Thomas Higham

ShCal04 Southern Hemisphere Calibration, 0–11.0 Cal Kyr BP

Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere (super 14) C dates.

Ancient human genome sequence of an extinct Palaeo-Eskimo

We report here the genome sequence of an ancient human. Obtained from ∼4,000-year-old permafrost-preserved hair, the genome represents a male individual from the first known culture to settle in Greenland. Sequenced to an average depth of 20×, we recover 79% of the diploid genome, an amount close to the practical limit of current sequencing technologies. We identify 353,151 high-confidence single-nucleotide polymorphisms (SNPs), of which 6.8% have not been reported previously. We estimate raw read contamination to be no higher than 0.8%. We use functional SNP assessment to assign possible phenotypic characteristics of the individual that belonged to a culture whose location has yielded only trace human remains. We compare the high-confidence SNPs to those of contemporary populations to find the populations most closely related to the individual. This provides evidence for a migration from Siberia into the New World some 5,500 years ago, independent of that giving rise to the modern Native Americans and Inuit.

CURRENT PRETREATMENT METHODS FOR AMS RADIOCARBON DATING AT THE OXFORD RADIOCARBON ACCELERATOR UNIT (ORAU)

In this paper, we summarize the main chemical pretreatment protocols currently used for AMS radiocarbon dating at the Oxford Radiocarbon Accelerator Unit, updating the protocols last described by Hedges et al. (1989).

Improvements to the Pretreatment of Bone at Oxford

Bone is one of the most widely used materials for dating archaeological activity. It is also relatively difficult to pretreat effectively and new methods are an area of active research. The purpose of the chemical pretreatment of bone is to remove contaminants present from burial and to do so in a way which does not add any additional laboratory contaminant. To some extent, these two aims must be balanced since, on the whole, the more complex the procedure and the more steps included, the greater the chance for contamination. At the Oxford Radiocarbon Accelerator Unit (ORAU), the method used is a continuous-flow or manual acid/base/acid (ABA) treatment followed by gelatinization and ultrafiltration (based on Brown et al. [1988]; documented in Bronk Ramsey et al. [2000]). We find this overall method is very effective at removing more recent contamination in old bones. However, two aspects of the method have recently been improved and are reported here: the redesign of ORAUs continuous flow pretreatment and a new protocol in our pretreatment ultrafiltration stage.

Symbolic use of marine shells and mineral pigments by Iberian Neandertals

Two sites of the Neandertal-associated Middle Paleolithic of Iberia, dated to as early as approximately 50,000 years ago, yielded perforated and pigment-stained marine shells. At Cueva de los Aviones, three umbo-perforated valves of Acanthocardia and Glycymeris were found alongside lumps of yellow and red colorants, and residues preserved inside a Spondylus shell consist of a red lepidocrocite base mixed with ground, dark red-to-black fragments of hematite and pyrite. A perforated Pecten shell, painted on its external, white side with an orange mix of goethite and hematite, was abandoned after breakage at Cueva Antón, 60 km inland. Comparable early modern human-associated material from Africa and the Near East is widely accepted as evidence for body ornamentation, implying behavioral modernity. The Iberian finds show that European Neandertals were no different from coeval Africans in this regard, countering genetic/cognitive explanations for the emergence of symbolism and strengthening demographic/social ones.

Population genomics of Bronze Age Eurasia

The Bronze Age of Eurasia (around 3000–1000 BC) was a period of major cultural changes. However, there is debate about whether these changes resulted from the circulation of ideas or from human migrations, potentially also facilitating the spread of languages and certain phenotypic traits. We investigated this by using new, improved methods to sequence low-coverage genomes from 101 ancient humans from across Eurasia. We show that the Bronze Age was a highly dynamic period involving large-scale population migrations and replacements, responsible for shaping major parts of present-day demographic structure in both Europe and Asia. Our findings are consistent with the hypothesized spread of Indo-European languages during the Early Bronze Age. We also demonstrate that light skin pigmentation in Europeans was already present at high frequency in the Bronze Age, but not lactose tolerance, indicating a more recent onset of positive selection on lactose tolerance than previously thought.

82,000-year-old shell beads from North Africa and implications for the origins of modern human behavior

The first appearance of explicitly symbolic objects in the archaeological record marks a fundamental stage in the emergence of modern social behavior in Homo. Ornaments such as shell beads represent some of the earliest objects of this kind. We report on examples of perforated Nassarius gibbosulus shell beads from Grotte des Pigeons (Taforalt, Morocco), North Africa. These marine shells come from archaeological levels dated by luminescence and uranium-series techniques to ≈82,000 years ago. They confirm evidence of similar ornaments from other less well dated sites in North Africa and adjacent areas of southwest Asia. The shells are of the same genus as shell beads from slightly younger levels at Blombos Cave in South Africa. Wear patterns on the shells imply that some of them were suspended, and, as at Blombos, they were covered in red ochre. These findings imply an early distribution of bead-making in Africa and southwest Asia at least 40 millennia before the appearance of similar cultural manifestations in Europe.

Dating the late prehistoric dispersal of Polynesians to New Zealand using the commensal Pacific rat

The pristine island ecosystems of East Polynesia were among the last places on Earth settled by prehistoric people, and their colonization triggered a devastating transformation. Overhunting contributed to widespread faunal extinctions and the decline of marine megafauna, fires destroyed lowland forests, and the introduction of the omnivorous Pacific rat (Rattus exulans) led to a new wave of predation on the biota. East Polynesian islands preserve exceptionally detailed records of the initial prehistoric impacts on highly vulnerable ecosystems, but nearly all such studies are clouded by persistent controversies over the timing of initial human colonization, which has resulted in proposed settlement chronologies varying from ≈200 B.C. to 1000 A.D. or younger. Such differences underpin radically divergent interpretations of human dispersal from West Polynesia and of ecological and social transformation in East Polynesia and ultimately obfuscate the timing and patterns of this process. Using New Zealand as an example, we provide a reliable approach for accurately dating initial human colonization on Pacific islands by radiocarbon dating the arrival of the Pacific rat. Radiocarbon dates on distinctive rat-gnawed seeds and rat bones show that the Pacific rat was introduced to both main islands of New Zealand ≈1280 A.D., a millennium later than previously assumed. This matches with the earliest-dated archaeological sites, human-induced faunal extinctions, and deforestation, implying there was no long period of invisibility in either the archaeological or palaeoecological records.

AMS RADIOCARBON DATING OF ANCIENT BONE USING ULTRAFILTRATION

The Oxford Radiocarbon Accelerator Unit (ORAU) has used an ultrafiltration protocol to further purify gelatin from archaeological bone since 2000. In this paper, the methodology is described, and it is shown that, in many instances, ultrafiltration successfully removes low molecular weight contaminants that less rigorous methods may not. These contaminants can sometimes be of a different radiocarbon age and, unless removed, may produce erroneous determinations, particularly when one is dating bones greater than 2 to 3 half-lives of 14C and the contaminants are of modern age. Results of the redating of bone of Late Middle and Early Upper Paleolithic age from the British Isles and Europe suggest that we may need to look again at the traditional chronology for these periods.

The timing and spatiotemporal patterning of Neanderthal disappearance

The timing of Neanderthal disappearance and the extent to which they overlapped with the earliest incoming anatomically modern humans (AMHs) in Eurasia are key questions in palaeoanthropology. Determining the spatiotemporal relationship between the two populations is crucial if we are to understand the processes, timing and reasons leading to the disappearance of Neanderthals and the likelihood of cultural and genetic exchange. Serious technical challenges, however, have hindered reliable dating of the period, as the radiocarbon method reaches its limit at ∼50,000 years ago. Here we apply improved accelerator mass spectrometry 14C techniques to construct robust chronologies from 40 key Mousterian and Neanderthal archaeological sites, ranging from Russia to Spain. Bayesian age modelling was used to generate probability distribution functions to determine the latest appearance date. We show that the Mousterian ended by 41,030–39,260 calibrated years bp (at 95.4% probability) across Europe. We also demonstrate that succeeding ‘transitional’ archaeological industries, one of which has been linked with Neanderthals (Châtelperronian), end at a similar time. Our data indicate that the disappearance of Neanderthals occurred at different times in different regions. Comparing the data with results obtained from the earliest dated AMH sites in Europe, associated with the Uluzzian technocomplex, allows us to quantify the temporal overlap between the two human groups. The results reveal a significant overlap of 2,600–5,400 years (at 95.4% probability). This has important implications for models seeking to explain the cultural, technological and biological elements involved in the replacement of Neanderthals by AMHs. A mosaic of populations in Europe during the Middle to Upper Palaeolithic transition suggests that there was ample time for the transmission of cultural and symbolic behaviours, as well as possible genetic exchanges, between the two groups.