Prof Christopher Ramsey

Abstract:

AbstractDespite the rich array of perishables Julian Steward (1937) recovered during his 1930s excavations, the Promontory Cave assemblages were dated in relative terms with just a handful of radiocarbon assays until recently. Yet Promontory Caves 1 and 2 are the type sites from which the Promontory Culture was defined, and these assemblages have a critical bearing on our conception of three significant issues in western North American prehistory: the terminal Fremont transition, Numic expansion, and the potential presence of migrating ancestral Apachean populations. To better fix the age of the Promontory Phase, we have undertaken an additional 45 AMS determinations for Promontory perishables. Because of a research focus concerning Promontory footwear, most age estimates come from moccasins, but we have also dated gaming pieces, a bow, an arrow, netting, basketry, matting, and cordage. With the exception of a winnowing basket fragment and some ceramic residue dates, all Promontory Phase assays are tightly focused in an interval running from 662 to 826 radiocarbon years before present (a calibrated 2s range spanning A.D. 1166–1391). Bayesian analyses of the Cave 1 and 2 Promontory Phase perishables suggest that this late period occupation comprised one or two human generations, centering on the interval running from ca. A.D. 1250–1290.

Abstract:

Research on global ice-volume changes during Pleistocene glacial cycles is hindered by a lack of detailed sea-level records for time intervals older than the last interglacial. Here we present the first robustly dated, continuous and highly resolved records of Red Sea sea level and rates of sea-level change over the last 500,000 years, based on tight synchronization to an Asian monsoon record. We observe maximum 'natural' (pre-anthropogenic forcing) sea-level rise rates below 2 m per century following periods with up to twice present-day ice volumes, and substantially higher rise rates for greater ice volumes. We also find that maximum sea-level rise rates were attained within 2 kyr of the onset of deglaciations, for 85% of such events. Finally, multivariate regressions of orbital parameters, sea-level and monsoon records suggest that major meltwater pulses account for millennial-scale variability and insolation-lagged responses in Asian monsoon records.

Abstract:

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 palaeoanthropology1,2. 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 ago3. 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)4, 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 technocomplex5, 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.