Hillman's contributions to understanding of ancient diet and food procurement were in five areas:
Archaeobotanical methodology In the early 1970s Hillman recognised that traditional crop-processing in the mostly unmechanised village of Asvan led to distinctive, consistent assemblages of crop seeds, chaff and weed seeds that could also be recognised in archaeobotanical samples. Contemporary analysis of archaeobotanical samples by
Robin Dennell and others had recognised this variation, with the implication that ancient seed assemblages could not be treated uncritically as representative of crop use, but had not identified the close association with crop processing stages. Further fieldwork by
Glynis Jones in Greece put Hillman's results onto a firmly quantified basis, and this mode of interpretation of plant remains - in terms of crop processing stages such as winnowing and sieving - is now a standard component of archaeobotany, particularly in the Old World. Catherine D'Andrea and Ann Butler in Ethiopia, and Leonor Peña-Chocarro and Lydia Zapata in Spain and Morocco. Other scholars acknowledge his influence, for example in work on wild foods in Turkey by Füsun Ertuğ, and on crop-processing in India by S.N. Reddy. Hillman stressed the importance of first-hand knowledge of the ecology of wild food plants: "...perhaps... for too many years, we in archaeology have imagined that we could somehow research events of considerable ecological complexity - such as those surrounding the inception of cultivation - without ever needing to come to grips with the ecological detail". They concluded that selective pressures meant that morphological domestication in the form of loss rachis fragility could occur within 200 generations, thus 200 years for this annual crop. Current interpretations of archaeological data by
Dorian Fuller and others point instead to a prolonged process of domestication; nonetheless the debate is framed by the evolutionary theory and field data set out by Hillman and Davies. Difficulty in identifying the fragmented plant remains characteristic of early sites led Hillman to build an excellent seed reference collection. His identification guides often circulated in handwritten and drawn form. They were most influential with regard to wheat identification, playing an important part in the development in the 1980s of reliable criteria for identification of wheat chaff, particularly separation of tetraploid and hexaploid free-threshing wheat rachises.
infra-red spectroscopy and other forms of chemical analysis. and morphological criteria.
Origins of agriculture in southwest Asia The plant remains from
Abu Hureyra, Syria, remain central to any research into the
beginnings of farming in southwest Asia. The eight metres of occupation debris spanning about 4000 years of human occupation spans the period during which cultivation of wild cereals and when their domestication is thought to have occurred. The broad picture of plant exploitation is clear: in the Epipalaeolithic (Natufian) levels (phase Abu Hureyra 1) seeds of about 200 wild plant species are present, with about 20 of these as staples, representing a diverse, foraged diet. In the PPNB village (phase Abu Hureyra 2), the plant remains are dominated by 7-8 domesticated plants, including barley and emmer wheat. Other aspects remain hotly debated, particularly with regard to explanation of the causes of this shift in subsistence. Views of the dating of the site and its plant remains are divergent.
Radiocarbon dating indicates a
Natufian level occupied for c. 1000 years between c. 13,100 to 12,000 calendar years before present (years BP), and a PPNB level dating from 10,000–9300 years BP. However, the final excavation report proposed continuous occupation on the basis of the distribution of radiocarbon dates, and also proposed the presence of domesticated rye grains in the Natufian period; both propositions are disputed. Hillman and colleagues countered with the difficulty of collecting dung from wild animals. The extent to which the wild flora of pre-agrarian sites represents food remains is likewise debated at other archaeological sites of this period. The nature and cause of changes in plant use in relation to climate are also debated. Hillman originally proposed that wild food plants such as wild einkorn were foraged, in other words, collected from the wild. However, following detailed ecological modelling, Hillman and Moore proposed instead that the wild cereals had been under cultivation, probably in response to desiccation caused by the
Younger Dryas climate event at about 12,900 to c. 11,700 years BP. Connolly and Colledge propose instead that the observed shift in plant consumption to less desirable foodstuffs at Abu Hureyra 1 simply reflects the greater scarcity of wild cereals under the effects of the cooler, drier
Younger Dryas climate. In wider context, wild cereal and legume cultivation is widely accepted as likely at PPNA sites (11,600-10,500 years BP), but is not generally accepted for Epipalaeolithic sites. Reinterpretation of the Abu Hureyra plant remains will continue, both as new archaeobotanical data and theory arises from new excavations, and will be accelerated in the event of further analysis of the Abu Hureyra assemblages. The final publication summarises the results by seed density; it is likely that full quantification and renewed identification efforts will lead to fresh views.
Hunter-gatherer diet Hillman had a strong interest in hunter-gatherer diet independent of agricultural origins. Aside from Abu Hureyra, he also studied plant remains from the Palaeolithic site of
Wadi Kubbaniya in Egypt, dating to c. 18000 calendar years BP and rich in tuber remains. Seeds previously identified as domesticated cereal grains were shown to be mis-identified or intrusive from later layers. With his student Sarah Mason he also studied plant remains from
Dolní Věstonice II in the Czech Republic, dating to about 26,000 radiocarbon years BP. The assemblage included seeds and tubers. Hillman often cited ethnographic studies of hunter-gatherers, often from North America, but also (using his fluent Turkish, Russian and German) from obscure European sources too. In last 20 years, post-retirement, reconstructing the potential foraging diet of pre-agrarian Britain became Hillman's main project, in part carried out with
Ray Mears, the bushcraft instructor. Incorporating copious experiments in processing to remove toxicity and improve taste, and extensive use of ethnographic and archaeobotanical data, the resulting plant profiles are currently being edited and released by colleagues at UCL.
Ancient agriculture Hillman worked on material from many agricultural sites, including Can Hasan III and the Asvan project in Turkey, the PPNB layers of Abu Hureyra in Syria,
Mycenae in Greece, and numerous sites in Wales. These were not the main focus of his later work, and most of these remain to be fully published, with the exception of the PPNB layers of
Abu Hureyra, studied by Dominique de Moulins, and the Asvan sites studied by Jennifer Bates and Mark Nesbitt. Important material such as the
rye finds from Can Hasan III was published in interim reports. Many of Hillman's other students worked on agrarian sites; for the Near East these included Mike Charles in Iraq, and Sue Colledge in Syria.
Food remains Two sets of archaeological food remains sparked Hillman's wider interest in ancient food. The stomach contents of
Lindow Man, who was excavated in 1984, date to the Iron Age about 2000 years ago. Analysis by Hillman's student Tim Holden found that his last meal was a coarse wheat and barley griddle bread. At Wadi Kubbaniya Hillman observed human coprolites containing seeds. == Impact ==