Holocene humans at Pontnewydd and Cae Gronw caves.

Aldhouse-Green, Stephen ; Pettitt, Paul ; Stringer, Christopher 等

The first well-documented examination of Pontnewydd Cave, in the Elwy Valley of northeast Wales, was conducted in the early 1870s by McKenny Hughes & Thomas (1874). Stone tools, recovered along with Pleistocene fauna, were compared to finds at Le Moustier and St Acheul, and a human molar tooth was discovered, looking 'quite as ancient as the rest'. Modern excavations, beginning in 1978, soon led to the discovery of hominid finds (Green 1981; Green et al. 1981; Green 1984; Green et al. 1989). Excavation was also conducted at two other near-by cave sites, Cae Gronw and Cefn (Green 1986; Green & Walker 1991).

A total of 17 hominid finds, securely stratified in Middle Pleistocene deposits, is known from Pontnewydd. Four other human specimens were recovered from contexts of 19th-20th-century date. To these may be added additional finds from Cae Gronw (Green 1986: 39). Three of these have now been dated using the Oxford Radiocarbon Accelerator (TABLE 1). Two specimens, PN2 and PN8, were considered possibly to have derived from the same individual; if so, the determination for PN2 should apply equally to PN8. At Cae Gronw cave, with a less complex but nonetheless comparable stratigraphic sequence to Pontnewydd, the only evidence of human activity comprises scattered human bones in derived contexts. The condition and context of the bones both suggested a Holocene age; one sample, an adult radius, was dated to verify this. Human remains, likely to be of Holocene age, are likewise known from Cefn but remain undated (Dawkins 1874: 159-61).

The uncalibrated determinations are expressed in radiocarbon years b.p. (before present - AD 1950) using the half-life of 5568 years. Isotopic fractionation has been corrected for, using the measured [[Delta].sup.13]C values quoted (to [+ or -]0-5 - 1.0 per mil relative to PDB) (Hedges et al. 1989; 1992). The samples dated at Oxford were demineralized, gelatinized and ion-exchanged in order to isolate the amino-acids, freeze dried and combusted. The [[Delta].sup.13]C ratios for each of the samples are within the expected range for British human skeletal material, and the yields of collagen and dateable carbon were good. Accordingly, no problems in chemistry were observed, and the resulting ages can be regarded as reliable.

Stringer's detailed study (1984: 162) of the Pontnewydd mandible was cautious: the metrical data would not 'exclude [it] from the morphological and metrical range of anatomically modern humans' and the tooth present 'can be matched much more readily among recent examples'. Again, he noted that the vertebra 'can be closely matched in recent large adult specimens'. In spite of this caution, a number of factors supported a Pleistocene attribution. The relative dating programme (Molleson 1984) concluded that the mandible and vertebra were 'of some antiquity' on the evidence of Uranium-308 concentration which, it was thought, could 'probably be used to distinguish Pleistocene from Recent material'. The molar PNS, it appeared, might be taurodont (Stringer in Green et al. 1989: 34-6). Other taurodont molars of undoubted Pleistocene age are known from the site, and this feature can be compared with the high incidence of taurodontism - a condition of enlargement of the pulp cavity and coalescence of the roots of molar teeth - among Neanderthal permanent molars (but the characteristic is also present among modern populations). And pre-19th-century Holocene material appeared completely absent (but, in 1995, a later Mesolithic microlith was recovered from the same recent context that yielded the mandible).

The direct dating of two of the four unstratified Pontnewydd samples has no implications for the study of the securely stratified Middle Pleistocene hominids, for no hypotheses were constructed on the basis of these finds. The recognition of this material as Holocene has archaeological effect, in limiting the distribution of hominid finds to one restricted area of the cave's East Passage, with a single find from the New Entrance. Even the tooth found by McKenny Hughes (Hughes & Thomas 1874) must now be regarded as doubtful since condition alone is clearly not a criterion for differentation of Middle Pleistocene and Holocene hominid finds at this site. (Its whereabouts are unknown.) Pontnewydd is a reminder of the need to verify, wherever possible, unstratified hominid finds by direct dating.

For the Post Glacial context, the implications are larger. Caves were certainly used as repositories for prehistoric burials; for Wales, we may note a number of instances, verified by radiocarbon dating (TABLE 2). The results, based on only nine sites, clearly do not cover the full chronological span of cave-use for burial. Some well-known sites, possibly or certainly of Neolithic age, are excluded because radiocarbon dates are lacking: several ossuary sites of Little Hoyle 'type' such as Perthi Chwarae with 16 individuals (Dawkins 1874: 152-6; Evans 1929: 165-8) and Gop Cave with 14 burials (Dawkins 1901); also Rhos Ddigre, where two human skeletons 'in a sitting position' were [TABULAR DATA FOR TABLE 2 OMITTED] discovered in a cave which also produced Neolithic pottery and axes among other finds (Dawkins 1874: 152-6; Evans 1929: 165-8; Grimes 1951: 28-9). It would be desirable to test the antiquity of burials from these sites. None of the undoubted Roman cave-burials in Wales has been radiocarbon-dated (Branigan & Dearne 1992). Nonetheless, the samples listed here lack explicit archaeological associations or other indication of likely age; they can be regarded as 'random'. At present, the distribution of mean dates displays concentrations in the 8th and 5th millennia b.p.

Acknowledgement. We are indebted to Derek Roe for reading this paper in draft.

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