The vessel has a height of 29 cm. Both the interior and exterior surfaces were impressed, possibly with cordage 7. Location of Yuchanyan Cave in China Inset and excavation grid showing locations of ceramics arrows: Uncalibrated and calibrated radiocarbon dates of the samples analyzed after the excavations in and 7. The and excavations at Yuchanyan opened an area of 46 m 2 , with an excavation grid subdivided into squares Fig. We also excavated a one meter square in T4 and cleaned all of the sections to clarify the exposed stratigraphy.
In addition to the radiocarbon dating reported here, we studied site formation processes using micromorphology and mineralogy. A taxonomic and taphonomic study of the fauna was also carried out The small collection of lithic artifacts recovered was recently recorded and found to reflect the same tool categories, dominated by core-choppers and retouched flakes, known from the first excavations. A few bone and shell tools were reported previously The bedrock of Yuchanyan Cave slopes steeply from the east, where it is about 2.
The cave can be roughly subdivided into 3 main areas differentiated mainly by major rockfalls. The western area mainly square T1 is composed of 2 major lithostratigraphic units: Specifically, they are stringers composed of white and light gray calcitic ash lenses that in some cases overlie discontinuous bands of red clay, which are approximately 1—3 cm thick by approximately 30—50 cm long. The many ashes and red bands are compact and massive, with millimeter-size aggregates of red clay Figs.
Well-bedded lenses with varying white and red colored fine-grained sediments are separated by brown colored sediments. The major mineral components of these sediments are calcite, quartz, and clay. The central area squares T3 and T4 contains brown colored sediments with fewer lenses. The sediments here are also composed mainly of calcite, quartz, and clay. The eastern part of the cave square T5 contains massive brown sediments with almost no color differences, and stratification is not clearly visible.
These sediments are also dominated by calcite, quartz, and clay. Micromorphological analyses of the sediments clearly show that the calcite is mainly composed of wood ash that has been weakly cemented. The ash is remarkably well-preserved, and in many samples, rectangular pseudomorphs of wood-derived calcium oxalate crystals can be observed. Furthermore, much of the red clay Fig. S2 was purposefully brought into the cave, as there are no possible geological means for clay to accumulate as lenses within the cave.
In fact, the massive lenses e. S1 are constructed surfaces and are virtually identical to similar features from the Paleoindian site of Dust Cave in Alabama Note, too, that the clay component extracted from white lenses also often showed these characteristics. Thus, the exposure to elevated temperatures was probably part of the normal use of fires and was not associated with the production of ceramics. Photograph of the section in square T11 showing the calcitic ash lenses and reddish clay-rich lenses. One of the ceramic sherds was found embedded in this sequence. Its location is marked with O.
The distribution of bones was more or less uniform in all areas of the cave.
In contrast, the charcoal was much less abundant in the eastern T5 square, especially in the deeper part of the section. For both bone and charcoal, the proportions of dateable samples in squares T4 and T5 were much less than for the squares in the eastern parts of the cave. The preservation conditions are clearly much better in the western part of the cave.
What can be dated?
The results of the prescreening procedure are presented in Table 2. Prescreening results for bones and charcoal from different excavation squares in the cave. Seventy-five charcoal samples were selected, prescreened, and pretreated. As clay is a potential carbon carrier and therefore a possible contaminant, these samples were excluded.
Furthermore, an additional 8 samples dissolved completely during the procedure. Twenty of these samples that contained relatively large amounts of material were also analyzed by Raman spectroscopy The average fluorescence intensity after the first and last HCl steps decreased in all samples except for 4 YAS d, , , and T1E 6 , indicating that most of the humic acid was removed during the acid-alkali-acid AAA treatment.
These 4 samples were also rejected. Sixty-seven bones were analyzed from the different areas in the cave. All were treated with 1N HCl, and an acid insoluble fraction was identified in 43 samples. This fraction was then isolated, and 25 samples were shown to produce a pure collagen infrared spectrum. The weight percentage of insoluble collagen ranged from 0. The infrared splitting factor IRSF values of 4 samples were within 2.
In some of the collagen spectra, the presence of humic acid was detected; therefore, after whole pretreatment, the collagen was again characterized by infrared spectroscopy before target preparation for accelerator mass spectrometry AMS dating A total of 27 samples were analyzed for their 14 C contents. They were selected based on the quality of context and material preservation. Of these, 10 pretreated samples were separated into 2 parts and were prepared separately as duplicate analyses.
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Three samples BA , a, b 12 were analyzed during the s excavations when prescreening procedures were not used Table 1. Table 3 lists the 40 radiocarbon dates according to excavation square, and within each square the samples are arranged according to increasing stratigraphic depth. The duplicate analyses are also listed. The uncalibrated and calibrated ages are shown.
All of the radiocarbon dates were calibrated with OxCal 3. The samples are ordered by stratigraphic depth. The results from the western section T9, T1, TT12 are followed by those from the eastern section T5. Note that there is a distance of about 5 m between the two areas in the cave. The reproducibility of the duplicate measurement analyses Fig. This result shows that there is no bias between the measurements, and that there is no consistent difference between charcoal and bone samples from the same depth or level. Plot of the duplicate measurements showing the distribution of the data and the analytical reproducibility.
Radiocarbon Dating
The data are reported in Table 2. This shows that the upper part of each section contains sediments from around 14,—13, cal BP. Older sediments were found close to the base of the sections in squares T1 D and E, as well as in squares T10— Most of these sediments are from around 18,—16, cal BP. A major exception is a bone sample which was just above bedrock in T1 that gave an age of 21, cal BP. In square T9, near the western cave wall, the ages are similar and show no trend with depth. Age distribution of the samples analyzed from Yuchanyan Cave. The samples are ordered according to stratigraphic depth following Table 3.
In each stratigraphic section from which samples were analyzed, the ages increase with increasing stratigraphic depth, with 2 exceptions. The dates show that the cave was occupied from around 18, to 14, cal BP Table 3. There were some periods from which no dates were obtained. This may be due to the sample distribution or because during these periods very little sediment may have accumulated.
How Do Scientists Date Ancient Things?
The mineralogical and micromorphological analyses of the sediments both indicate that ash calcite was a major component of almost all samples, implying that they were produced mainly during periods of human occupations. Another unusual anthropogenic activity is evidenced by the clay-rich sediment formed into lenticular bands that must have been brought into the cave by humans and functioned as prepared surfaces Fig.
The clay may have been red colored initially or became red due to heating. Snail shells found in the cave sediments were analyzed and almost all were found to be composed entirely of aragonite. As aragonite is less stable than calcite, its presence indicates that the preservation conditions were generally good for ash and bones Calcite, however, buffers the ground water to above pH 8, and this is often not conducive to the preservation of charred materials.
In fact, the prescreening showed that the charcoal was generally poorly preserved, especially in the eastern part of the cave, which today, at least, is much wetter than the western part We also note that less than half the bones contained acid insoluble collagen. This, too, points to relatively poor preservation conditions for organic matter. Bearing this in mind, we assume that the consistent dates obtained can be attributed to the rigorous prescreening procedures.
We did not analyze the radiocarbon contents of any of the samples that were rejected during the prescreening. The distribution of the dates in the 70—80 cm of the upper part of the ash and red clay deposits reflect a more or less undisturbed accumulation as the series of radiocarbon dates demonstrate an increasingly older age with depth Fig.
This is less clear in the area where most of the potsherds were found in Square T1. During the excavation, a sherd was found in sublayer 3E at cm below datum and some 40—50 cm from where the original cluster of reconstructable potsherds were uncovered during the previous excavations. The location is shown in Fig. The deposits in T1 between the large boulder and the northern section slope toward the northern wall of the cave and, in addition, were somewhat disturbed.
We note that the 2 samples RTT and RTT that are clearly out of the overall stratigraphic order are from this location. The calibrated ages for sediments associated with the cluster of the pottery in T1 are from 16, to 13, cal BP with 2 SD RTB , , , , and Table 3. The sherd that was found in Square T11 is underlain and overlain by sediments that date between 18, and 17, cal BP with 2 SD RTB , , , , and Bearing in mind that all of the samples dated were from a 10 cm thick sediment sequence that was rather disturbed, we conclude that the lower limit for the age of the ceramics is around 15, cal BP.
The upper limit is based on the fragment found in square T11 that is more firmly dated to 18, cal BP. Dates as early as 17, to 16, cal BP have been conjectured for the earliest pottery in East Asia, such as at the Xianrendong and Diaotonghuan sites in Jiangxi Province, but these could not be confirmed due to ambiguities in the stratigraphic sequences of these sites 8 , Our work in dating Yuchanyan Cave differs from previously dated early pottery sites in China in that it is based on high-precision dating the entire sequence of the deposits, and by doing this with small sampling intervals of only a few centimeters in the areas close to where potsherds were excavated.
The results obtained allow us to securely date the pottery in Yuchanyan Cave to as early as 18, to 17, cal BP 1 SD. This supports the proposal made in the past that pottery making by foragers began in south China.
In the field, samples from well-defined contexts for example ash lenses were collected with the associated sediments. All charcoal pieces were collected separately, placed in aluminum foil, and dried before closing. For the bones, preliminary tests were conducted on-site by dissolving a small bone fragment in 1N HCl and then determining if a light insoluble fraction was preserved. The light insoluble fraction indicates, but does not prove, that insoluble collagen is preserved.
Museum Conservation Institute Dating of Artifacts
As only about half the bones did have an insoluble fraction, we collected many more samples for an extensive prescreening in the laboratory. All of the samples that were selected in the field based on context and size for radiocarbon dating were subjected to further prescreening procedures to determine the state of preservation and their suitability for dating based on the quality parameters defined in ref.
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Sixty-four bones from squares T1, T4, T5, T9, T11, T12, T14, and T15 were initially checked in the laboratory for mineral crystallinity based on their splitting factor The splitting factors ranged from 2.