Paul Szpak | Trent University (original) (raw)

Papers by Paul Szpak

The use of isotopic measurements in archaeological research has increased rapidly over the past ~... more The use of isotopic measurements in archaeological research has increased rapidly over the past ~25 years, owing largely to the proliferation of the instruments required to produce these measurements relatively quickly and cheaply. Unfortunately, the understanding of how to adequately calibrate and report these isotopic data has not kept pace. We surveyed nearly 500 archaeological research papers published within the past 25 years that presented original isotopic data. We found that, generally, the majority of studies do not provide adequate information regarding how isotopic measurements were calibrated, nor how analytical uncertainty (precision and accuracy) was assessed. We review and present recommendations for data analysis, calibration, and reporting to aid archaeological researchers who use isotopic measurements and practices. We present a simple method for quantifying standard analytical uncertainty using data that would be provided by most laboratories.

Lake Ontario once supported a large complex of Atlantic Salmon (Salmo salar) populations that sus... more Lake Ontario once supported a large complex of Atlantic Salmon (Salmo salar) populations that sustainable population of Atlantic Salmon have focused on determining whether Lake Ontario's original salmon populations had migrated to the Atlantic Ocean as part of their lifecycle (anadromy), stayed in the lake year-round (potamodromy), or both. We used stable carbon, nitrogen, and sulfur isotope analyses of archaeological bones and historical museum-archived salmon scales to show that the original salmon populations from Lake Ontario completed their entire lifecycle without migrating to the

RATIONALE: Fish bone collagen isotopic measurements are increasingly important in palaeodietary a... more RATIONALE: Fish bone collagen isotopic measurements are increasingly important in palaeodietary and paleoenvironmental studies yet differences in the chemical and physical properties of fish relative to other vertebrate bones are rarely considered. Lipid content in fish bone, which can exceed 50%, may underlie the poor collagen integrity criteria typically observed in archaeological studies. METHODS: We compare stable carbon and nitrogen isotopic and elemental compositions of bone collagen prepared using four different methods from a wide range of modern fish species to: (1) assess the extent to which lipid content influences bone collagen δ 13 C and δ 15 N values, and (2) evaluate the relative efficacy of chemical (2:1 chloroform/methanol) and physical (30 kDa ultrafilters) methods for removing lipids from bones. RESULTS: Lower δ 13 C values were observed when the lipid content exceeded 5% of the initial bone mass. The lipid content did not influence the δ 15 N values. 30 kDa ultrafiltration, a common pretreatment for purifying archaeological collagen, removed fewer lipids and was associated with reduced collagen yields (37% loss) as well as altered amino acid compositions. In contrast, collagen prepared using a 2:1 chloroform/methanol lipid extraction step resulted in significantly improved collagen yields, elemental compositions, and isotopic measurements relative to a control treatment. CONCLUSIONS: The chemical lipid extraction method (2:1 chloroform/methanol) performed significantly better than the physical lipid extraction method (30 kDa ultrafilters). Given the high quantities of lipids in fish bones we recommend the inclusion of a chemical lipid extraction step when isolating collagen from modern and archaeological fish bones. Copyright

Carbon and nitrogen stable isotope ratios of bone collagen are an established method for dietary ... more Carbon and nitrogen stable isotope ratios of bone collagen are an established method for dietary reconstruction, but this method is limited by the protein preservation. Zinc (Zn) is found in bioapatite and the isotopic compositions of this element constitute a very promising dietary indicator. The extent of fractionation of Zn isotopes in marine environments, however , remains unknown. We report here on the measurement of zinc, carbon and nitrogen isotopes in 47 marine mammals from the archaeological site of Arvik in the Canadian Arctic. We undertook this study to test and demonstrate the utility of Zn isotopes in recent mammal bone minerals as a dietary indicator by comparing them to other isotopic dietary tracers. We found a correlation between δ 66 Zn values and trophic level for most species, with the exception of walruses, which may be caused by their large seasonal movements. δ 6 Zn values can therefore be used as a dietary indicator in marine ecosystems for both modern and recent mammals.

Current Anthropology, Jun 2015

Carbon and nitrogen isotopic compositions of wool textiles from the north (Virú, Early Intermedia... more Carbon and nitrogen isotopic compositions of wool textiles from the north (Virú, Early Intermediate Period) and central (Chancay, Late Intermediate Period) coasts of Peru were used to reconstruct the diet and habitat of the camelids (llamas and alpacas) from which they were produced in order to better understand the regional political economies. The Chancay textiles were derived from camelids primarily raised on high-altitude C3 grasslands. Similarly, isotopic data from Virú textiles assembled in north-coast styles are consistent with the importation of highland camelid wool. For both Virú and Chancay, imported raw materials were crafted in local styles, serving as an effective means of materializing corporate power. Stylistically foreign (noncoastal) Virú textiles were characterized by carbon isotopic compositions similar to those for camelids recovered from Early Intermediate Period sites in the Virú Valley and suggest that these textiles originated in the yungas (1,000–2,300 m asl) or the low sierra (2,300–3,500 m asl). Accordingly, although highland camelid wool was imported to the coast, a simple model of exchange involving the movement of wool textiles exclusively from the puna or the altiplano to the coast is untenable.

Environmental Archaeology, Mar 17, 2015

South American camelids (llamas and alpacas) were of great economic, social and ritual significan... more South American camelids (llamas and alpacas) were of great economic, social and ritual significance in the pre-Hispanic Andes. Although these animals are largely limited to high-altitude (>3500 masl) pastures, it has been hypothesised that camelids were also raised at lower altitudes in the arid coastal river valleys. Previous isotopic studies of Early Intermediate Period (c. 200 BC–AD 600) and Middle Horizon (c. AD 600–1100) camelids support this argument. Here, we utilise carbon and nitrogen isotopic analyses of camelid bone collagen from the Early Horizon (c. 800–200 BC) sites of Caylán and Huambacho on the north-central coast of Peru to examine the management of these animals during the first millennium BC. Most of the camelid isotopic compositions are consistent with the acquisition of animals that were part of caravans, moving between the coast and the highlands. A small number of the animals may have been raised on the coast, suggesting that the practice of coastal camelid husbandry was in the experimental phase during the Early Horizon before growing into a more established practice in the Early Intermediate Period. These results echo zooarchaeological studies from the region that have revealed a paucity of camelid remains in refuse deposits prior to 800 BC, followed by an increase in abundance after 450 BC.

Journal of Anthropological Archaeology, 2014

This study presents carbon and nitrogen isotopic compositions for bone collagen and serially samp... more This study presents carbon and nitrogen isotopic compositions for bone collagen and serially sampled hair from a large collection of South American camelids from two Early Intermediate Period (c. 200 BC to AD 800) sites (Huaca Gallinazo and Huaca Santa Clara) in the Virú Valley (north coast of Peru). The isotopic compositions of these camelids are consistent with plant isotopic compositions from coastal and low altitude settings, but not from high altitude environments, suggesting that at least some of these animals were raised locally. We present several methodological approaches with respect to the treatment of isotopic data from archaeological contexts, outlining quantitative approaches that can provide considerable insight into isotopic variation (within groups, within individuals, between groups, between individuals), as well as temporal variation in isotopic compositions in incrementally growing tissues. We contend that focusing explicitly on variation in animal life histories has the greatest potential with respect to better understanding human–animal interactions in the past. The results demonstrate a large amount of isotopic variability among individuals and an inconsistent amount of within-individual variation, with no consistent shift in the diet leading up to the time of death for a group of animals from a single ritual event. This result suggests that camelid husbandry in the Virú Valley was a small-scale activity, with groups of camelids being managed by families or other small social units. Animals were likely kept primarily in close association to human habitation sites and provided with a diverse array of fodder. These prolonged interactions, occurring at a limited spatial scale, would have allowed a high degree of mutual familiarity to develop between humans and animals. Isotopic compositions for late Middle Horizon (c. AD 1100) sacrificed llamas from Huaca Santa Clara are consistent with Early Intermediate Period camelids, suggesting temporal stability in this small-scale camelid management strategy on the coast, which was fundamentally different from camelid herding in the pastures of the Andean highlands. Isotopic analysis of prehistoric livestock has great potential with respect to better understanding animal husbandry practices and human–animal interactions in the broadest sense because the data provide insight into the ways in which animals lived, rather than the manner in which they died. The variation-centered methodologies outlined in this paper provide a framework with which to approach some of these issues, highlighting the significance of understanding variability in livestock life histories.

Frontiers in Plant Science, Jun 2014

Nitrogen isotopic studies have the potential to shed light on the structure of ancient ecosystems... more Nitrogen isotopic studies have the potential to shed light on the structure of ancient ecosystems, agropastoral regimes, and human-environment interactions. Until relatively recently, however, little attention was paid to the complexities of nitrogen transformations in ancient plant-soil systems and their potential impact on plant and animal tissue nitrogen isotopic compositions. This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions. This paper explores two larger themes that are prominent in archaeological studies using stable nitrogen isotope analysis: (1) agricultural practices (use of animal fertilizers, burning of vegetation or shifting cultivation, and tillage) and (2) animal domestication and husbandry (grazing intensity/stocking rate and the foddering of domestic animals with cultigens). The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems. Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

Journal of Archaeological Science, Feb 20, 2014

Plant nitrogen isotopic compositions are highly variable and are influenced by a diversity of env... more Plant nitrogen isotopic compositions are highly variable and are influenced by a diversity of environmental and anthropogenic factors, including the application of animal-derived fertilizers. Legumes that acquire most of their nitrogen from atmospheric N2 (rather than mineralized soil nitrogen) tend to have relatively low δ15N values (consistently around 0 ‰), and it has been presumed that their δ15N values are largely or wholly unaffected by fertilization. This study presents nitrogen isotopic data from leguminous (garden bean, Phaseolus vulgaris) and non-leguminous (summer squash, Cucurbita pepo) plants subjected to seabird guano fertilization while growing under controlled conditions. Both bean and squash tissue δ15N values were substantially increased by seabird guano fertilization: +16.3 to +19.2 ‰ for bean and +19.6 to +24.5 ‰ for squash. The results of this study demonstrate that the enrichment in plant 15N resulting from seabird guano fertilization occurs consistently in non-maize species. Moreover, it demonstrates that under conditions of high soil nitrogen availability, leguminous plants may obtain a substantial portion of their nitrogen through the uptake of inorganic soil nitrogen (ammonium and nitrate), rather than atmospheric N2. In general, where the δ15N values of fertilizers differ substantially from that of endogenous soil nitrogen and mineralized nitrogen derived from the fertilizer is readily available, a significant manuring effect can be expected in leguminous plants.

Archaeological and Anthropological Sciences, 2013

The maritime fur trade (1785–1840s) led to the local extinction of sea otters (Enhydra lutris) in... more The maritime fur trade (1785–1840s) led to the local extinction of sea otters (Enhydra lutris) in many parts of the northeast Pacific. On the basis of studies of extant sea otter populations, it has been established that they have a disproportionate effect on nearshore ecosystems by limiting sea urchin abundance and facilitating the establishment of nearshore kelp forests; in the absence of sea otters, a local reduction in kelp-derived carbon is therefore expected. We measured the isotopic composition (δ13C and δ15N) of rock- fish (Sebastes spp.) bone collagen from late Holocene ar- chaeological sites in southern Haida Gwaii, BC, Canada, using δ13C as a proxy for kelp-derived carbon in the diet and δ15N as a proxy for trophic position. We observed signifi- cant spatial variability in rockfish kelp-derived carbon (δ13C), but not trophic level (δ15N). Kelp-derived carbon varied largely as a function of site characteristics (wave exposure), suggesting that local oceanographic conditions are important factors with respect to consumer tissue isoto- pic compositions. Kelp-derived carbon decreased in post- European contact rockfish relative to pre-European contact rockfish, likely as a result of the reduction of kelp forests associated with the local extirpation of sea otters. Although we detected a reduction in kelp-derived carbon in rockfish diets, we found no shift in trophic level at sites occupied following the maritime fur trade. This implies a shift in local ecosystems, and particularly in carbon sources, following the maritime fur trade, likely due to a trophic cascade resulting from the local extirpation of sea otters. Stability in rockfish trophic levels, however, implies that rockfish continued to feed at similar trophic levels, consuming prey with similar nitrogen isotopic compositions.

PLoS One, Jan 16, 2013

The development of isotopic baselines for comparison with paleodietary data is crucial, but often... more The development of isotopic baselines for comparison with paleodietary data is crucial, but often overlooked. We review the factors affecting the carbon (δ13C) and nitrogen (δ15N) isotopic compositions of plants, with a special focus on the carbon and nitrogen isotopic compositions of twelve different species of cultivated plants (n = 91) and 139 wild plant species collected in northern Peru. The cultivated plants were collected from nineteen local markets. The mean δ13C value for maize (grain) was −11.8±0.4 ‰ (n = 27). Leguminous cultigens (beans, Andean lupin) were characterized by significantly lower δ15N values and significantly higher %N than non-leguminous cultigens. Wild plants from thirteen sites were collected in the Moche River Valley area between sea level and ~4,000 meters above sea level (masl). These sites were associated with mean annual precipitation ranging from 0 to 710 mm. Plants growing at low altitude sites receiving low amounts of precipitation were characterized by higher δ15N values than plants growing at higher altitudes and receiving higher amounts of precipitation, although this trend dissipated when altitude was >2,000 masl and MAP was >400 mm. For C3 plants, foliar δ13C was positively correlated with altitude and precipitation. This suggests that the influence of altitude may overshadow the influence of water availability on foliar δ13C values at this scale.

Organic fertilizers have the capacity to alter the nitrogen isotopic composition of plants. Camel... more Organic fertilizers have the capacity to alter the nitrogen isotopic composition of plants. Camelid dung and seabird guano are two potentially important fertilizers in the agricultural systems of western South America, particularly Peru and Chile. This paper presents isotopic data (δ13C and δ15N) from field grown plants (maize, Zea mays) fertilized with the following four treatments: CO (control, no fertilizer applied), AS (ammonium sulfate, a chemical fertilizer), DU (camelid dung), and SG (seabird guano). Plants were grown in experimental plots in the Virú Valley, northern Peru. Plants fertilized with the chemical fertilizer presented very similar isotopic compositions compared to the control. Conversely, the camelid dung fertilized plants were characterized by higher δ15N values compared to the control plants (by 1.8 to 4.2‰ depending on the plant part). The seabird guano fertilized plants were greatly enriched in 15N in comparison to the control plants (by 11.3 to 20.0‰). The results of this study have important implications for the reconstruction of human diet using isotopic data derived from bone collagen and related tissues, particularly in the prehispanic Andes, but also in Europe and North America during the 19th century, when Peruvian seabird guano was used extensively. Specifically, the interpretation of the relative contributions of plant and animal protein to the diet on the basis of bulk isotopic compositions of bone collagen (or similar tissues) may be confounded by camelid dung fertilization if the carbon isotopic compositions of the two sources are similar. Likewise, the interpretation of the relative contributions of maize and marine protein may be confounded by seabird guano fertilization.

Background Stable isotope analysis is being utilized with increasing regularity to examine a wide... more Background
Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration) in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (δ15N). Animal excrement is known to impact plant δ15N values, but the effects of seabird guano have not been systematically studied from an agricultural or horticultural standpoint.

Methodology/Principal Findings
This paper presents isotopic (δ13C and δ15N) and vital data for maize (Zea mays) fertilized with Peruvian seabird guano under controlled conditions. The level of 15N enrichment in fertilized plants is very large, with δ15N values ranging between 25.5 and 44.7‰ depending on the tissue and amount of fertilizer applied; comparatively, control plant δ15N values ranged between −0.3 and 5.7‰. Intraplant and temporal variability in δ15N values were large, particularly for the guano-fertilized plants, which can be attributed to changes in the availability of guano-derived N over time, and the reliance of stored vs. absorbed N. Plant δ13C values were not significantly impacted by guano fertilization. High concentrations of seabird guano inhibited maize germination and maize growth. Moreover, high levels of seabird guano greatly impacted the N metabolism of the plants, resulting in significantly higher tissue N content, particularly in the stalk.

Conclusions/Significance
The results presented in this study demonstrate the very large impact of seabird guano on maize δ15N values. The use of seabird guano as a fertilizer can thus be traced using stable isotope analysis in food chemistry applications (certification of organic inputs). Furthermore, the fertilization of maize with seabird guano creates an isotopic signature very similar to a high-trophic level marine resource, which must be considered when interpreting isotopic data from archaeological material.

We examined the isotopic composition (δ13C and δ15N) of sea otter (Enhydra lutris) bone collagen ... more We examined the isotopic composition (δ13C and δ15N) of sea otter (Enhydra lutris) bone collagen from ten late Holocene (ca. 5200 years BP – AD 1900) archaeological sites in northern British Columbia (BC), Canada. Because sea otters are now extinct from much of this region and have not fully re-colonized their former range (e.g. Haida Gwaii and most of northern BC) these data represent an important first step towards better understanding sea otter foraging ecology in BC. The isotopic data suggest a diet composed primarily of benthic invertebrates, with a very low reliance on epibenthic fish. There is very low isotopic and thus inter-individual dietary variability in Holocene BC sea otters during the late Holocene. Furthermore, zooarchaeological abundance data suggest that otters represented a widespread and significant focus of aboriginal hunting practices on the northern BC coast during the mid- to late-Holocene. The consistent reliance on a small number of low trophic level prey and limited dietary variability in Holocene BC sea otters, may reflect top-down impacts on otter populations by aboriginal peoples. As part of our assessment of sea otter diet, we review trophic discrimination factors (Δ13C and Δ15N) for bone collagen from published literature and find marked variability, with mean values of +3.7±1.6 for Δ13C (n = 21) and +3.6±1.3 for Δ15N (n = 15).

Abstract This paper reviews the ultrastructure and chemistry of fish bone, with an emphasis on z... more Abstract
This paper reviews the ultrastructure and chemistry of fish bone, with an emphasis on zooarchaeology and stable isotope analysis. On the basis of the chemical composition of the collagen and the relationships between the collagen and mineral phases, fish bone is more susceptible to biotic and abiotic degradation than mammalian bone and is therefore less likely to be recovered in archaeological deposits. The amino acid composition of fish bone differs from that of mammals (and other taxonomic groups), most notably with respect to hydroxyproline content. The C:N ratio of fish collagen, however, is very similar and slightly lower than mammalian collagen, and thus the traditional range of acceptable C:N ratios for collagen (2.9−3.6) should not be shifted or extended for fish on the basis of the amino acid composition of collagen. An extensive survey of published archaeological bone collagen C:N ratios demonstrates that fish collagen from archaeological contexts tends to have significantly higher C:N ratios than mammalian collagen. The elevated C:N ratios in fish bone collagen may be the result of abiotic degradation processes that occur within the bone after death, the presence of exogenous humic contaminants, or endogenous lipid contaminants."

In this study, we present bone collagen δ13C and δ15N values from a large set of Pleistocene wool... more In this study, we present bone collagen δ13C and δ15N values from a large set of Pleistocene woolly mammoths (Mammuthus primigenius) from Siberia, Alaska and Yukon. Overall, results for mammoth specimens from eastern Beringia (Alaska and Yukon) significantly differ, for both δ13C and δ15N values, from those from western Beringia (northeastern Siberia). In agreement with palynological, entomological, and physiographic data from the same regions, these isotopic differences strongly imply that the `mammoth steppe,' the extensive ice-free region spanning northern Eurasia and northwestern North America, was ecologically variable along its east-west axis to a significant degree. Prior to the Last Glacial Maximum (LGM), the high-latitude portions of Siberia and the Russian Far East appear to have been colder and more arid than central Alaska and Yukon, which were ecologically more diverse. During the LGM itself, however, isotopic signatures of mammoths from eastern Beringia support the argument that this region also experienced an extremely cold and arid climate. In terms of overall temporal trend, Beringia thus went from a condition prior to the LGM of greater ecological variability in the east to one of uniformly cold and dry conditions during the LGM.

Current Anthropology, Jun 2015

Environmental Archaeology, Mar 17, 2015

Journal of Anthropological Archaeology, 2014

Frontiers in Plant Science, Jun 2014

Journal of Archaeological Science, Feb 20, 2014

Archaeological and Anthropological Sciences, 2013

PLoS One, Jan 16, 2013

Economic trends and resource use patterns have long been placed at the root of major social and c... more Economic trends and resource use patterns have long been placed at the root of major social and cultural developments among global societies. Among First Nations societies along the Northwest Coast (NWC) of North America, for example, intensive use of seasonally abundant, storable resources, such as salmon, herring and various shellfish, has been argued to form the basis for the rise of more complex, sedentary societies. Traditional zooarchaeological analyses reveal coarse aspects of faunal use trends across space and time, and as such studies have accumulated on the NWC increasing regional variability has become evident. Identifying the degree of local variability, however, is complicated by the limits of traditional zooarchaeological analysis. On the NWC, key resources, such as salmon and rockfish, can only be morphologically identified to broad, generic taxonomic levels. We have employed the analysis of stable carbon and nitrogen isotopes to gain a more high-resolution understanding of variable use of these and other resources, successfully identifying the use of locally variable sub-populations of diverse taxa. The integration of traditional zooarchaeological and isotopic data can provide a much more nuanced understanding of regional and temporal trends in human economic behavior. This is exemplified in our ongoing research in southern Haida Gwaii, which points to a distinct pattern of local and temporal variability in the use of a wide range of faunal taxa.

This study presents isotopic data for a large number of camelids (~100) recovered from three site... more This study presents isotopic data for a large number of camelids (~100) recovered from three sites (Huaca Gallinazo, Huancaco, and Huaca Santa Clara) in the Viru Valley. These animals are derived from both residential and ceremonial contexts, and date to the Early Intermediate Period and late Middle Horizon. When examined in light of isotopic data collected from a large number of wild plant species along an altitudinal transect in northern Peru, the isotopic data strongly suggest that these animals were raised on local vegetation and not imported from the highlands. Moreover, there is a significant amount of between- and within-individual variation in isotopic composition, suggesting a diversified foddering strategy that may have been the product of small-scale camelid herding.

This paper presents stable isotope data from archaeological South American camelids, as well as t... more This paper presents stable isotope data from archaeological South American camelids, as well as textiles manufactured from camelid wool derived from a variety of contexts (e.g. midden, ceremonial) from the north coast of Peru. The isotopic data suggest an extremely variable, and markedly different pattern of camelid management than has been recorded for modern and ethnohistoric herders in the Peruvian highlands. The implications for these management decisions are assessed in light of recent anthropological literature that has addressed the significant and complex manners in which the lives and deaths of humans and animals influence and are influenced by a multitude of social, economic, and political forces.

This study presents stable isotope (δ15N) data for maize (Zea mays) fertilized with Peruvian seab... more This study presents stable isotope (δ15N) data for maize (Zea mays) fertilized with Peruvian seabird guano and camelid dung; plants were grown under field (agricultural plots in the Virú Valley, Peru) and controlled (growth chamber) conditions. A very large enrichment in 15N characterized both the growth chamber and field grown plants fertilized with seabird guano (> +20‰), while the camelid dung fertilized plants are characterized by a more moderate enrichment in 15N (2 to 5‰), similar to what has been observed for European crops fertilized with livestock manure. We discuss these results in light of the interpretation of human dietary practices in the Andes, as well as the potential of detecting these fertilization practices using various kinds of isotopic data.

A thorough understanding of the taphonomic processes that structure zooarchaeological assemblages... more A thorough understanding of the taphonomic processes that structure zooarchaeological assemblages is essential for their interpretation. From a comparative perspective, this paper reviews the chemical and structural composition of fish bone, and the role that they play in the survival of fish bone in archaeological assemblages. Fish are characterized by several important differences in comparison with other vertebrates, specifically: (1) a less stable organic component, (2) weaker mineral- organic interactions, (3) loosely packed and poorly mineralized collagen, (4) a higher concentration of skeletal lipids. All of these factors make fish bone, in comparison to mammalian or bird bone, more prone to biotic and abiotic degradation in the burial environment.

This study presents stable isotope (δ13C and δ15N) and vital data for maize (Zea mays) fertilized... more This study presents stable isotope (δ13C and δ15N) and vital data for maize (Zea mays) fertilized with Peruvian seabird guano and llama dung; plants were grown under field (agricultural plots near Guañape, Peru) and controlled (growth chamber) conditions. A massive enrichment in 15N characterized both the growth chamber and field grown plants fertilized with seabird guano (>20‰), while the llama dung fertilized plants are characterized by a more moderate enrichment in 15N (~2‰), similar to what has been observed for European crops fertilized with livestock manure. We discuss these results in light of the interpretation of human dietary practices in the Andes, as well as the potential of detecting these fertilization practices using isotopic data. In addition to these isotopic patterns, there are numerous changes in the routing and accumulation of plant metabolites, plant growth and fungal growth that were documented as a result of fertilization. We discuss the implications of these factors with respect to prehispanic agricultural practices in the Andes.

This paper summarizes results from growth chamber and field studies examining the effects of seab... more This paper summarizes results from growth chamber and field studies examining the effects of seabird guano fertilization on the stable isotopic composition of maize. The results are discussed in light of isotopic data obtained from human and animal remains from the Andes. In particular, isotopic data obtained thus far from Moche sites, suggest that seabird guano did not play a significant role as a fertilizer, even though guano-related imagery occurs regularly in Moche material culture, and numerous Moche offerings were recovered from the guano islands in the nineteenth century.

This study presents stable isotope (d15N) data for maize (Zea mays) fertilized with Peruvian seab... more This study presents stable isotope (d15N) data for maize (Zea mays) fertilized with Peruvian seabird guano and llama dung; plants were grown under field (agricultural plots near Guañape, Peru) and controlled (growth chamber) conditions. A very large enrichment in 15N characterized both the growth chamber and field grown plants fertilized with seabird guano (>20‰), while the llama dung fertilized plants are characterized by a more moderate enrichment in 15N (2␣5‰), similar to what has been observed for European crops fertilized with livestock manure. We discuss these results in light of the interpretation of human dietary practices in the Andes, as well as the potential of detecting these fertilization practices using various kinds of isotopic data.

Dietary reconstruction using stable isotopes depends on a thorough understanding of the sources a... more Dietary reconstruction using stable isotopes depends on a thorough understanding of the sources and patterns of isotopic variation in the foods consumed. The potential importance of manured crops has been recognized as a confounding factor in the interpretation of animal protein consumption in Europe due to high plant δ15N values. In the Andes, the practices of fertilization with both llama dung and seabird guano mined from offshore islands is known to have occurred historically, and the high agricultural productivity in regions with low nutrient levels has led some to suggest that the addition of exogenous nitrogen from animal sources was necessary. In the absence of written records, however, the importance these fertilizers have been difficult to determine. This paper presents the results of a series of controlled experiments examining the influence of seabird guano and llama dung on maize. We discuss the implications of this study for the reconstruction of subsistence practices in the prehispanic Andes.

** This presentation was the winner of the 2011 Barbara Lawrence Award for Best Student Paper at the Annual Meeting of the Society for Ethnobiology **

Later published as: Szpak, P., Orchard, T.J., McKechnie, I., Gröcke, D.R., 2012. Historical Ecology of Late Holocene Sea Otters (Enhydra lutris) from Northern British Columbia: Isotopic and Zooarchaeological Perspectives. J. Archaeol. Sci. doi: 10.1016/j.jas.2011.12.006.

Seabird guano from the arid western coast of South America was one of the most widely used fertil... more Seabird guano from the arid western coast of South America was one of the most widely used fertilizers in the nineteenth century, although its importance in prehispanic agricultural systems has been difficult to determine. This paper presents data from a controlled study of maize fertilized with Peruvian seabird guano, outlining the effects of different fertilization regimes on maize growth and isotopic composition (δ13C and δ15N). We discuss the implications of this study for the identification of guano fertilization through isotopic analysis of archaeological materials.

In the absence of written records, the importance of seabird guano as a fertilizer in the prehisp... more In the absence of written records, the importance of seabird guano as a fertilizer in the prehispanic Andes has been difficult to determine. This paper presents the results of a series of controlled experiments with plants (maize, beans and squash) fertilized with Peruvian seabird guano. This study demonstrates a very large (>15‰) enrichment in 15N in guano-fertilized plants, which implies that guano fertilization should be relatively easily detectable through the isotopic analysis of human remains. We discuss the implications of this study for the reconstruction of subsistence practices in the prehispanic Andes.

Without the aid of written records, the relative importance of seabird guano as a fertilizer in t... more Without the aid of written records, the relative importance of seabird guano as a fertilizer in the prehispanic Andes has been difficult to determine. This paper presents data from a controlled experiment of plants (maize, beans and squash) fertilized with Peruvian seabird guano. This study demonstrates a very large (>15‰) enrichment in 15N in guano-fertilized plants, which implies that guano fertilization should be easily detectable through the isotopic analysis of human remains. We discuss the implications of this study for the reconstruction of subsistence practices in the prehispanic Andes.

Sea otters (Enhydra lutris) were once ubiquitous on the Pacific coast of North America until they... more Sea otters (Enhydra lutris) were once ubiquitous on the Pacific coast of North America until they were reduced to the brink of extinction following the maritime fur trade (ca. 1780s – 1830s). Based almost entirely on data from Alaska and California, the role of the sea otter as a ‘keystone species’ in nearshore communities has been discussed extensively. Because the sea otter has yet to be reestablished in much of its former range (particularly in British Columbia, Washington and Oregon) very little is known about the regional variability in sea otter foraging ecology and it is difficult to predict the potential effects of future range expansions on the structuring of nearshore ecosystems and fisheries. In this paper we present isotopic data (δ13C and δ15N of bone collagen) for sea otters from ten Late Holocene archaeological sites in British Columbia. The data demonstrate a high reliance on benthic invertebrates (sea urchins, clams, mussels) and a surprising lack of dietary variability given the wide range of potential sea otter prey items. Some animals from fur trade era deposits also display divergent δ13C values, suggesting that either (1) significant changes had occurred to nearshore ecosystems prior to the complete removal of sea otters, or (2) these animals were acquired through trade. We discuss both of these possibilities in light of isotopic data from other nearshore species (epibenthic fish) from the same archaeological contexts.

Although camelids (llamas and alpacas) were extremely important in every facet of prehispanic And... more Although camelids (llamas and alpacas) were extremely important in every facet of prehispanic Andean economies, very little is known about how these animals were managed. This paper reconstructs camelid management practices and aspects of political economy in the Virú Valley of northern Peru during the Early Intermediate Period (200 BC – 800 AD) through stable isotope (δ13C and δ15N) analysis of multiple tissues (camelid bone collagen, hair and nail keratin) and textiles spun from camelid fibre from the same archaeological contexts. The data provide evidence for diverse foddering practices characterized by much more dietary variability than exists for either modern or prehistoric highland camelids. Many of these animals consumed large quantities of maize that was likely fertilized with either camelid dung or seabird guano. Isotopic compositions of textiles that exhibit local weaving structure and iconography differ markedly from the animals in the midden deposits, supporting the notion that these fabrics were composed of wool from non-local animals. We conclude by discussing the political and domestic economy in the Virú polity during the Early Intermediate Period with a particular emphasis on traded wool and textiles.

This paper presents stable isotope (δ13C and δ15N) data for textiles composed of camelid fibre (h... more This paper presents stable isotope (δ13C and δ15N) data for textiles composed of camelid fibre (hair keratin) and butchered camelid remains (bone collagen) from two Early Intermediate period occupations in the Virú Valley of northern Peru: Huaca Santa Clara (V-67), a mid-sized regional administrative centre, and the Gallinazo Group, though to be the capital of the Virú polity. There are marked differences in the stable carbon and nitrogen isotope composition of textiles vs. camelid bone collagen from the same contexts. Additionally, there is a positive correlation between δ13C and δ15N for bone collagen, but not for textiles. This strongly suggests not only that the textiles were composed of wool from non-local animals and that there were significant differences in the diet, habitat and management practices of the animals used as fibre producers, and those that ended up in the midden deposits.

Over the last two decades, the knowledge about the divergence of the different lineages within Pl... more Over the last two decades, the knowledge about the divergence of the different lineages within Plio-/Pleistocene mammoths has seen major upheavals. Our understanding of a steady transformation within a mere chronospecies has been shaken by the re-assessment of paleontological evidence depicting the evolution of mammoths as a series of divergence events, implying a mosaic of contemporaneous groups at different evolutionary stages. Not only can we observe the general patterns of structural accentuation in mammoth cranio-dental features in temporally distinct stages, but also in contemporaneous, geographically separated lineages. Supplementing the anatomical evidence, recent genetic research on Late Pleistocene mammoths (implementing ancient DNA phylogeography and genomic studies) has sparked its own set of controversies. These offer contrasting models of the regional and temporal origins of the observed diversity in these populations.
However, a reassessment of the total evidence –including new genetic results– yields congruence between molecular and paleontological theories on mammoth history, emphasizing the once claimed and little realized goal of ancient DNA studies. On the structure and timing of mammoth evolution, this assessment resolves what may have once been seen as an inevitable collapse or collision between divergent theories.

Vegetation History and Archaeobotany, 2019

Isotopic measurements of plant remains from archaeological sites are now routinely used to recons... more Isotopic measurements of plant remains from archaeological sites are now routinely used to reconstruct agricultural practices in the Old World. These studies use charred botanical remains as the analytical substrate because (1) these are the materials that are commonly preserved in the archaeological record and (2) the integrity of the isotopic compositions of archaeological plant remains that are uncharred or desiccated has been questioned, particularly for δ15N. By comparing charred and uncharred plant remains from two Late Moche (AD 600–800) sites in the Jequetepeque valley on the north coast of Peru—San José de Moro and Cerro Chepén—we sought to directly test the assumption that the isotopic compositions of desiccated plant remains are not representative of the isotopic compositions of the living plants. The average δ15N values of charred (+11.3 ± 4.4‰) and desiccated (+10.1 ± 5.1‰) remains from these two sites did not significantly differ from one another, suggesting that uncharred plant remains can produce reliable isotopic measurements under some circumstances. Furthermore, the relatively high δ15N values of the plant remains from these two sites are consistent with the ancient use of composted camelid manure as a fertilizer.