of 12)
– 12.3 11.2 8.7 – – –
[2] [17] [17] [17] [2] [8] [8]
The two values obtained by Clutton-Brock and Noe-Nygaard were 14.67‰ and 16.97‰, hence rounded average of 15.8, not 15.3 as cited by Schulting and Richards. *
carbon and all nitrogen isotope results from the Vale of Pickering). I do not accept, however, that they undermine the arguments I presented in 1996, or that they provide any further support for S & R’s contention that “there could have been seasonal movements between the coast and inland” (p. 327) by peoples connected with the site at Seamer Carr. Here I begin by addressing the general points raised by S & R, which they suggest might mitigate against my arguments that the isotopic signature from the Seamer dog could have derived from the lake system. I then address the significance of their new results, particularly the extent to which the isotopic analysis of the crane has any bearing on the question of the effects of consumption of freshwater foods. 2. Differential preservation of faunal remains In relation to the potential use of resources from the lake, S & R point out that molluscs, fish and waterfowl are “very poorly represented at the sites, which are dominated by medium and large mammals” (p. 328). While they do raise the possibility that this could reflect differential preservation, their conclusions take the faunal assemblages at face value. As I pointed out in my original paper (p. 785), differential preservation is, in fact, highly likely to explain the lack of fish bones and molluscs and paucity of remains of birds and other small animals at Star Carr. This derives from the properties of the deposits containing the archaeological assemblage and is clearly demonstrated by comparing the plant and animal remains preserved in the reedswamp detritus muds in which the Star Carr “platform” was located with contemporary calcareous marl from the open water part of the lake. No molluscs were found either in Clark’s excavations or in subsequent detailed examination of the lake-edge reedswamp deposits [12], but molluscs were present in the contemporary open-water marl deposits [13]. Similarly, oospores of the aquatic alga, Chara (stonewort), were abundant in the marl and encrusted with calcium carbonate, whereas Chara
oospores in the lake-edge muds lacked a carbonate layer [5,6]. This is because the lake-edge muds associated with the occupation are mildly acidic in pH and therefore unsuitable for preservation of mollusc shells and small bones. This is further apparent from the decalcified state of even the large mammal bones [2], so it is hardly surprising that bones of fish and other small animals, such as amphibians, are not preserved. This is a clear case of “absence of evidence is not evidence of absence”—nothing can be inferred from the lack of bones of fish, other small animals, or mollusc shells, in the lake-edge deposits because these deposits are highly unlikely to preserve them. Thus the statement by S & R that “aquatic resources of the lake itself may have been limited or of little interest—as inferred from the lack of fish remains and the paucity of birds” (p. 331) is not valid. It cannot be argued that fish were not part of the diet because, even if the site has been littered with fish bones, they would no longer survive. 3. Use of aquatic plant resources S & R (p. 328) suggest that my “key proposition, that deep-water (sub-mergent) plants will be the basis of appropriate foodchains entered into at various levels by humans, is problematic”. I did not argue that the human or canine diet included a significant component of such plant foods (and in fact pointed out the limited evidence for this), but that it may have involved consumption of animals (such as fish) whose isotope values were influenced directly by consumption of such plants, or invertebrates which had fed on them. As there are no fish bones preserved at the site, it is not possible to test the hypothesis that consumption of freshwater fish could have produced marine-like isotope values in the Vale of Pickering region. Freshwater fish elsewhere have, however, sometimes been found to have elevated 13C values (e.g. [10,11,15]). Furthermore, consumption of such fish has been argued to account for enriched 13C values in Neolithic human bones from the Lake Baikal region of Siberia [11].
P. Dark / Journal of Archaeological Science 30 (2003) 1353–1356
4. Mollusca and the source of aquatic detritus S & R (p. 328) argue that terrestrial organic matter is abundant in lakes and that such material would influence the diet of detritus-feeding molluscs, so their meat would probably have terrestrial 13C values. In fact, detailed analysis of plant remains from the former lake at Star Carr [6] indicated that detritus accumulating in open water—likely to have been inhabited by molluscs such as freshwater mussels (Anodonta and Unio)— derived almost entirely from aquatic plants, especially Potamogeton (pondweed) leaves and stems. It is therefore entirely reasonable to assume that molluscs were feeding on submerged aquatic plant material. 5. Introduction of marine isotope signatures by fish and birds R & S (p. 329) discuss the fact that most of the bird species found at the site are migratory and may have inhabited coastal areas outside the breeding season, so are not representative of lake-based foodchains. Anadromous fish would also introduce a marine isotope signature. These are points that I made in my original paper to indicate that they provided another way in which a “marine” signature could be introduced without human groups moving to the coast (p. 785). Such birds, while in the Vale of Pickering, can fairly be described as part of the lake’s food web. 6. The crane and hypothesis testing S & R apparently chose the bone of a crane for analysis on the grounds that this species “must have fed from the lake and streams of the area” (p. 330), and was unlikely to have moved between the coast and inland waters (so avoiding confusion with a truly marine isotope signature). The carbon isotope result of 20.1‰ is, as they state, “entirely terrestrial”, as is the nitrogen result. S & R argue that this 13C value undermines my proposition that lake-based food chains could have been affected by carbonate enrichment of the lake waters. Unfortunately, S & R appear to be confused about the ecology of the common crane. Not only do they refer to it as a “duck” in their title, but having described it (three times) in their abstract as an “aquatic bird”, they then go on to state that it is “one of the species most likely to be solely terrestrial” (p. 329). To clarify, while the common crane is sometimes loosely described as a “waterbird”, this refers to its preferred habitat of wetlands such as reedswamps and does not mean that it fed on submerged aquatic foods. In fact, the common crane feeds predominantly on terrestrial plants (roots, stems, leaves, fruits and seeds) and animals (especially invertebrates such as insects, molluscs and earthworms) [3].
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Taking the average value for terrestrial plant remains (using atmospheric carbon) from Star Carr (Table 1) of 27.7‰ (range 29.2 to 25.7), herbivores consuming such plants would be expected to have bone collagen values c. 5‰ higher [18], i.e. c. 22.7‰ (exactly the result obtained by Clutton-Brock & Noe-Nygaard for the red deer bone from Seamer Carr), while carnivores feeding on them would have bone collagen values enriched by a further c. 2‰, resulting in values of c. 20.7‰. The carbon isotope value for the crane bone is close to the latter figure and, given the actual range in 13C demonstrated in the plant materials, entirely consistent with a diet based on a mixture of plants and animals of terrestrial origin. To test the hypothesis that the meat of waterfowl was affected by consumption of aquatic plants or animals it is obviously necessary to choose birds whose diet would have been largely based on such material. S & R’s results are thus not “contrary to expectations” deriving from my position because the diet of the crane is unlikely to have contained a significant element of foods from the lake. 7. The dogs S & R’s carbon isotope results from the Star Carr dog are described by them as indicating “at most only a slight contribution of marine foods”, while the nitrogen value “could reflect some contribution of freshwater fish” (p. 330). The slight “marine” signature from the carbon isotope could also, of course, result from consumption of freshwater fish with carbon isotopes affected by the “hard-water” lake. The measured value of 19.0‰ is only slightly higher than that calculated above (c. 20.7‰) as likely to occur in entirely terrestrial food chains, so any contribution of fish or other freshwater food to the diet of this animal is indeed likely to have been small. Nitrogen isotopes provide an indication of the trophic level of an organism, increasing by c. 3‰ at each step in a food chain [15]. Values tend to be higher in marine and freshwater ecosystems because food chains are often longer than in terrestrial environments. Although S & R suggest that the nitrogen isotope value for the Star Carr dog could be slightly elevated due to consumption of food from the lake, the result from the crane suggests that a dog consuming birds or other terrestrial animals with a similar 15N would have bone collagen values of c. 11.7‰. This is close to the actual value for the Star Carr dog, so both the carbon and nitrogen analyses for this animal point to a largely terrestrial diet. For the Seamer Carr dog S & R argue that “the elevated 13C and 15N values . suggest that marine foods did indeed comprise about 50% of the animal’s dietary protein” (p. 330). Their carbon isotope value is
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P. Dark / Journal of Archaeological Science 30 (2003) 1353–1356
similar to that obtained by Clutton-Brock and NoeNygaard [2]—indeed more so than S & R’s paper suggests, as they miscalculate the average of Clutton-Brock and Noe-Nygaard’s results as 15.3‰, rather than the correct figure of 15.8‰. In the light of the discussion in the first half of this paper, I would argue that the points I made in 1996 still apply. As mentioned above, elevated 15N values can occur in both marine and freshwater food chains, so the nitrogen result could similarly be explained by access to lake-based food chains. 8. Chronology A final point concerns the chronologies of human activity at Star Carr and Seamer Carr. S & R quote the date of Seamer Carr and Star Carr as c. 9900 BP. Although a radiocarbon date on the Seamer Carr dog gave a result of 9940100 BP (OxA-1030) [2], other dates from the Seamer excavations suggest that activity focused around 9300 BP [14]. For Star Carr the recent detailed programme of radiocarbon accelerator dating indicates a date of c. 9600 BP [4,7,9]. This coincides with a plateau in the radiocarbon calibration curve, but wiggle-matching has produced a date of 10,920 cal BP (8970 cal BC) for the start of the first of two phases of activity at the site [7]. 9. Conclusion The results of S & R are a useful addition to the small number of isotope analyses from animal remains associated with early Mesolithic sites in Britain (see also [16]). They do not, however, necessarily provide evidence for consumption of marine foods by early Mesolithic dogs in the Vale of Pickering. The Star Carr dog could have subsisted entirely on terrestrial foods, while both the carbon and nitrogen isotope results for the Seamer dog are explicable in terms of a diet that included consumption of foods from the lake, such as fish or shellfish. Furthermore, their results do not undermine my suggestion that food chains based in the hard-water lake could produce isotope values that mimic those based on marine foods because the diet of the bird they analysed to test this hypothesis is unlikely to have included a significant component of submerged plants or animals from the lake. The results thus provide no support for the suggestion of seasonal movements by human groups in the Vale of Pickering to the coast. Acknowledgements I thank Professor K. D. Bennett and an anonymous referee for helpful comments on an earlier version of this paper.
References [1] J.G.D. Clark, Excavations at Star Carr, Cambridge University Press, Cambridge, 1954. [2] J. Clutton-Brock, N. Noe-Nygaard, New osteological and C-isotope evidence on Mesolithic dogs: companions to hunters and fishers at Star Carr, Seamer Carr and Kongemose, Journal of Archaeological Science 17 (1990) 643–653. [3] S. Cramp (Ed.), Handbook of the Birds of Europe, the Middle East and North Africa. The Birds of the Western Palearctic. Volume II Hawks to Bustards, Oxford University Press, Oxford, 1980. [4] P. Dark, Radiocarbon dating of the lake-edge deposits, in: P. Mellars, P. Dark, Star Carr in Context, McDonald Institute, Cambridge, 1998, pp. 119–124. [5] P. Dark, Lake-edge sequence: results, in: P. Mellars, P. Dark, Star Carr in Context, McDonald Institute, Cambridge, 1998, pp. 125–146. [6] P. Dark, The lake-centre sequence: results, in: P. Mellars, P. Dark, Star Carr in Context, McDonald Institute, Cambridge, 1998, pp. 163–178. [7] P. Dark, Revised ‘absolute’ dating of the early Mesolithic site of Star Carr, North Yorkshire, in the light of changes in the early Holocene tree-ring chronology, Antiquity 74 (2000) 304–307. [8] S.P. Day, Dogs, deer and diet at Star Carr: a reconsideration of C-isotope evidence from early Mesolithic dog remains from the Vale of Pickering, Yorkshire, England, Journal of Archaeological Science 23 (1996) 783–787. [9] S.P. Day, P.A. Mellars, ‘Absolute’ dating of Mesolithic human activity at Star Carr, Yorkshire: new palaeoecological studies and identification of the 9600 BP radiocarbon ‘plateau’, Proceedings of the Prehistoric Society 60 (1994) 417–422. [10] M.A. Katzenberg, Stable isotope analysis of archaeological faunal remains from Southern Ontario, Journal of Archaeological Science 16 (1989) 319–329. [11] M.A. Katzenberg, Stable isotope ecology and palaeodiet in the Lake Baikal region of Siberia, Journal of Archaeological Science 26 (1999) 651–659. [12] P. Mellars, P. Dark, Star Carr in Context, McDonald Institute, Cambridge, 1998. [13] R.C. Preece, The molluscan succession from Holocene lake marls at Star Carr, in: P. Mellars, P. Dark (Eds.), Star Carr in Context, McDonald Institute, Cambridge, 1998, pp. 172–175. [14] R.T. Schadla-Hall, The Vale of Pickering in the early Mesolithic in context, in: C. Bonsall (Ed.), The Mesolithic in Europe, John Donald, Edinburgh, 1989, pp. 218–224. [15] M.J. Schoeninger, M.J. DeNiro, Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals, Geochimica et Cosmochimica Acta 48 (1984) 625–639. [16] R.J. Schulting, M.P. Richards, The use of stable isotopes in studies of subsistence and seasonality in the British Mesolithic, in: R. Young (Ed.), Mesolithic Lifeways: Current Research from Britain and Ireland, University of Leicester, Leicester, 2000, pp. 55–65. [17] R.J. Schulting, M.P. Richards, Dogs, ducks, deer and diet: new stable isotope evidence on early Mesolithic dogs from the Vale of Pickering, north-east England, Journal of Archaeological Science 29 (2002) 327–333. [18] N.J. Van der Merwe, Light stable isotopes and the reconstruction of prehistoric diets, Proceedings of the British Academy 77 (1992) 247–264.
Archaeological SCIENCE Journal of Archaeological Science 30 (2003) 1353–1356 http://www.elsevier.com/locate/jas
Dogs, a crane (not duck) and diet at Star Carr: a response to Schulting and Richards Petra Dark a* Department of Archaeology, University of Reading, Whiteknights, PO Box 227, Reading RG6 6AB, UK Received 4 October 2002; received in revised form 3 February 2003; accepted 4 February 2003
Abstract In a recent article in this journal, Schulting and Richards (J Archaeol Sci 29 (2002) 327) present new carbon and nitrogen isotope analyses of bones from two dogs (Canis familiaris) and a common crane (Grus grus) from the early Mesolithic sites of Star Carr and Seamer Carr, in the Vale of Pickering, north-east England (Excavations at Star Carr (1954); The Mesolithic in Europe (1989) 218). These, they argue, undermine my previous suggestion (J Archaeol Sci 23 (1996) 783) that the 13C values for the Seamer dog obtained by Clutton-Brock and Noe-Nygaard (J Archaeol Sci 17 (1990) 643) could be explained by consumption not of marine foods, as originally interpreted, but from a diet that included foods from the freshwater carbonate-rich lake. Here I discuss Schulting and Richard’s new results and conclude that neither of the Vale of Pickering dogs need necessarily have consumed marine foods. Furthermore, the choice of a crane to test my suggestion that animals feeding on foods from the lake could have elevated 13C values is inappropriate because the diet of this bird is unlikely to have included a significant component of freshwater foods. Schulting and Richard’s new data do not, therefore, provide evidence for seasonal movement of early Mesolithic human groups between the coast and the inland lake. 2003 Elsevier Ltd. All rights reserved. Keywords: Star Carr; Seamer Carr; Mesolithic; Dog (Canis familiaris); Common crane (Grus grus); Stable carbon isotopes; Stable nitrogen isotopes
1. Introduction In a recent article in this journal, Schulting and Richards [17] present new carbon and nitrogen isotope analyses of bones from two dogs (Canis familiaris) and a common crane (Grus grus) (which they describe as the “duck” of their title!) from the early Mesolithic sites of Star Carr and Seamer Carr, in the Vale of Pickering, north-east England [1,14]. Their article follows my discussion [8] of previous carbon isotope analysis on dog bones from Seamer Carr by Clutton-Brock and Noe-Nygaard [2], which were originally interpreted as suggesting that the dog, and probably the human group with which it was associated, had consumed foods of marine origin. The purpose of my 1996 article was to point out that the carbonate-rich waters of the lake a Formerly Day. * Corresponding author. E-mail address: [email protected] (P. Dark).
0305-4403/03/$ - see front matter 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0305-4403(03)00026-8
produce 13C signatures in aquatic plants similar to those of marine foods, as demonstrated by analyses of remains of Potamogeton, a submerged aquatic, from the Mesolithic lake deposits. Food chains based on the lake resources could thus appear to show a marine effect. Schulting and Richards (S & R hereafter) remeasured the carbon isotope values of the Seamer Carr dog originally analysed by Clutton-Brock and Noe-Nygaard, and produced new analyses for a dog and a crane from Star Carr. These, along with their nitrogen isotope analyses, were argued to indicate that the Seamer Carr dog did consume marine protein, while the Star Carr dog did not. The crane did not have an enriched 13C value which, they argued, indicates that lake-based food chains in the Vale of Pickering do not show a “hard water” effect. These new analyses are, of course, a welcome addition to the debate on food resource use in the Vale of Pickering, especially as they are the first isotope analyses on bones from Star Carr itself (see Table 1 for selected
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P. Dark / Journal of Archaeological Science 30 (2003) 1353–1356
Table 1 Results of selected C and all N isotope analyses on plant and animal remains from Star Carr and Seamer Carr Site
Species
13C (‰)
15N (‰)
Source
Seamer Carr Seamer Carr Star Carr Star Carr Seamer Carr Star Carr (open-water marl) Star Carr (lake-edge muds)
Canis familiaris (dog) Canis familiaris (dog) Canis familiaris (dog) Grus grus (crane) Cervus elaphus (red deer) Potamogeton (pondweed) Misc. terrestrial plant remains
15.8 (average of 2)* 16.5 19.0 20.1 22.7 15.3 (average of 2) 27.7 (average of 12)
– 12.3 11.2 8.7 – – –
[2] [17] [17] [17] [2] [8] [8]
The two values obtained by Clutton-Brock and Noe-Nygaard were 14.67‰ and 16.97‰, hence rounded average of 15.8, not 15.3 as cited by Schulting and Richards. *
carbon and all nitrogen isotope results from the Vale of Pickering). I do not accept, however, that they undermine the arguments I presented in 1996, or that they provide any further support for S & R’s contention that “there could have been seasonal movements between the coast and inland” (p. 327) by peoples connected with the site at Seamer Carr. Here I begin by addressing the general points raised by S & R, which they suggest might mitigate against my arguments that the isotopic signature from the Seamer dog could have derived from the lake system. I then address the significance of their new results, particularly the extent to which the isotopic analysis of the crane has any bearing on the question of the effects of consumption of freshwater foods. 2. Differential preservation of faunal remains In relation to the potential use of resources from the lake, S & R point out that molluscs, fish and waterfowl are “very poorly represented at the sites, which are dominated by medium and large mammals” (p. 328). While they do raise the possibility that this could reflect differential preservation, their conclusions take the faunal assemblages at face value. As I pointed out in my original paper (p. 785), differential preservation is, in fact, highly likely to explain the lack of fish bones and molluscs and paucity of remains of birds and other small animals at Star Carr. This derives from the properties of the deposits containing the archaeological assemblage and is clearly demonstrated by comparing the plant and animal remains preserved in the reedswamp detritus muds in which the Star Carr “platform” was located with contemporary calcareous marl from the open water part of the lake. No molluscs were found either in Clark’s excavations or in subsequent detailed examination of the lake-edge reedswamp deposits [12], but molluscs were present in the contemporary open-water marl deposits [13]. Similarly, oospores of the aquatic alga, Chara (stonewort), were abundant in the marl and encrusted with calcium carbonate, whereas Chara
oospores in the lake-edge muds lacked a carbonate layer [5,6]. This is because the lake-edge muds associated with the occupation are mildly acidic in pH and therefore unsuitable for preservation of mollusc shells and small bones. This is further apparent from the decalcified state of even the large mammal bones [2], so it is hardly surprising that bones of fish and other small animals, such as amphibians, are not preserved. This is a clear case of “absence of evidence is not evidence of absence”—nothing can be inferred from the lack of bones of fish, other small animals, or mollusc shells, in the lake-edge deposits because these deposits are highly unlikely to preserve them. Thus the statement by S & R that “aquatic resources of the lake itself may have been limited or of little interest—as inferred from the lack of fish remains and the paucity of birds” (p. 331) is not valid. It cannot be argued that fish were not part of the diet because, even if the site has been littered with fish bones, they would no longer survive. 3. Use of aquatic plant resources S & R (p. 328) suggest that my “key proposition, that deep-water (sub-mergent) plants will be the basis of appropriate foodchains entered into at various levels by humans, is problematic”. I did not argue that the human or canine diet included a significant component of such plant foods (and in fact pointed out the limited evidence for this), but that it may have involved consumption of animals (such as fish) whose isotope values were influenced directly by consumption of such plants, or invertebrates which had fed on them. As there are no fish bones preserved at the site, it is not possible to test the hypothesis that consumption of freshwater fish could have produced marine-like isotope values in the Vale of Pickering region. Freshwater fish elsewhere have, however, sometimes been found to have elevated 13C values (e.g. [10,11,15]). Furthermore, consumption of such fish has been argued to account for enriched 13C values in Neolithic human bones from the Lake Baikal region of Siberia [11].
P. Dark / Journal of Archaeological Science 30 (2003) 1353–1356
4. Mollusca and the source of aquatic detritus S & R (p. 328) argue that terrestrial organic matter is abundant in lakes and that such material would influence the diet of detritus-feeding molluscs, so their meat would probably have terrestrial 13C values. In fact, detailed analysis of plant remains from the former lake at Star Carr [6] indicated that detritus accumulating in open water—likely to have been inhabited by molluscs such as freshwater mussels (Anodonta and Unio)— derived almost entirely from aquatic plants, especially Potamogeton (pondweed) leaves and stems. It is therefore entirely reasonable to assume that molluscs were feeding on submerged aquatic plant material. 5. Introduction of marine isotope signatures by fish and birds R & S (p. 329) discuss the fact that most of the bird species found at the site are migratory and may have inhabited coastal areas outside the breeding season, so are not representative of lake-based foodchains. Anadromous fish would also introduce a marine isotope signature. These are points that I made in my original paper to indicate that they provided another way in which a “marine” signature could be introduced without human groups moving to the coast (p. 785). Such birds, while in the Vale of Pickering, can fairly be described as part of the lake’s food web. 6. The crane and hypothesis testing S & R apparently chose the bone of a crane for analysis on the grounds that this species “must have fed from the lake and streams of the area” (p. 330), and was unlikely to have moved between the coast and inland waters (so avoiding confusion with a truly marine isotope signature). The carbon isotope result of 20.1‰ is, as they state, “entirely terrestrial”, as is the nitrogen result. S & R argue that this 13C value undermines my proposition that lake-based food chains could have been affected by carbonate enrichment of the lake waters. Unfortunately, S & R appear to be confused about the ecology of the common crane. Not only do they refer to it as a “duck” in their title, but having described it (three times) in their abstract as an “aquatic bird”, they then go on to state that it is “one of the species most likely to be solely terrestrial” (p. 329). To clarify, while the common crane is sometimes loosely described as a “waterbird”, this refers to its preferred habitat of wetlands such as reedswamps and does not mean that it fed on submerged aquatic foods. In fact, the common crane feeds predominantly on terrestrial plants (roots, stems, leaves, fruits and seeds) and animals (especially invertebrates such as insects, molluscs and earthworms) [3].
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Taking the average value for terrestrial plant remains (using atmospheric carbon) from Star Carr (Table 1) of 27.7‰ (range 29.2 to 25.7), herbivores consuming such plants would be expected to have bone collagen values c. 5‰ higher [18], i.e. c. 22.7‰ (exactly the result obtained by Clutton-Brock & Noe-Nygaard for the red deer bone from Seamer Carr), while carnivores feeding on them would have bone collagen values enriched by a further c. 2‰, resulting in values of c. 20.7‰. The carbon isotope value for the crane bone is close to the latter figure and, given the actual range in 13C demonstrated in the plant materials, entirely consistent with a diet based on a mixture of plants and animals of terrestrial origin. To test the hypothesis that the meat of waterfowl was affected by consumption of aquatic plants or animals it is obviously necessary to choose birds whose diet would have been largely based on such material. S & R’s results are thus not “contrary to expectations” deriving from my position because the diet of the crane is unlikely to have contained a significant element of foods from the lake. 7. The dogs S & R’s carbon isotope results from the Star Carr dog are described by them as indicating “at most only a slight contribution of marine foods”, while the nitrogen value “could reflect some contribution of freshwater fish” (p. 330). The slight “marine” signature from the carbon isotope could also, of course, result from consumption of freshwater fish with carbon isotopes affected by the “hard-water” lake. The measured value of 19.0‰ is only slightly higher than that calculated above (c. 20.7‰) as likely to occur in entirely terrestrial food chains, so any contribution of fish or other freshwater food to the diet of this animal is indeed likely to have been small. Nitrogen isotopes provide an indication of the trophic level of an organism, increasing by c. 3‰ at each step in a food chain [15]. Values tend to be higher in marine and freshwater ecosystems because food chains are often longer than in terrestrial environments. Although S & R suggest that the nitrogen isotope value for the Star Carr dog could be slightly elevated due to consumption of food from the lake, the result from the crane suggests that a dog consuming birds or other terrestrial animals with a similar 15N would have bone collagen values of c. 11.7‰. This is close to the actual value for the Star Carr dog, so both the carbon and nitrogen analyses for this animal point to a largely terrestrial diet. For the Seamer Carr dog S & R argue that “the elevated 13C and 15N values . suggest that marine foods did indeed comprise about 50% of the animal’s dietary protein” (p. 330). Their carbon isotope value is
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P. Dark / Journal of Archaeological Science 30 (2003) 1353–1356
similar to that obtained by Clutton-Brock and NoeNygaard [2]—indeed more so than S & R’s paper suggests, as they miscalculate the average of Clutton-Brock and Noe-Nygaard’s results as 15.3‰, rather than the correct figure of 15.8‰. In the light of the discussion in the first half of this paper, I would argue that the points I made in 1996 still apply. As mentioned above, elevated 15N values can occur in both marine and freshwater food chains, so the nitrogen result could similarly be explained by access to lake-based food chains. 8. Chronology A final point concerns the chronologies of human activity at Star Carr and Seamer Carr. S & R quote the date of Seamer Carr and Star Carr as c. 9900 BP. Although a radiocarbon date on the Seamer Carr dog gave a result of 9940100 BP (OxA-1030) [2], other dates from the Seamer excavations suggest that activity focused around 9300 BP [14]. For Star Carr the recent detailed programme of radiocarbon accelerator dating indicates a date of c. 9600 BP [4,7,9]. This coincides with a plateau in the radiocarbon calibration curve, but wiggle-matching has produced a date of 10,920 cal BP (8970 cal BC) for the start of the first of two phases of activity at the site [7]. 9. Conclusion The results of S & R are a useful addition to the small number of isotope analyses from animal remains associated with early Mesolithic sites in Britain (see also [16]). They do not, however, necessarily provide evidence for consumption of marine foods by early Mesolithic dogs in the Vale of Pickering. The Star Carr dog could have subsisted entirely on terrestrial foods, while both the carbon and nitrogen isotope results for the Seamer dog are explicable in terms of a diet that included consumption of foods from the lake, such as fish or shellfish. Furthermore, their results do not undermine my suggestion that food chains based in the hard-water lake could produce isotope values that mimic those based on marine foods because the diet of the bird they analysed to test this hypothesis is unlikely to have included a significant component of submerged plants or animals from the lake. The results thus provide no support for the suggestion of seasonal movements by human groups in the Vale of Pickering to the coast. Acknowledgements I thank Professor K. D. Bennett and an anonymous referee for helpful comments on an earlier version of this paper.
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