Results and discussion

Bulk carbon and nitrogen isotope analysis was conducted on 68 carbonised surface deposits (65 interior and 3 exterior deposits) that were adhering to 44 individual pots, in order to provide some crude indication of their use. Despite some variability, potsherds from coastal sites (n = 19) are significantly enriched in ¹³C and ¹⁵N compared with those from inland sites (n = 25; Figure 3A; Mann–Whitney U test;¹³C value: U = 1020, P = < 0.001; ¹⁵N value: U = 967, P = < 0.001), a distinction attributable to a greater incorporation of isotopically heavier marine foods (Craig et al. Reference Craig, Steeleb, Fischer, Hartz, Andersen, Donohoe, Glykou, Saul, Jones, Koch and Heron2011). The source contributions to the carbonised deposits from pots from inland sites is more difficult to determine based on bulk isotope characteristics alone, as freshwater fish and terrestrial foods are both depleted in ¹³C. The carbon isotope value is also almost certainly affected by differential preservation of different classes of biomolecules (Craig et al. Reference Craig, Forster, Andersen, Koch, Crombé, Milner, Stern, Bailey and Heron2007). Charred deposits from inland sites have δ¹⁵N values that fall within the range of experimentally charred foods from both terrestrial and aquatic animals (Figure 3A), possibly indicating a more complex mixture of sources. Notably, all Vinette 1 vessels have δ¹⁵N values well above the median for terrestrial animals and none are consistent with plant foods.

Figure 3.

Bulk and single compound stable isotope data from Vinette 1 pottery from coastal (open circles) and inland/riverine sites (filled circles). A) Bulk stable carbon and nitrogen isotope of interior surface deposits. Exterior deposits (star symbols) and the median and ranges (2σ) of experimentally charred aquatic and terrestrial animals (Craig et al. Reference Craig, Saul, Lucquin, Nishida, Taché, Clarkes, Thompson, Altoft, Uchiyama, Ajimoto, Gibbs, Isaksson, Heron and Jordan2013) are also shown. B) Plot of the δ¹³C values of C _{16: 0} and C _{18: 0} fatty acids extracted from Vinette 1 potsherds. Samples that have aquatic biomarkers are shown in blue. Extracts from surface deposits from inland/riverine sites are represented by filled squares. These are compared with reference fats from wild ruminant (n = 19), freshwater (n = 24) and marine (n = 22) organisms (see online supplementary Table S2) plotted as confidence ellipses (1σ; Stastica v.7). Additional North American authentic fat samples from wild herbivorous, omnivorous and piscivorous animals (n = 8) are indicated separately (open diamonds).

To provide more specific information on pottery use, lipids were successfully extracted from 143 ceramic samples (130 interior and 13 exterior samples) and 10 carbonised surface deposits (8 interior and 2 exterior deposits) from 112 vessels (Table 1). Analysis by gas chromatography mass spectrometry (GC-MS) revealed the presence of lipid biomarkers derived from aquatic organisms in a large number of pots from both coastal and inland sites. Of the inland vessels, 40 per cent (n = 29; Table 1) are characterised by the presence of at least one of three isoprenoid alkanoic acids (phytanic, pristanic or 4,8,12-TMTD), which are at high concentration in freshwater and marine organisms, and by a range of positional isomers of ω-(o-alkylphenyl)alkanoic acids containing a minimum of 20 carbon atoms, with trace amount of the C₂₂ homologue also detected in the majority of cases (Figure 4A). These suites of compounds can only be produced by the protracted heating of polyunsaturated fatty acids present in aquatic organisms (Hansel et al. Reference Hansel, Copley, Madurai and Evershed2004; Craig et al. Reference Craig, Forster, Andersen, Koch, Crombé, Milner, Stern, Bailey and Heron2007; Evershed et al. Reference Evershed, Copley, Dickson and Hansel2008).

Figure 4.

Examples of partial gas chromatograms of lipid extracts from different Vinette 1 potsherds. Also shown is the number of potsherds exhibiting similar chromatograms. A) Degraded aquatic oil from a potsherd excavated at the Eddy site, New Hampshire (NH38.6-5). The partial m/z 105 ion chromatogram (inset) shows ω-(o-alkylphenyl)alkanoic acids with 16 (+), 18 (*), 20 (#) and 22 (o) carbon atoms; B) degraded terrestrial animal fat from a potsherd (PB03) excavated at the Peace Bridge site; C) degraded possible plant oil from a potsherd (BB09) excavated at the Bruce Boyd site. Cn:x are fatty acids with carbon length n and number of unsaturations x; DCx are α,ω-dicarboxylic acids with carbon length x; ALx are alkanes with carbon length x; br are branched-chain acids; Kn are long chain ketones with carbon length n; p are plasticiser contaminants; IS is internal standard (n-hexatriacontane).

Table 1.

Summary of organic residue analysis results obtained from Vinette 1 pottery. Further details are available in online supplementary Table S1.

* > 5μg/g for ceramic samples, > 0.5μg/mg for carbonised deposits.

†Complete set of aquatic biomarkers defined by the presence of at least one of the three isoprenoid alkanoic acids (phytanic, pristanic or 4,8,12-TMTD) and ω-(o-alkylphenyl)alkanoic acids containing a minimum of 20 carbon atoms. Partial set of aquatic biomarkers defined by the presence of either one of the three isoprenoid alkanoic acids (phytanic, pristanic or 4,8,12-TMTD) or ω-(o-alkylphenyl)alkanoic acids containing a minimum of 20 carbon atoms.

A significant proportion of pots from coastal sites (53 per cent, n = 21) also contained similar arrays of biomarkers for aquatic foods (Table 1). These proportions represent only the minimum values as an absence of aquatic biomarkers does not mean that aquatic resources were not processed in pots. Firstly, the highly diagnostic ω-(o-alkylphenyl)alkanoic acids are only formed from parent polyunsaturated fatty acids under specific conditions, i.e. high temperature ( > 270 °C; Hansel et al. Reference Hansel, Copley, Madurai and Evershed2004), which are often difficult to replicate experimentally. Second, both these compounds and other diagnostic lipid components may have been lost through exposure to the burial environment. When considering Vinette 1 samples that yielded either isoprenoid or ω-(o-alkylphenyl)alkanoic acids containing a minimum of 20 carbon atoms, in addition to medium to long-chain saturated (C₁₄–C₂₄) and mono-unsaturated (C_{16: 1}–C_{22: 1}) fatty acids, which are also common to many aquatic oils, the proportion of vessels implicated in the processing of aquatic resources rises to 63 per cent (n = 45) from inland sites and 75 per cent (n = 30) from coastal sites. This is still a minimum estimate as a large number of samples are characterised by lipid profiles that could not be assigned to any food class due to extensive degradation. Overall, these data provide compelling evidence that Vinette 1 pottery vessels were principally used to process marine and freshwater faunal resources, such as fish, invertebrates or mammals.

Finally, GC-combustion-isotope ratio MS (GC-C-IRMS) analysis was carried out on 60 samples representing 52 individual vessels to investigate further the source of lipids recovered from the assemblage (Figure 2 B). By comparing the δ¹³C values of the most abundant n-alkanoic acids preserved in potsherds, i.e. octadecanoic (C_{18: 0}) and hexadecanoic (C_{16: 0}) acid, with corresponding values from authentic reference fats and oils, more specific identifications can be achieved (Dudd et al. Reference Dudd, Evershed and Gibson1999; Craig et al. Reference Craig, Allen, Thompson, Stevens, Steele and Heron2012, Reference Craig, Saul, Lucquin, Nishida, Taché, Clarkes, Thompson, Altoft, Uchiyama, Ajimoto, Gibbs, Isaksson, Heron and Jordan2013). Notably, reference fats from marine fish and marine mammals are consistently enriched in ¹³C compared with those from freshwater and terrestrial organisms (Figure 3B; see also online supplementary Table S2). Additionally, C_{18: 0} acids in ruminant animals are generally depleted in ¹³C by c. 1–6‰ compared with C_{16: 0} and, with the exception of Rangifer tarandus (caribou), which feeds partially on ¹³C-enriched lichens, the values are tightly constrained (Figure 3B). The carbon isotopic composition of fats from non-ruminant animals and freshwater fish are harder to discriminate. This is mainly because freshwater fish, which include diadromous and estuarine species, and animals that feed on freshwater organisms exhibit a broad range of values (Figure 3B), reflecting environmental variation in primary sources of carbon.

The δ¹³C values of individual fatty acids from Vinette 1 vessels from coastal sites (n = 15) are significantly enriched in ¹³C compared with those from inland sites (n = 45; e.g. for C_{16: 0,} Mann-Whitney U test; U = 98; P = < 0.001). This result is consistent with the preferential cooking of marine foods in pottery from coastal settings. Interestingly, three samples from inland riverine locations, all with aquatic biomarkers, have isotope values within the range (1σ) for marine fish. A likely explanation is that diadromous fish, such as shad, alewives, salmonids or eels, were processed in these vessels. A further three samples from coastal sites without any aquatic biomarker could be assigned to a marine origin based on their isotope characteristics. Overall, the fatty acid isotope data confirms that the vast majority of samples submitted for analysis are consistent with a marine or freshwater origin. In contrast, the evidence for ruminant lipids in Vinette 1 pottery is surprisingly limited considering the high abundance of deer and elk in temperate woodland environments. Two vessels, one each from Peace Bridge and Pointe-du-Buisson, have fatty acid δ¹³C values comparable with wild ruminant fats, although the identification of aquatic biomarkers in both of them suggests that fish and terrestrial meat were mixed or processed sequentially in these vessels. Of the entire sample of Vinette 1 pottery analysed, only seven vessels have lipid profiles characterised by an absence of aquatic biomarkers, low C_{16: 0}/C_{18: 0} ratios ( < 1), short-chain fatty acids, and odd or branched-chain fatty acids, which are typical of animal fats (Figure 4B). Similarly, lipid profiles typical of plant oils characterised by high C_{16: 0}/C_{18: 0} ratios (i.e. > 2), abundance of C_{12: 0} and C_{14: 0} fatty acids, and n-alkanes in the carbon-chain range C_{20: 0} to C_{35: 0} (Figure 4C), were only observed in a small number (n = 16) of the vessels analysed. Interestingly, a significant proportion of these come from just two sites, Dawson Creek and Scaccia. Other than these observations, there were no apparent regional differences in the use of pots. By comparing the residue analysis data with a recently compiled inventory of AMS dates (Taché & Hart Reference Taché and Hart2013), there was also no evidence of any chronological patterning in the use of Vinette 1 pottery. Vessels from across the study area were mainly associated with freshwater or marine resources.

The preference for the processing of aquatic resources in the earliest pottery from north-eastern North America is not a simple reflection of the wider subsistence strategy at the time. From the analysis of macroscopic food remains from these sites, it is clear that subsistence practices varied widely, both seasonally and geographically. Where comparable faunal data exists, marine fish appear to have been heavily exploited at coastal sites, particularly during the spring and summer (Belcher Reference Belcher1989). However, significant proportions of large and small terrestrial mammals are also present and these coastal groups are most accurately described as broad-spectrum opportunistic hunter-gatherers (Bunker 2006–Reference Craig, Forster, Andersen, Koch, Crombé, Milner, Stern, Bailey and Heron2007). At inland and riverine sites, terrestrial mammals, notably the whitetail deer (Odocoileus virginianus), consistently dominate faunal assemblages. For example, at the Riverhaven 2 site in the Niagara Peninsula, terrestrial mammals make up 82 per cent of the faunal assemblage, 38 per cent of the number of individuals identified, and 96 per cent of usable meat by weight (Granger Reference Granger1978). Of this, over half the meat was derived from whitetail deer despite the proximity of the site to productive fishing grounds and the good potential for the preservation of faunal remains. The fact that pottery was mainly used to process aquatic resources, most likely freshwater fish, is therefore perplexing given that deer fat must have been very abundant and is easily distinguishable through lipid residue analysis (Craig et al. Reference Craig, Allen, Thompson, Stevens, Steele and Heron2012).

Similarly, it is very unlikely that the fruits of forest trees, such as acorns or nuts, were significantly processed in early pottery from this region, despite the fact that such commodities were readily available and have been closely linked with the appearance of pottery in the Great Lakes region (Ozker Reference Ozker1982). The analysis of modern oil from several species of authentic wild mast (Juglans cinerea, Juglans nigra, Quercus alba, Quercus macrocarpa, Fagus grandifolia, Carya ovate, Corylus cornuta; n = 8) by GC-MS produced very low relative abundances of C_{18: 0} fatty acid (C_{16: 0}/C_{18: 0} = 4.5, ± 3.9 (s.d.); C_{18: 0}/total fatty acid = 0.03, ± 0.01 (s.d.)), whereas this compound was relatively abundant in a majority of archaeological pottery extracts (Figure 4A & 4B; online supplementary Table S1). The long-term exposure of nut oils to the burial environment would be expected to reduce the abundance of C_{16: 0} relative to C_{18: 0} through preferential dissolution, but this would also result in the almost complete loss of the even shorter chain acids that are observed in many of the samples (supplementary Table S1). The relatively high δ¹⁵N values observed from bulk isotope analysis of Vinette 1 food crust deposits are also inconsistent with charred plant material. Therefore, except at one or two sites, our analysis rules out the processing and storage of nut resources as the main use of early pottery in north-eastern North America. This mismatch between the evidence from the analysis of food remains and organic residue data, even accounting for differential preservation, implies that early ceramic containers were used selectively to process aquatic resources rather than opportunistically to process anything and everything that was available in the environment. The small number of Vinette 1 vessels at any one site and the absence of a significant shift in environmental conditions or increased abundance of a particular faunal species in archaeological deposits also suggest that the initial production and use of ceramic containers were not solely linked to some functional demand for new resources or intensified exploitation of existing resources. A more likely explanation is that new social contexts of consumption triggered pottery innovation.

In north-eastern North America the innovation of pottery co-occurred with key social developments such as the increased regionalisation and complexity of hunter-gatherer groups (Versaggi Reference Versaggi1999), the emergence of new elaborate mortuary practices (Farnsworth & Emerson Reference Farnsworth and Emerson1986; Heckenberger et al. Reference Heckenberger, Petersen, Basa, Cowie, Spiess and Stuckenrath1990), and the creation of long-distance interaction networks that ensured the circulation of prestige items (Taché Reference Taché2011). Archaeologically, this is recognised by increased evidence for surplus accumulation (e.g. storage features) and social inequalities (e.g. differential distribution of grave goods), the advent of burial precincts distinct from habitation sites, complex burial practices shared between distinct groups (e.g. cremations, intentional destruction and burning of grave goods, abundance of red ochre in burials), and by the widespread distribution of stylistically and technologically homogeneous artefacts (e.g. Onondaga chert bifaces, ground slate objects) and exotic raw materials (e.g. native copper, marine shells). The social context for such long-distance interaction typically takes place at large, episodic and multi-ethnic gathering sites. So-called ‘trade fairs’ have been ethnographically documented among a diverse range of hunter-fisher-gatherer groups not only in north-eastern North America (Bouchard Reference Bouchard2002) but also in regions as diverse as Alaska, Australia and the American Northwest (Jackson Reference Jackson and Gregg1991). These large social gatherings generally occurred when concentrations of aquatic resources peaked and when surpluses could be produced for exchange.

We suggest that many of the early pottery sites in north-eastern North America were important focal points for such large seasonal gatherings. Now, based on the new molecular evidence, it seems that the invention and widespread uptake of pottery throughout north-eastern North America was associated with the preparation of aquatic resources within this context. Seasonal peaks in either the abundance of migratory fish or marine and freshwater species during spawning are likely to have attracted multiple local bands and promoted cooperative exploitation. Intriguingly however, the relatively small size and low abundance of vessels at these sites precludes a major economic role for pottery. Instead, pottery may have been used to prepare fish as part of small-scale celebratory feasts. The act of cooking and consuming fish with novel ceramic containers would have been largely symbolic, serving to cement social relations during these important periods of aggregation. Therefore, we would expect the bulk of aquatic resources harvested during these gatherings to be processed and consumed using other means.

A related interpretation is that fish oil, a valued exchange commodity among native populations in historical times (Martin Reference Martin1999), was produced during these episodic gatherings and that ceramic containers were used for its preparation. An interesting comparison can be done with eulachon oil (Thaleichthys pacificus), a major source of fat for prehistoric and early historic native communities of coastal British Columbia (Kuhnlein et al. Reference Kuhnlein, Chan, Thompson and Nakai1982). After harvest, the process of rendering oil begins with the ageing of this anadromous fish for one to two weeks in large bins or pits. The ripened fish are then placed into boiling water in a large vat set on a platform with a fire built beneath. The fish are boiled, mashed into small pieces, reboiled and left to simmer for 5 to 12 hours. Eventually, the layer of clear oil is skimmed from the surface to smaller pots and further refined by direct heating to facilitate its long-term storage. If valuable fish oil was processed in a similar manner by early pottery-using communities in north-eastern North America, Vinette 1 pots would have been useful containers for this last processing stage. And as large quantities of fish yield limited amounts of oil, only a few ceramic containers would have been required. The production of fish oil either for exchange with more distant communities, or as a highly valued prestige food for conspicuous consumption, would also reinforce social relations during periodic aggregation of scattered hunter-gatherer groups, in keeping with the ‘cooperative harvesting’ hypothesis.