Dating the onset of cereal cultivation in Britain and Ireland: the evidence from charred cereal grains

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1 Dating the onset of cereal cultivation in Britain and Ireland: the evidence from charred cereal grains Alex Brown When does Neolithic life begin in Britain? The author gathered up the current evidence for radiocarbon-dated first use of cereals, distinguishing between dates from charcoal in contexts with cereals, and dates from the charred grains themselves. The charred grains begin to appear around 4000 cal BC and become prominent in settlements between 3800 and 3000 cal BC. This correlates well with the appearance of megalithic tombs ( cal BC) and argues for a relatively rapid adoption of the Neolithic package during an experimental phase of two centuries, cal BC. The early cereals reported in the pollen record (from 5000 BC) are attributed to wild species. Keywords: Neolithic origins, British Isles, agriculture, cereals, radiocarbon Introduction This paper reviews the evidence for the dating of the onset of cereal cultivation in Britain and Ireland, based upon radiocarbon-dated remains of charred cereals and also of dated contexts containing charred cereals. Many more sites with charred cereal grains are now available than existed at the time of an earlier survey by Moffett et al. (1989). Although cereal remains are far less common on Neolithic sites than, say, charred hazelnuts, in part due to differing taphonomic factors (Jones 2000), this survey demonstrates that cereals are far more widespread across the British Isles than earlier surveys suggest, irrespective of their dietary contribution (see Jones & Rowley-Conwy 2007, for a recent review of the importance of cereals in Neolithic Britain). In addition, many more of these sites have associated radiocarbon dates, an increasing number of which are high resolution AMS dates. This provides the opportunity to make meaningful comments on the chronological distribution of the evidence for cereal cultivation, and its implications for our understanding of the appearance, adoption and role of cultigens in the Neolithic of Britain and Ireland. Cereal cultivation is one of the defining characteristics associated with a Neolithic lifestyle, yet there is considerable debate over the precise dating of the first appearance of agriculture in the British Isles. Several authors (e.g. Pilcher & Smith 1979; Edwards & Hirons 1984; Williams 1989; Simmons & Innes 1996; Edwards & McIntosh 1998; Innes et al. 2003) have highlighted the growing evidence from the pollen record for cereal-type pollen grains Department of Archaeology, School of Human and Environmental Sciences, University of Reading, Whiteknights, PO Box 227, Reading RG6 6AB, UK ( a.d.brown@reading.ac.uk) Received: 23 November 2006; Accepted: 23 April 2007; Revised: 10 May 2007 antiquity 81 (2007):

2 Alex Brown in contexts dating to the late Mesolithic, some as early as c cal BC, often, though not exclusively, associated with evidence for vegetation disturbance. This has been taken to suggest the possibility of early pioneer agriculture up to several centuries prior to the generally accepted beginnings of the Neolithic in Britain and Ireland c cal BC. Precise dating of the onset of agriculture remains a key research aim for prehistoric studies, since the possibility of early agriculture has significant implications, both for our understanding of the transition to the Neolithic, and of human-plant relationships in the late Mesolithic. However, the evidence of cereal-type pollen grains, and their interpretation as proof of early, pre-neolithic cereal cultivation, remains contentious, not least because of the difficulties inherent in separating cereal-type pollen from that of wild grass pollen that make positive identification of cereal cultivation uncertain (see Tweddle et al for a recent review). Andersen (1979) separated Poaceae pollen into four groups (wild grasses, Hordeum group, Avena-Triticumgroup and Secalecereale). The Hordeum group (Barleys) includes only two cultivated species (Hordeum vulgare and Triticum monococcum), but several wild grass species, the Avena-Triticum group (Oats and Wheats) comprising only one wild grass species (Avena fatua), the remainder being those of cultigens. Cereal-type pollen of the Hordeum and Avena-Triticum groups are distinguished from wild grasses primarily on the basis of mean pollen grain and annulus diameters (cereal pollen grains being larger than those of wild grass species), but also the surface sculpturing of the pollen grain and the protrudance of the annulus. However, key distinguishing features are not always easy to identify where variable preservation of pollen grains occur, in which case caution should be exercised in any identification based upon grain and annulus diameter alone. Large cereal-type grains can also occur through swelling of wild grass pollen mounted in glycerol jelly, and as a result of genetic mutation (e.g. polyploidy), commonplace amongst the majority of plant species. In addition, several palaeoenvironmental studies have also produced cereal-type pollen grains from contexts significantly pre-dating the Neolithic (e.g. O Connell 1987; Tweddle et al. 2005), including late glacial contexts (O Connell et al. 1999) that most probably represent wild grasses or unusually large polyploid grains. It is the opinion of this author, given the inherent uncertainties regarding the cereal-type pollen record, that the only positive evidence for early cultivation is the presence of charred cereal grains from securely stratified and well-dated contexts. Method Results A total of 93 sites with charred cereal remains have been catalogued from across the British Isles. This by no means represents a complete inventory of sites with charred cereals, although every effort has been made to include those sites with accompanying radiocarbon dates. Additional records from archive reports are, however, listed in Jones and Rowley- Conwy (2007: Table 1). Cereal impressions on pottery, ard marks and saddle querns have been excluded from this survey. Although cereal impressions on pottery suggest cultivation, there is no means of accurately determining for how long a pot was in use prior to deposition. Additionally, only two sites with cereal grain impressions have accompanying radiocarbon dates, and at Windmill Hill are associated with charred cereal grains anyway (Whittle et al. 1999). The presence of ard marks below megalithic chambered tombs provide tantalising 1043

3 Dating the onset of cereal cultivation in Britain and Ireland evidence for possible cultivation prior to megalithic construction, but, other than South Street, Wiltshire (Evans 1971), do not have accompanying radiocarbon dates, do not include associated charred cereal remains, and may, alternatively, represent ritual preparation of the soil prior to monument construction. Saddle querns were excluded as they could equally have been used for the processing of wild plants. Of these 93 sites, 44 (48 per cent) are from England, 28 (30 per cent) are from Scotland, 16 (17 per cent) are from Ireland, and 5 (5 per cent) are from Wales. However, radiocarbon dates are available from only 58 of these sites, totalling 112 radiocarbon dates (Figure 1). Only 38 of these dates are derived from charred cereal grains, representing 11 of the 58 sites (19 per cent). Roughly half of English and Irish sites with charred cereal remains have associated radiocarbon determinations. This compares to 86 per cent of Scottish and 80 per cent of Welsh sites, though in the latter case this represents only four sites. Disparities exist, therefore, between England, Scotland, Ireland and Wales, not only in the number of sites from which charred cereals have been recovered, but in the radiocarbon coverage of these sites. The precision of these radiocarbon dates vary enormously, primarily as a function of differences in standard error between samples. Radiocarbon dates with large standard error will produce large calibrated date ranges and vice versa. Standard errors of accompany the radiocarbon dates from both Hembury and Townleyhall, and in such cases should be interpreted with extreme caution. Accuracy is further reduced where dates fall on plateaux on the calibration curve. For example, radiocarbon dates with similar standard errors will produce different calibrated date ranges dependant on their position on the calibration curve, with those dates falling on plateaux producing larger date ranges. The radiocarbon determinations presented here are, therefore, interpreted on the basis of the calibrated rather than uncalibrated dates, bearing in mind the above caveats regarding precision. Radiocarbon dates are calibrated using atmospheric data from Reimer et al. (2004) and OxCal v.3.10 (Bronk-Ramsey 2005), quoted at 95.4 per cent confidence. The dates are presented as a multiplot in Figure 1. The 112 calibrated radiocarbon dates presented in Figure 1 cover a time period from 4713 to 2190 cal BC. A key aim has been to differentiate between radiocarbon dates derived from charred cereals as opposed to dates derived from charcoal from contexts containing charred cereals. The significant problem when dating charcoal is the possibility that the sample is derived from old wood already centuries old at the time of deposition, or is intrusive within a later feature. This is evident from Billown, Isle of Man, where charcoal from two pits (F526 and F68) containing charred cereals, cut into the earliest ditch of a causewayed enclosure, produced early dates of BP (Beta , cal BC) and BP (Beta , cal BC, Darvill 1999). A subsequent programme of radiocarbon dating on charred cereals produced consistently later dates than those derived from charcoal. Charred cereals from F526 produced a date of BP (OxA-10140, cal BC, Darvill 2000), years older than the previous charcoal date. The difference in dates is too great alone to suggest old wood, as north-west-european deciduous trees such as oak typically do not live for more than c. 500 years. This suggests that the earlier date is most-probably derived from intrusive charcoal deposited within a much later feature. The majority of radiocarbon dates fall within the fourth millennium cal BC (Figure 1), with a marked concentration of calibrated date-ranges distributed between 1044

4 Alex Brown Method Figure 1. OxCal plot of radiocarbon dated cereals and contexts containing cereals. Symbols relate to the following dated material: * charcoal, # human/animal bone, > charred flax, + charred cereal grain, ˆ hazelnut shell, organic residue,? not published. References for individual sites provided online in Table 1 (see (Atmospheric data from Reimer et al. (2004); OxCal v3.10 Bronk Ramsey (2005); cub r.5 sd:12 prob usp[chron]). 1045

5 Dating the onset of cereal cultivation in Britain and Ireland Figure 1. (cont.) 1046

6 Alex Brown Method Figure 1. (cont.) 1047

7 Dating the onset of cereal cultivation in Britain and Ireland cal BC. Only a very small number of sites with cereal remains produced dates within the third millennium cal BC. The earliest radiocarbon dates, all derived from charcoal, are from the Hembury causewayed enclosure, dated to BP (BM-138, cal BC) and BP (BM-130, cal BC: Moffett et al. 1989). This is comparable to an early date of BP ( cal BC) from Cowrie road, Bannockburn (Rideout 1997). However, the large standard errors of the Hembury dates (+ 150) and large calibrated date ranges ( years) render these dates highly unreliable indicators of the earliest cereal cultivation. Radiocarbon dates on charcoal from Gwernvale, Bog Head, Ballygalley and Lismore Fields produced date-ranges covering c. 350 years, extending back from as early as c cal BC, whilst a slightly later radiocarbon date of BP (AA-20409) from Cowrie road produced a date-range between cal BC (Rideout 1997). Charcoal from contexts containing cereals at Ballyharry site 1 produced a date of BP (UB-4202, cal BC, McSparron 2003), a date-range at a 95 per cent confidence of only 90 years. However, the possibility that these early dates are derived from old wood should not be excluded. The earliest dates on charred cereals from Lismore Fields and Billown, of BP (OxA-2434) and BP (OxA-10140) produced dateranges between 3930/ cal BC. Radiocarbon dates derived from charcoal would suggest cereal cultivation first occurring perhaps as early as 4050 cal BC, but no later than 3770 cal BC. However, dates on charred cereals suggest cultivation first occurring no earlier than 3950 cal BC, but no later than 3630 cal BC. Discussion Contrary to the evidence for early pioneer cultivation at c cal BC suggested by the cereal-type pollen record, the evidence from charred cereals suggests cultivation first occurring no earlier than c cal BC and certainly no later than 3630 cal BC. The combined date range for first cultivation derived from charred cereals and dated contexts containing cereals of c. 400 years is unacceptably large at present. This date range can only be tightened further by repeat AMS dating charred cereals from those sites with earlier dates currently derived from charcoal (e.g. Ballygally, Ballyharry and Cowrie Road), and on which some caution must be exercised because of the possibility of earlier dates derived from old wood. The earliest dates for first cultivation from charred cereals are 100 years later in date (c cal BC) than the earliest dates derived from charcoal (c cal BC). The interpretation advanced here, on the basis of the present radiocarbon data, suggests limited cultivation of cereals at c cal BC, with the majority of the dates distributed between cal BC, followed by a significant reduction in the evidence for crop cultivation during the later Neolithic. The radiocarbon dates from this study accord well with the accumulated radiocarbon dating evidence for the origins of megalithic tombs in both Ireland (Sheridan 2003), England, Scotland and Wales (Schulting & Whittle 2003) that show a small number of dates around c cal BC, with the majority of dates falling between cal BC. The dating evidence from Cotswold-Severn tombs, recently synthesised by Darvill (2004), suggest tomb construction largely beginning around c cal BC, with dates on human 1048

8 Alex Brown bones generally falling between cal BC. Recent AMS dates on human bone from Burn Ground, Gloucestershire have produced a series of calibrated date-ranges between cal BC, with an early date of cal BC that may represent longterm curation of ancestral remains, rather than a Mesolithic origin for tomb construction (Smith & Brinkley 2006). Radiocarbon dates on houses from Ireland (Grogan 2002), Scotland (Barclay 1996; 2003), England and Wales (Darvill 1996; Mercer 2003) also show a number of early dates between cal BC and 3900/3800 cal BC (see online Table 1 at However, McSparron (2003) has recently suggested that early (c cal BC) dates from Irish Neolithic houses may be displaying an old wood effect, with non old-wood samples consistently producing determinations on houses within a date-range of cal BC. Pottery traditions also seem to become established over most of Britain and Ireland between cal BC (Herne 1988). Furthermore, dendrochronological dates on the Sweet Track, the earliest wooden structure in the British Isles, place its construction at 3806/7 cal BC (Coles & Coles 1986). Causewayed enclosures appear to be a slightly later feature of the early Neolithic landscapes, with some dates for construction occurring around c cal BC (e.g. Barclay 2001; Sheridan 2001), but with a concentration between cal BC (Oswald et al. 2001). These dates seems to suggest an apparent uniform appearance of various elements associated with a Neolithic lifestyle from c cal BC, but that only seem to become an established feature of the Neolithic landscape from c cal BC. Moreover, Schulting and Whittle (2003) highlight that there is little spatio-temporal patterning in the radiocarbon dates from chambered tombs across the British Isles, and this is reflected in the dates associated with charred cereals and houses, suggesting, as Schulting and Whittle (2003) argue for, a rapid,andtherefore,potentially...interconnectedphenomenon across Britain and Ireland. However, this apparent interconnected phenomenon may hide a more complex pattern of Neolithic origins during the initial centuries of the fourth millennium cal BC ( cal BC), one that may only become more obvious through continued and repeated AMS dating of early Neolithic contexts. This might see an early origin for cultivation, domestic structures and mortuary traditions within particular pockets of the Neolithic landscape around c cal BC, perhaps reflecting changing individual community life-ways that did not become a more established feature of the Neolithic landscape until c cal BC. Richards et al. (2003) recently argued for a sharp shift in dietary intake from marine to terrestrial resources over the Mesolithic-Neolithic transition rather than the long drawn out transition favoured by others (e.g. Thomas 1999). The radiocarbon dating evidence from charred cereals, burial monuments and domestic structures could be taken to suggest a period of perhaps as little as years at the beginning of the fourth millennium cal BC ( cal BC) where traditional hunter-gatherer life-ways persisted amongst communities experimenting with elements of a Neolithic lifestyle before becoming more widely established. Evidence for the continued accumulation of shell middens along the British and Irish coastlines into the early Neolithic, and the widespread evidence for the continued exploitation of wild plant resources throughout the Neolithic (e.g. Moffett et al. 1989; Jones 2000; Robinson 2000) demonstrate that some elements of a hunter-gathering lifestyle did not disappear completely. Method 1049

9 Dating the onset of cereal cultivation in Britain and Ireland Schulting and Richards (2002) have argued that there is very little in the way of supporting evidence for models hypothesising a gradual transition. The hypothesis advanced here is that this transition may have occurred within the years from 4000/ cal BC. It is not presently possible to refine this chronology because of a plateau in the calibration curve from cal BC that means even AMS dates at this crucial point, could, conceivably, fall anywhere within this 200-year period. This does not explain away the concentration of dates from cal BC, but it does highlight that radiocarbon dating alone is not the key to refining our understanding of this crucial 200-year period at the beginning of the Neolithic. A further aspect of the calibrated date ranges for cultivation presented here, is the distribution of the majority of dates between cal BC, and the comparatively few dates following 3000 cal BC. This accords well with the pollen evidence from Ireland for cereal cultivation, recently synthesised by O Connell and Molley (2001), that is argued to show a concentration of farming in the earlier Neolithic c cal BC, with minimal levels of farming thereafter. However, debate has tended to centre on the relative contribution of cereals to Neolithic subsistence strategies (e.g. Jones 2000), that, irrespective of whether one sees them playing a significant dietary role or not, does little to explain the concentration of evidence for cultivation during the fourth millennium cal BC. Dark and Gent (2001) have recently argued that the probable relative resistance to pests and diseases of the principal prehistoric crops, grown at low-intensity within a predominantly wooded landscape, combined with optimal climatic and soil conditions, may have resulted in a honeymoon period for crop cultivation in north-western Europe during the early Neolithic characterised by initially high crop yields. While the probable initial resistance of crops to pests and diseases may have been attractive to early Neolithic people, the close relationship between the dates from charred cereals, chambered tombs and houses, suggest that other factors, both social, cultural and economic, as well as environmental, interacted variously in determined the adoption of cultivation and subsequent patterns of land-use across the British Isles. Conclusion Radiocarbon dates on charred cereals suggest that the onset of crop cultivation in Britain and Ireland occurred no earlier than c cal BC. However, radiocarbon dates derived from charcoal from contexts containing charred cereals suggest cultivation occurring perhaps as early as c cal BC. The possibility that these dates may derive from samples of old wood requires testing by AMS dating of the charred cereals from these sites. The onset of cereal cultivation indicated by charred cereal grains is in broad agreement with the earliest dates from megalithic chambered tombs and domestic structures from Britain and Ireland. Only a small number of dates fall between 4000/3950 and 3800 cal BC, the majority occurring from cal BC, with less evidence for cultivation thereafter. The present dating evidence suggests a transitional period of perhaps some years between 4000/3950 and 3800 cal BC before a Neolithic lifestyle became a more established feature of the British and Irish landscapes. This lends support to recent theories hypothesising a rapid rather than gradual transition from Mesolithic to Neolithic lifeways. 1050

10 Alex Brown The consistency of the dating evidence from cereals, tombs and domestic structures, argues against dates for crop cultivation as early as c cal BC suggested by the cerealtype pollen evidence. It is considered more probable that these pollen grains are derived from wild grasses rather than cultigens. Acknowledgments This paper developed from aspects of the author s doctoral research, funded by a University of Reading postgraduate scholarship held in the Department of Archaeology, supervised by Professor Martin Bell and Dr Petra Dark. I am grateful to Richard Bradley for comments on earlier drafts of this paper, and to Cormac McSparron for access to recently published data on the Neolithic houses at Enagh, Co Derry. I am also grateful to the referees for their comments, and, in particular, Peter Rowley-Conwy for access to material in press at the time of writing. References Andersen, S. Th Identification of wild grass and cereal pollen. Danmarks Geologiske Undersøgelse. Årborg. 1978: Barclay, G.J Neolithic buildings in Scotland, in T. Darvill & J. Thomas (ed.) Neolithic houses of northwest Europe and beyond (Neolithic Studies Group Seminar Papers 1): Oxford: Oxbow Neolithic enclosures in Scotland, in T. Darvill &J.Thomas(ed.)Neolithic enclosures in Atlantic northwest Europe (Neolithic Studies Group Seminar Papers 6): Oxford: Oxbow Neolithic settlement in the lowlands of Scotland: a preliminary survey, in I. Armit, E. Murphy,E.Nelis&D.Simpson(ed.)Neolithic settlement in Ireland and western Britain: Oxford: Oxbow. Bronk-Ramsey, C OxCal version 3.10 radiocarbon calibration programme.oxford. Coles, B. & J. Coles Sweet track to Glastonbury. London: Thames & Hudson. Dark, P. & H. Gent Pests and diseases of prehistoric crops: a yield honeymoon for early grain crops in Europe. Oxford Journal of Archaeology 20: Darvill, T Neolithic buildings in England, Wales and the Isle of Man, in T. Darvill & J. Thomas (ed.) Neolithic houses in Northwest Europe and Beyond (Neolithic Studies Seminar Papers 1): Oxford: Oxbow Billown Neolithic landscape project, fourth report: 1998 (Bournemouth University School of Conservation Sciences Research Report 5). Bournemouth Billown Neolithic landscape project, fifth report: 1999 (Bournemouth University: School of Conservation Sciences Research Report 6). Bournemouth Long barrows of the Cotswolds and surrounding areas.stroud:tempus. Edwards, K.J. & K.R. Hirons Cereal pollen grains in pre-elm decline deposits: implications for the earliest agriculture in Britain and Ireland. Journal of Archaeological Science 11: Edwards, K.J. & C.J. McIntosh Improving the detection rate of cereal-type pollen from Ulmus decline and earlier deposits from Scotland. Pollen et Spores 30: Evans, J.G Habitat change on the calcareous soils of Britain: the impact of Neolithic man, in D.D.A. Simpson (ed.) Settlement and economy in the Neolithic and early Bronze Age Britain and Europe: Leicester: Leicester University Press. Grogan, E Neolithic houses in Ireland: a broader perspective. Antiquity 76: Herne, A A time and place for the Grimston Bowl, in J. Barrett & I.A. Kinnes (ed.) The archaeology of context in the Neolithic and Bronze Age: recent trends: Sheffield: Department of Archaeology and Prehistory, University of Sheffield. Innes, J.B., J.J. Blackford & P.J. Davey Dating the introduction of cereal cultivation to the British Isles: early palaeoecological evidence from the Isles of Man. Journal of Quaternary Science 18: Jones, G Evaluating the importance of cultivation and collection in Neolithic Britain, in A.S. Fairbairn (ed.) Plants in Neolithic Britain and beyond (Neolithic Studies Group Seminar Papers 5): Oxford: Oxbow. Jones, G. & P. Rowley-Conwy On the importance of cereal cultivation in the British Neolithic, in S. Colledge & J. Conolly (ed.) Origins and spread of agriculture in SW Asia and Europe: archaeobotanical investigations of Neolithic plant economies: , Walnut Creek (CA). Left Coast Press. McSparron, C The excavation of a Neolithic house and other structures at Enagh, County Derry. Ulster Journal of Archaeology 62: Method 1051

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