The geochronological potential of isoleucine epimerisation in cassowary and megapode eggshells from archaeological sites

Our research demonstrates that the extent of isoleucine epimerisation (A/I) in fragments of avian eggshells provides geochronological information in archaeological contexts. In the archaeological sequence of Hay Cave, northern Queensland, Australia, there is an excellent correspondence between the A/I values of Australian brush-turkey (Alectura lathami) eggshells (n = 99) and independent geochronological control (n = 16 radiocarbon ages including 4 on eggshell calcite). The A/I values identify three phases of deposition during the Holocene at Hay Cave. In contrast to the Alectura eggshell A/I values, a poor correspondence was observed between the A/I values of cassowary (Casuarius) eggshells from Toé (n = 35) and Kria caves (n = 23) (Ayamaru Plateau, Papua) and the depths from which the specimens were recovered in these stratified sequences. Given coherent archaeofauna trends and radiocarbon chronologies (n = 8 and 2 eggshell calcite radiocarbon ages at Toé and Kria, respectively) with respect to depth, the variable A/I values are not explicable in terms of mixing. Rather, the variability is most likely due to exposure of the eggshells to the high temperatures of campfires. Despite the variability, eggshells with relatively low A/I values amongst specimens recovered from similar depths (and therefore presumably least influenced by high temperatures) exhibit a gradual increase in A/I with respect to depth, as expected in a stratified deposit. From this observation it is suggested that the identification of heated eggshells will increase confidence in geochronological information provided by A/I. These studies illustrate the complications that arise from campfire-induced acceleration of amino acid racemisation and emphasise that although this phenomenon is common, it is not universally encountered in archaeological contexts.     

Stable isotope evidence of human diet at the Nukdo shell midden site,South Korea

Carbon and nitrogen stable isotope analysis was undertaken on bone collagen extracted from archaeological human (n = 48) and animal (n = 45) skeletons from the Nukdo site, Location I C, South Korea. This shell midden and grave site is dated from the late Mumun (550–300 BC) to early Iron Age (300 BC-1 AD) periods. The herbivorous mammals fell within the range of C₃ consumers, with average values of δ¹³C = −21.0 ± 0.5‰ and δ¹⁵N = 3.6 ± 0.5‰ for deer (n = 16) and δ¹³C = −20.6 ± 0.5‰ and δ¹⁵N = 4.5 ± 2.0‰ for wild boar (n = 17). Humans from this site averaged δ¹³C = −18.3 ± 0.4‰ and δ¹⁵N = 11.2 ± 0.7‰ for adults (n = 15) and δ¹³C = −18.7 ± 0.7‰ and δ¹⁵N = 12.5 ± 1.1‰ for juveniles (n = 33). These δ¹³C values indicate that there was no significant input of C₄ plants in the human diets and this may be associated with the spread of rice agriculture in the Mumun period. Human bone collagen δ¹³C and δ¹⁵N values indicate that there was some consumption of marine foods, although the main protein sources were from terrestrial foods. The isotope data demonstrate that the humans at Nukdo had mixed diets that included marine and terrestrial protein, including C₃ plants such as rice. Finally, the isotope results from the juveniles indicate that weaning occurred before the age of 1.5 years in this period.     

Critical reassessment of putative Acheulean Porosphaera globularis beads

Excavations at Acheulean sites in northern Europe at the end of the 19th century have yielded fossil sponges belonging to the Late Cretaceous species Porosphaera globularis. The spherical morphology of these fossils, their small size, and the presence of a natural complete perforation in their center have led some archaeologists to interpret them as the oldest known beads. Others argue that the presence of these fossils at archaeological sites is due to natural processes. Re-examination of material collected during the 19th century has recently revived the bead interpretation. We tested the bead hypothesis by analyzing 13 samples of Porosphaera from nine sites in Britain and France. We conducted morphometric and microscopic analyses on specimens recovered from archaeological sites (n = 349), a natural geological sample, which was collected directly from Cretaceous strata (n = 352), and a sample from a Bronze Age burial (n = 43). Reappraisal of contextual data shows that the association of these finds with Acheulean artifacts is uncertain. Our results show that archaeological specimens are significantly different in size and perforation pattern from those of the natural geological sample. This may be due to size-sorting caused by sedimentary processes, size-selection by Palaeolithic people or by 19th century collectors. Modifications of the fossils' natural shape were detected on a few specimens in the form of localized abrasions and microchipping along the hole margins. A single specimen displays a facet close to the hole produced by grinding. The surfaces of these features exhibit a hue lighter than that observed on the remainder of the specimens indicating that they may be recent in origin and due to post-excavation and preservation treatment. However, this seems contradicted, for some specimens from Bedford, by the fact that according to Smith, W.G. [1884. On a Palaeolithic floor at North-East London. Journal of the Anthropological Institute of Great Britain and Ireland 13, 357–384] the specimens bearing microchipping and abrasions were found by him and “not touched or manipulated by the workmen”. We conclude that new excavations of these sites, involving systematic screening of sediments, are needed in order to attempt to solve the Porosphaera “mystery”.     

Stable isotopes and diet at Ancient Kerma,Upper Nubia (Sudan)

Carbon and nitrogen stable isotope values were measured from bone collagen extracted from archaeological Nubian human (n = 54) and faunal (n = 61) populations from the site of Kerma, Sudan. Collagen suitable for isotopic analysis was extracted from 22 faunal and 48 human samples from the Eastern cemetery site, dated to the Middle Kerma (c. 2050–1750 BC) and Classic Kerma (c. 1750–1500 BC) periods respectively. The isotopic data indicate that the human dietary regimen included a mix of C₃ and C₄ plant-derived components, with a larger C₄ component than previously reported in archaeological Egyptian Nile Valley populations. Elevated δ¹⁵N values are attributed to consumption of dietary resources from a ¹⁵N-enriched terrestrial ecosystem. The faunal isotope data also indicate the consumption of C₃ and C₄ plants. The large range of δ¹³C values measured in both the human and faunal samples supports previous work suggesting that a significant portion of the populations buried at Kerma may have originated elsewhere, further confirming the Nile Valley as a major corridor for population movement in the region.     

A pilot study into the effects of X-ray and computed tomography exposure on the amplification of DNA from bone

This research investigates the intersection of radiography and aDNA, two commonly used methods in bioarchaeology. The goal of this project was to investigate the effects of radiation on the ability to amplify DNA from bone. Bones (n = 124) from domestic pig (Sus scrofa) feet were randomly sorted into a control group and four treatment groups: (1) single exposure X-ray; (2) single exposure CT; (3) multiple exposures X-ray; and (4) multiple exposures CT. Number of PCR cycles required to amplify DNA in 100 bp, 200 bp and 400 bp segments were used as a proxy for the amount of available DNA. In the 200 bp CT sample, distal phalanges required significantly more amplification cycles than did the other bones and were removed from analysis. Results suggest that in general radiation exposure fragments DNA thereby decreasing the amount that is amplifiable. While these results are suggestive, further research is required to elucidate the degree to which radiation fragments DNA in archaeological specimens.     

Identification of the first reported Lapita cremation in the Pacific Islands using archaeological,forensic and contemporary burning evidence

Burnt human remains excavated from a scoop feature from a cemetery at Teouma, Vanuatu in the western Pacific (∼2850 BP) were examined to assess the nature of the deposit. Possible scenarios explaining the reason the bone was burnt and interred were assessed using osteological signatures taken from archaeological, experimental, and forensic studies. The methodology of the study included recording color change, types of bone distortion, and element representation in conjunction with archaeological evidence. The burnt and fragmented human bone (n = 430, fragments weighing 620 g) represents a single adult individual. Macroscopic evidence from the bone indicates the body had been fleshed or fresh at the time of burning and element representation follows a similar pattern to other burials excavated from the site. Excluding burning, there was no evidence of human modification to the bone such as cut marks, percussion pits or peri mortem trauma suggestive of cannibalism. The archaeological evidence from the site indicates that the body had not been burnt in the place the remains were subsequently discovered. The combined macroscopic and archaeological evidence strongly suggests that the human bone was burnt as a result of a deliberate cremation of an individual. If a conclusion of deliberate cremation is accepted, this research represents the first case of a Lapita period cremation and demonstrates how a combination of methods can explain the nature of an archaeological deposit of burnt human bone when the cause is not otherwise apparent.     

Examining dispersal mechanisms for the translocation of chicken (Gallus gallus) from Polynesia to South America

DNA sequencing and radiocarbon dates from the archaeological site of El Arenal-1 (Arauco Peninsula, south central Chile) suggest that Polynesians may have introduced chicken (Gallus gallus) to South America prehistorically (A.D. 1300–1420). The Chilean specimen identified has the exact same amplified mtDNA pattern as samples recovered from archaeological sites in Samoa and Tonga, but is only one base different from prehistoric chicken samples from Tonga (n = 1), Niue (n = 1), Easter Island (n = 1 of 6), and Hawai'i (n = 1). To examine the possible dispersal mechanisms of chicken between Polynesian islands and the Americas, we conducted computer simulations of seafaring from these six island groups and the Tuamotus, as well as return voyages. Simulation results from sailed vessels suggest that in certain months, landfall on the Pacific Coast of South America from Samoa and Tonga was fairly successful at around 40% (particularly in March for the former and January/February for the latter). For Niue, sailed vessels were 21% successful in January with only 2% success in December. Sailed vessels from the Tuamotus (a proxy for closer island groups to the west with evidence for chicken such as the Cook Islands) were successful in January and December, with 15% and 23% of the vessels making landfall in South America. Vessels sailing from all simulations heading east from Easter Island resulted in landfall. Hawai'i had only a 1% success rate if sailing in January, but high numbers of vessels reached southern Mexico and Central America in August and September. Most landfalls occurred much farther north than Chile, in Ecuador and Peru. Unsuccessful voyages from all of the islands other than Easter Island and Hawai'i often made landfall on islands to the east. Return voyages from Chile were not possible or extremely rare during most times of the year. Overall, seafaring simulations suggest that Polynesians may not have initially landed in close proximity to El Arenal-1—contemporaneous or even earlier archaeological evidence of translocated chicken remains may indeed be found further north. In addition, if Polynesians found it difficult or impossible to return to their homeland, the possibility exists that co-mingling between Polynesians and South American groups resulted in offspring that carried an admixture of genetic traits.     

Identifying sword marks on bone: criteria for distinguishing between cut marks made by different classes of bladed weapons

Swords have been one of the major weapons used in violent conflicts for much of human history. Certain archaeological situations, especially those dealing with the recovery and analysis of battle casualties, may raise questions about what type(s) of bladed weapon was used in a particular conflict (e.g., the battle of Kamakura, Japan, AD 1333; the battle of Wisby, Sweden, AD 1361; the battle of Towton, England, AD 1461). Little work has been done, however, on developing criteria to differentiate sword cut marks from other types of cut marks, or to distinguish between marks created by different sword types. To develop such criteria, bovine tibiae (n = 7) were struck using six different types of bladed weapon and the resulting marks (n = 92) were analyzed. Eight traits describing the morphology of the cut mark – such as shape, the presence and unilateral/bilateral state of flaking and feathering, the presence of bone shards, associated breaks, etc. – are defined and related to blade type used. Sword marks were found to be easily distinguishable from knife marks. The variation in marks made by different sword types is significantly correlated with differences in blade weight (p < 0.0001), grip (p < 0.0113), and sharpness (p ≤ 0.0179). The criteria and analyses developed and implemented in this study will be of use to researchers in forensics and osteoarchaeology who want to infer bladed weapon type from marks on bones.     

Migration and Viking Dublin: paleomobility and paleodiet through isotopic analyses

During the early medieval period in Ireland, Dublin was established as the largest Viking settlement on the island in the ninth century AD. A previous biodistance study has suggested that the population of the town consisted of a polyethnic amalgam of immigrant and indigenous. In this study, we use biogeochemistry to investigate paleomobility and paleodiet in archeological human remains from the ninth to eleventh century levels at the sites at Fishamble Street II (National Museum of Ireland excavation number E172), Fishamble Street III (E190) and John’s Lane (E173), as well as twelfth-century remains from Wood Quay (E132). Through radiogenic strontium isotope, stable oxygen, carbon, and nitrogen isotope, and elemental concentration analyses, we investigate the origins of the individuals who lived and died in early and late Viking Dublin. Mean archaeological human enamel and bone isotope values from Dublin are ⁸⁷Sr/⁸⁶Sr = 0.70975 ± 0.00139 (2σ, n = 22), δ¹³C_{carbonate(V-PDB)} = −14.8‰ ± 0.8‰ (1σ, n = 12), and δ¹⁸O_{carbonate(V-PDB)} = −7.2‰ ± 1.0‰ (1σ, n = 12). Archaeological human bone samples exhibit mean δ¹³C_{collagen(V-PDB)} = −20.8‰ ± 0.5‰ (1σ, n = 12) and mean δ¹⁵N_{collagen(AIR)} = +10.0‰ ± 1.7‰ (1σ, n = 12). Comparing these data with archaeological faunal data from Dublin and published data from northern Europe, we argue that there are no clear immigrants from other parts of the North Atlantic, although there is one clear outlier in both origins and diet. Overall, the relative homogeneity in both paleomobility and paleodiet may support models of acculturation in Viking Dublin, rather than a high number of first-generation immigrants or continued migration from Scandinavia.     

Stable isotope palaeodietary study of humans and fauna from the multi-period (Iron Age,Viking and Late Medieval) site of Newark Bay,Orkney

We report here on stable carbon and nitrogen isotope measurements of human and faunal bone collagen from the Iron Age, Viking Age, and Late Medieval site of Newark Bay, Orkney, Scotland. We found a wide range of results for humans in both δ¹³C (−15.4‰ to −20.3‰) and δ¹⁵N (8.6‰–15.6‰) values. The enriched carbon and nitrogen values indicate the consumption of significant amounts of marine protein, which is very unusual for post-Mesolithic (e.g. 4000 cal BC) UK and European populations. Also of interest is a statistically significant difference in δ¹³C (t = −2.48, p = 0.011) and δ¹⁵N (t = −2.44, p = 0.011) values, and therefore diets, between adult males and females at this site, with males (δ¹³C = −17.8 ± 1.2‰, δ¹⁵N = 13.2 ± 1.6‰) having, on average, a higher proportion of marine protein than females (δ¹³C = −18.9 ± 1.1‰, δ¹⁵N = 11.8 ± 1.8‰). The weaning age of the sub-adults was difficult to interpret due to the large isotopic variation in the adult females, but nearly all individuals between birth and 1.25 years have elevated δ¹⁵N values indicating that they were breastfed to some extent.     

Provisioning Inka feasts at Tiwanaku, Bolivia: the geographic origins of camelids in the Pumapunku complex

While political integration can be achieved by many means, here we focus on the use of feasting and statecraft in the Inka Empire of the Andean Late Horizon (c. AD 1400-1532) in South America. In order to examine Inka political integration of the Lake Titicaca Basin of Bolivia, we examine paleomobility and paleodiet through radiogenic strontium and stable oxygen and carbon isotope data in archaeological camelid remains from the site of Tiwanaku. Mean radiogenic strontium isotope values from all archaeological camelid enamel and bone samples is ⁸⁷Sr/⁸⁶Sr = 0.70998 ± 0.00179 (1σ, n = 48), mean stable oxygen isotope values from a sub-set of archaeological camelid enamel and bone samples is δ¹⁸O_{carbonate (VPDB)} = −10.0‰ ± 2.6‰ (1σ, n = 18) and mean stable carbon isotope values from a sub-set of archaeological camelid enamel and bone samples is δ¹³C_{carbonate (VPDB)} = −9.0‰ ± 1.7‰ (1σ, n = 18). While many camelids consumed in these feasting events were likely local to the Lake Titicaca Basin, others came from a variety of different geologic zones, elucidating our understanding of Inka statecraft and the role of feasting in political integration in empires in the past.     

Short-chain n-alkanes (C16–20) in ancient soil are useful molecular markers for prehistoric biomass burning

The incorporation of plant biomass into soil usually leads to long-chain n-alkanes with a relative predominance of odd carbon numbered homologues. Contrastingly, an increase in short-chain even carbon numbered n-alkanes was found in charred biomass with progressing temperatures. We applied lipid analysis to buried ancient topsoils that contained charred organic matter and to corresponding control soils, which were characterized by a lighter color and lower contents of charred materials. Commonly, the proportion of lipid extracts was found to be lower in the ancient soil than in the control samples, which indicated an enhanced degradation of organic matter, e.g., by thermal degradation. All samples displayed a particular pattern of short-chain and even carbon numbered n-alkanes (maximum at n-C₁₆ or n-C₁₈). The ratios CPI (carbon preference index) and ACL (average chain length) for the investigated soil samples matched the ratios found for maize and rye straw charred at 400 °C or 500 °C, respectively. These molecular ratios indicate the presence of charred biomass. The predominance of short-chain and even carbon numbered n-alkanes was a result of thermal degradation of biomass. The degradation products were preserved in ancient soils and could be applied as molecular markers in archaeological or palaeoenvironmental research.     

Frogs as a part of the Eneolithic diet. Archaeozoological records from the Czech Republic (Kutná Hora-Denemark site, Řivnáč Culture)

Within the site of Kutná Hora-Denemark (Kutná Hora distr., central Bohemia – Eneolithic, ?ivná? Culture, 3000–2800 BC), 893 frog bones or bone fragments were present in five archaeological features. All identified specimens are of the Common Frog (Rana temporaria Linnaeus, 1758). Males predominate, according to humeral morphology, and only adult individuals are present. The most important findings come from feature 36, where an accumulation of 739 frog bones (MNI = 123) were found, of which 10% (NISP) were burned. This and other contextual evidence indicates that they relate to activity of the Eneolithic people in the settlement. The predominance of hind leg bones and other circumstantial evidence suggest that the frogs were part of the human diet. Behavioural studies of this species suggest that the frogs were gathered from small ponds during the months of March or April. Similar findings are rare.     

Quantitative computerized tomography for the diagnosis of osteopenia in prehistoric skeletal remains

In this study, we examine the value of bone density assessed by computed tomography (QCT) of the right tibia in the diagnosis of low bone mass in prehistoric bones. Trabecular bone mass (TBM) was assessed by histomorphometry in undecalcified bone sections of a small part of the proximal epiphysis of the right tibia of 78 prehispanic individuals. Bone density was also assessed in the proximal epiphysis of the right tibia, in an area of cancellous bone immediately adjacent to the wedge which was destined to histomorphometry, with the aid of a Tomoscan 60 TX™ (Philipps Medical System, Eindhoven, The Netherlands) using a phantom of hydroxyapatite included in plastic resin at three known concentrations (50, 100 and 200 mg/cc) and ethanol as fat equivalent. Bone density (as bone hydroxyapatite concentration in milligram per cubic centimeter) was calculated by means of a specific software tool (QCT Bone Mineral Analysis System, Image Analysis, California). We compared bone density assessed with QCT with TBM in these individuals, and also, with the results obtained from a modern control group. We calculated the median TBM of the prehispanic sample and tested the sensitivity, specificity, and overall accuracy of QCT in diagnosing TBM values below the median. We later performed the same analyses on 24 more prehispanic individuals. Both QCT (t = 5.61, p < 0.001) and TBM (t = 3.79, p < 0.001) were significantly lower among the prehispanic individuals than among the control ones. QCT showed a significant relationship with TBM (r = 0.41, p < 0.001). QCT values below 100 mg/cc serve to establish a diagnosis of low TBM values with a sensitivity of 82.1% and a specificity of 41%. In the test group sensitivity was 83.3% and specificity, 50%.     

Spatial variation of biologically available strontium isotopes (Sr/Sr) in an archipelagic setting: a case study from the Caribbean

This paper presents the results of strontium (Sr) isotope analysis of modern and archaeological animal remains and modern plant samples from the Caribbean region. The goal is to assess if patterns of human mobility can be determined from the archaeological record in an archipelagic setting. The range of variability and spatial distribution of biologically available strontium isotope signatures is reported and data evaluated to determine if sufficient heterogeneity exists to permit the identification of mobility despite the presence of potentially large contributions of marine strontium in island and coastal ecosystems. The (is)landscape is divided into several sub-regions based on the age and lithology of underlying geology and the variability of ⁸⁷Sr/⁸⁶Sr ratios is reported as; mean ⁸⁷Sr/⁸⁶Sr ± 2 standard deviations, number of samples: 1) Volcanic and Intrusive rocks (0.7077 ± 0.0019; n = 162); 2) Cretaceous–Miocene Limestone (0.7085 ± 0.0009; n = 50); 3) Pliocene–Quaternary Limestone (0.7091 ± 0.0004; n = 54); 4) Sedimentary Deposits (0.7094 ± 0.0015; n = 16); 5) Metamorphic Deposits (0.7104 ± 0.0014; n = 6). There are substantial differences between expected ⁸⁷Sr/⁸⁶Sr values based on associated geology and measured ⁸⁷Sr/⁸⁶Sr in flora and fauna samples. These differences emphasize the importance of focusing on bioavailable strontium, as opposed to geological proxies, for estimations of Sr isotope ranges, especially in archipelagic environments. While some overlap exists between the ⁸⁷Sr/⁸⁶Sr ranges of certain sub-regions, other sub-regions possessed limited variation and could be distinguished based on strontium isotope data. This spatial patterning of biologically available strontium indicates that strontium isotope analyses can be successfully applied to the archaeological study of human mobility within the Caribbean region.     

Examining histology to identify burned bone

Early research suggests that examination of the microscopic internal structure is a valid method for distinguishing burned from unburned bone in the archaeological record. This study compares burned and unburned modern bones with archaeological bones from Sibudu Cave (ca. 60,000 years ago) and Cave of Hearths (over 200,000 years ago) to more fully describe the heat-induced histological changes to bone. We also explore the effects of diagenesis on those changes to determine if histological evidence of burning preserves through fossilisation and diagenetic processes and can be successfully used to identify ancient burning. Application of this technique can help in addressing various issues, including the origins of controlled use of fire and understanding animal butchery and disposal.     

Residential mobility and social identity in the periphery: strontium isotope analysis of archaeological tooth enamel from southeastern Arabia

Strontium isotope analysis represents an effective means of assessing mobility and reconstructing geographic residence patterns in archaeological populations. This biogeochemical technique was utilized to test the hypothesis that burgeoning interregional exchange networks and the occurrence of exotic grave goods in local tombs would correspond with a highly mobile population and a considerable immigrant presence during the Umm an-Nar (2700–2000 BC) period in the UAE. This region has been considered peripheral relative to larger civilizations in Mesopotamia and the Indus Valley, but played an important role as a major supplier of copper for the Persian Gulf. Individuals (n = 100) from six monumental Umm an-Nar tombs (Mowaihat; Tell Abraq; Umm an-Nar Island I, II, V; Unar 1) were selected to evaluate the geographic origins of tomb members. Mean ⁸⁷Sr/⁸⁶Sr ratios from local individuals interred at Mowaihat (0.708863 ± 0.000014; 1σ, n = 12), Tell Abraq (0.708873 ± 0.000020; 1σ, n = 27), Umm an-Nar Island (0.708902 ± 0.000079; 1σ, n = 33), and Unar 1 (0.708805 ± 0.000065; 1σ, n = 25) all display little isotopic variability, indicative of a population that was not highly mobile. However, coupled with archaeological evidence, three immigrants from Tell Abraq (n = 2) and Mowaihat (n = 1) identified by deviant strontium values suggest that this region was actively engaged in interregional interaction. Despite claims that these tombs acted as visible markers of territoriality legitimized by local ancestors buried within them, the presence of non-locals suggests that as commerce became increasingly important, definitions of kinship and social identity may have become more flexible to better meet the needs of the local community and those with whom they interacted.     

Estimation of Age,Growth and Fishing Season of a Palaeolithic Population of Grayling (Thymallus thymallus) Using Scale Analysis

The fish remains sampled from archaeological sites are generally the result of human food refuse; therefore, the study of retrieved fish scales may provide reliable information on the season of capture and on paleoclimate and paleoenvironmental changes. Among Western European freshwater fishes, the grayling, Thymallus thymallus ¸ has the most easily recognizable scales and is a commonly recovered species from Palaeolithic contexts. This study, therefore, is based on the growth pattern analysis of modern and archaeological scales from grayling specimens. The modern specimens were collected monthly in France (n  = 22), Switzerland (n  = 16), Finland (n  = 20) and Sweden (n  = 10). Scale growth patterns were measured using numerical analysis to a high accuracy. The results showed that the archaeological population of grayling is closer to the present Finnish population. Furthermore, the comparison of seasonal growth patterns between current and archaeological European populations demonstrated that graylings were normally captured during the spring at Le Taillis des Coteaux Magdalenian site. This type of approach can be used to understand environmental conditions at a low spatial scale and also to help identify fishing seasons during archaeological periods. Copyright © 2017 John Wiley & Sons, Ltd.     

The use of summed radiocarbon probability distributions in archaeology: a review of methods

Using a database of Australian archaeological radiocarbon dates (n = 2996), this paper explores three key methodological issues associated with the use of summed probability plots of radiocarbon data: 1) the minimum sample size needed for a statistically reliable plot; 2) the effect of radiocarbon calibration on the structure of these plots; and 3) the application of a taphonomic correction to such time-series data. The results identify several protocols, recommended as best-practice when using summed probability plots: 1) a minimum sample size of 500 radiocarbon dates should be used, and the sample size and the mean of the standard deviations of the radiocarbon dates (ΔT) in the sample should both be reported; 2) a moving average trendline of 500-800 years should be used to offset the effects of the calibration process; and 3) Surovell et al. “Correcting temporal frequency distributions for taphonomic bias” [Journal of Archaeological Science 36 (2009) 1715-1724] is explored, with modifications and temporal limits (<25,000 cal years BP) proposed. Correction of time-series data using theoretical taphonomic correction curves is useful as a heuristic tool but can obscure real trends if applied routinely. Comparison between summed probability plots and other occupation data is presented and shows good correlation. However it is recommended that plots are supplemented by other archaeological indices and the cross-comparison of such multiple proxies will strengthen identification of occupation trends.