Abstract Use-wear analysis of five glossed flint blades found at Ohalo II, a 23,000-years-old fisher-hunter-gatherers’ camp on the shore of the Sea of Galilee, Northern Israel, provides the earliest evidence for the use of composite cereal harvesting tools. The wear traces indicate that tools were used for harvesting near-ripe semi-green wild cereals, shortly before grains are ripe and disperse naturally. The studied tools were not used intensively, and they reflect two harvesting modes: flint knives held by hand and inserts hafted in a handle. The finds shed new light on cereal harvesting techniques some 8,000 years before the Natufian and 12,000 years before the establishment of sedentary farming communities in the Near East. Furthermore, the new finds accord well with evidence for the earliest ever cereal cultivation at the site and the use of stone-made grinding implements.

Citation: Groman-Yaroslavski I, Weiss E, Nadel D (2016) Composite Sickles and Cereal Harvesting Methods at 23,000-Years-Old Ohalo II, Israel. PLoS ONE 11(11): e0167151. https://doi.org/10.1371/journal.pone.0167151 Editor: John P. Hart, New York State Museum, UNITED STATES Received: August 23, 2016; Accepted: November 9, 2016; Published: November 23, 2016 Copyright: © 2016 Groman-Yaroslavski et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All relevant data are within the paper. Funding: This work was funded by Israel Science Foundation (Nos. 831/00 and 711/08), Jerusalem Center for Anthropological Studies, L.S.B. Leakey Foundation, Stekelis Museum of Prehistory in Haifa, MAFCAF Foundation, National Geographic Society, and Israel Antiquities Authority. Competing interests: The authors have declared that no competing interests exist.

Introduction The use of plant resources as food is evident from the earliest days of humankind [1]. Likely, these foods were gathered by bare hands or by using simple ad-hoc tools. By the end of the Pleistocene, the Natufians (ca. 15,500–11,600 Cal BP) of the Near East commonly used a composite harvesting tool, the sickle. These sickles were composed of a handle made of bone or wood, and flint blade(s) or bladelet(s) inserted in it, as found at Natufian sites such as el-Wad in Mount Carmel, northern Israel [2] and Wadi Hammeh 27 in Jordan [3]. The hafted Natufian blades/bladelets have typical sickle sheen (later identified through use-wear analysis, see below). Such glossed elements, commonly termed sickle blades in local literature, were found in small numbers in many Natufian sites, and in larger numbers in the proceeding Neolithic sites [4]. Pre-Natufian sickle handles have not been found yet, and reports of isolated blades with faint sickle sheen are also rare. We report here the presence of five blades with apparent sheen at Ohalo II, a 23,000-years-old fisher-hunter-gatherers' camp on the shore of the Sea of Galilee. Furthermore, use-wear evidence for cereal harvesting is combined with hafting indications on some of the blades. This is the earliest evidence for such a composite harvesting implement, a tool that became a hallmark of Early Neolithic tool kits some 12,000 years later. The aims of this paper are to describe the five Ohalo II glossed blades and the results of their use-wear analysis, to shortly present our experimental harvesting project, and to discuss the implications for reconstructing cereal economy at Ohalo II. The earliest evidence of sickles In the Levant, the earliest appearance of glossed blades in the archaeological record is during the Early Epipaleolithic period. Although rare, isolated flint blades with weak sheen were mentioned from Kebaran sites (ca. 23,000–18,000 cal BP) such as Ein Gev I to the east of the Sea of Galilee: "A few blades with luster (undoubtedly close but not identical to the Natufian sickle blades) were also found" [5]. However, only in the Natufian do such elements become relatively common. In these sites, the sheen is found on both blades and bladelets, and their frequencies in the tool kits are usually in the range of <1%–5% (e.g., the Late Natufian sites of Eynan layer1b: 0.3% in northern Israel [6]; el-Wad 1.8% in Mount Carmel, northern Israel [7]; Fazael IV 4.8% in the southern Jordan Valley [8]). The Natufian glossed implements, and for that matter the Neolithic ones too, were commonly perceived as associated with cereal harvesting. Indeed, already in 1892 Spurrel studied glossed items under the microscope and concluded that the glossy appearance was produced by friction with cereal stems [9]. Since then glossed blades and bladelets are commonly catalogued as sickle blades in the typo-technological analyses of flint assemblages in the Levant, and often interpreted as an indication of one of the most important developments in human subsistence technology, namely, the cultivation and later the domestication of cereals [10,11]. In the case of cereal harvesting tools, the investigation of Levantine Natufian and Neolithic sickle blades by the application of the methodological framework of use-wear analysis during the 80's and 90's provided a platform for reconstructing incipient agriculture, including aspects related to field conditions, species of crops and harvesting methods [12–17]. The study of cereal gloss was also a platform to investigate wear formation processes [18–22], and recently cereal gloss on flints was analyzed by the application of laser confocal microscopy [23,24]. Yet, it is reasonable to assume that cereal grains were consumed by humans much earlier than the fluorescence of the Natufian culture. In the Levant, the earliest examples include cereal grains found in Middle Paleolithic Kebara Cave in Mount Carmel, northern Israel [25] and Amud Cave in the Lower Galilee, northern Israel [26]. Evidence of cereal starch entrapped in European Upper Palaeolithic grinding tools demonstrates their use for plant food processing [27–29]. The site of Ohalo II Ohalo II is located on the southwestern shore of the Sea of Galilee in Israel (Fig 1). PPT PowerPoint slide

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larger image TIFF original image Download: Fig 1. a) Location map of Ohalo II. b) An aerial view of the site; the three loci where the glossed blades were found are marked. https://doi.org/10.1371/journal.pone.0167151.g001 It was submerged shortly after it was abandoned and remained as such for millennia [30,31]. The site was dated by over 50 14C dates of in situ remains, as well as of materials from pre-occupation and post-occupation layers [32–35]. Eleven loci were directly dated by 34 14C readings, mostly ranging between 22,500–23,500 cal. B.P. [30,32,33,36]. Two of the loci with the items discussed here were directly dated: Locus 3 with 12 radiocarbon dates and Locus 13 with 3 radiocarbon dates. The camp includes the remains of six brush huts and several clusters of hearths around them. In Brush Hut 1 the charred building materials of the walls were identified to the species level: thick branches of Tamarix sp. (Tamarisk), Salix sp. (Willow) and Quercus ithaburensis (Oak) were covered by smaller branches of plants such as Atriplex/Seidlitzia (Orach/Seidlitzia) and Prosopis sp. (Mesquite), as well as leaves and grasses [37]. Grass bedding encompassing charred bundles of Puccinellia cf. convoluta (Alkali-grass, a perennial grass) stems and leaves covered with a thin layer of compact clay was found on the bottom floor of Brush Hut 1 [36]. A grave of a male buried in a semi flexed position and a nearby stone circle were found near the brush huts [30]. A large faunal assemblage was found in all brush huts and fire places, including mammals, micro mammals, fish and birds [31,38,39]. A sample of ca. 160,000 charred and un-charred seeds and fruit remains comprising approximately 150 identified taxa was studied [40–44]. The presence of cereals in the plant assemblage is noteworthy. For example, on Floor II of Brush Hut 1 there were ca. 60,000 seeds and fruits, of which 606 are of Hordeum spontaneum (Wild barley) [45]. On Floor III there were ca. 55,000 specimens, of which 1,920 are from the same species [42]. Furthermore, evidence for grinding cereals on the floor of Brush Hut 1 was well-preserved. First, the unique distribution of cereal grains around a carefully set flat stone suggests the stone was used for food preparation [45]. Second, a thorough study of the stone, including sonication for the retrieval of microscopic remains, showed that the stone was indeed used for grinding wheat, barley and oats. The grinded cereals were supposedly used for making a baked product in an adjacent baking installation, which in turn increased the caloric intake of the inhabitants [46,47]. A use-wear analysis of the stone corroborates the previous conclusions [48]. Additional lower and upper grinding stones were studied, again reflecting the use of such implements in food processing at the site [48–50]. Furthermore, a recent botanical-ecological study showed that the Ohalo II people were cultivating cereals, probably on a small scale; this is by far the earliest example of its kind [51]. Thus, there is evidence at the site for cereal cultivation on the one hand, and for grinding and accordingly, consumption, on the other. Direct evidence for the relevant harvesting technology was missing. It is this gap that the current paper bridges by studying glossed flint implements, one of which was already briefly published [51].

Discussion The glossed blades from Ohalo II are the earliest evidence for the use of flint inserts as part of composite cereal harvesting tools, appearing more regularly only in Natufian sites, some 8,000 years later. Our use-wear analysis results provide new insights pertaining to past technologies and subsistence patterns. Within the Ohalo II flint assemblage, the five glossed specimens are outstanding in their morphometric characteristics, as they are much larger than the average blades at the site. They were not a regular product of the local reduction sequence, mostly aimed at the manufacturing of bladelets and small blades, indicating the selection of large rare flint artifacts for harvesting. The use-wear analysis shows that the Ohalo II glossed blades were used for cutting cereal stems at a near ripe semi-green condition. This was determined by comparison to our experimental tools where polish of identical characteristics was observed. Cereal grains found at Ohalo II are of wild species [40,42,45,51] and harvesting them semi-ripe indicates that the Ohalo II people already knew that harvesting the ripe cereals with a tool would result in shattering off the grains and in heavy loss of potential food [56,57]. Using a sickle also enhances the harvest event in terms of speed and precision. One of the outcomes of such a method was larger quantities of cereal stems of regular length, available for use at the site. Evidence for cereal processing at the site is clearest in Brush Hut 1, where a grinding slab was firmly set on the floor; microscopic wild cereal starch grains were extracted from its surface, and a patterned distribution of cereal seeds was found around it [45–47]. The use of composite sickles at Ohalo II, inferred by the presence of typical cutting and hafting wear (Figs 5 and 6), is the earliest ever documented. It implies preplanned harvesting endeavors, as specific tools and materials were prepared in advance, including the handle, flint inserts and adhesives. Evidence for the preparation of composite hunting tools, i.e. projectiles with several barbs, is also present at the site [58]. The distribution of the traces on the glossed implements indicates that blades were placed relatively protruding and parallel to the axis of the haft. It is intriguing that no adhesive residues were found on the blades because the site is well preserved, and some such residues were found even on small retouched bladelets [58]. One possible explanation is that there was no use of mastic and the blades were inserted by pressure into the socket of the haft. We could not reconstruct the material from which the hafts were made, although wood implements have been preserved at the site [59]. Sickle hafts found in Natufian sites such as Kebara cave [60], el-Wad cave [2,61], Hayonim cave [62], Wadi Hammeh 27 [3,63] and Zawi Chemi Shanidar in northern Iraq [64] were all made of long bones and horns [65]. Cereal harvesting by hand-held blades has also been identified in our analysis (Figs 4, 7 and 8). By comparing the distribution of the prehension wear it is evident that tools were held according to their morphology, exploiting a preferred edge to be used as an active edge. Compared to composite sickles, these tools may represent a more opportunistic nature of cereal harvesting. Still, they are unique in morphology and dimensions compared to most of the blades at the site, indicating selection of appropriate items for harvesting. The distribution pattern of the cereal use-wear polish (linked, smooth polish band, not wider than 1 mm right on the edge or very close to it, fading gradually in a reticular pattern) and its low intensity indicate short events of use. These differ substantially from Neolithic sickle blades in terms of sheen intensity and distribution on the specimen, commonly interpreted as reflecting multiple events of systematic harvesting [21]. Likely, the rarity of comet-shaped pits on the Ohalo II specimens also reflects low level of use. One blade interpreted to have been hafted (artifact AJ39c, Fig 6) was used more extensively than the others, but compared to our experimental tools it seems that each of the Ohalo II blades was used for no more than one or two harvesting days (or about 4 to 10 hours). One blade, showing two polished edges (artifact AL73c, Fig 5), likely represents an example of two events of utilization. However, both edges of this tool are still sharp and amenable for further work, therefore we cannot explain the reason of changing the working edge. Large quantities of wild cereal grains were found at the site, including barley, wheat and oats [41–43,45,51,66], yet cereal harvesting and cutting tools are rare. The vast majority of the Ohalo II grains are smooth (i.e. harvested when ripe), and do not exhibit signs of puckering, which is characteristic of younger, unripe grains [67]. It is thus reasonable to suggest that a variety of collecting methods such as uprooting, hand stripping, beating into baskets or collecting from the ground [14,57,68–72] have been commonly used at Ohalo II. The site was occupied year-round, as indicated by the remains of migratory birds and the timing of ripening of the identified plant remains [39,40,46]. The wide variety of plant species consumed and used at the site indicates the range of habitats exploited by the people and the wide dietary breadth exercised [40,44,47,73,74]. It would thus be reasonable to suggest that harvesting plant food in general, and cereal collecting in particular, incorporated several methods and tool types, according to season, distance from the site (e.g., carrying distance of tools and collected food), species, ripeness stage, and topographic location on the adjacent hill slopes. Addressing the rarity of sickle inserts, this is also the case in some Natufian sites, where sickle blades are hardly present or missing altogether. In such cases, as well as for Ohalo II, several explanations can be forwarded: Cereal harvesting using flint tools was a short duration task, therefore it is possible that polish hardly developed, and thus not visible to the naked eye. If this is indeed the case, it is possible that a systematic use-wear analysis of blades would reveal more tools. Tools used in the field could have been discarded at the end of a day's work. This is especially plausible in the case of tools held by hand and in opportunistic harvesting. In the case of using composite sickles, the flint inserts could be lost in the field during the harvest, especially if no mastic was used to fix them. In two of our harvesting experiments we lost inserts although they were fixed with mastic made of resin, bees wax and lime powder, yet this mastic is not strong as bitumen. Cereal stems may have been cut with flint tools only in rare cases; other techniques such as uprooting, basket collection and beating may have been the common way of harvesting. Use-wear analysis of Natufian sickle blades has been applied to specimens from several sites in the Levant, including Abu Hureyra and Mureybet in Syria, Ain Mallaha, Hayonim Terrace, Hilazon Tachtit, Nahal Oren, El-Wad, Kebara, Hatoula, Jericho, Saflulim, in Israel and Iraq ed-Dubb in Jordan [14–16,20,75–82]. Looking at the published micrographs and the associated reconstructions, it seems that the studied implements have similar characteristics to those observed for the Ohalo II glossed blades, namely, the linked polish at the actual edge, fading gradually in a reticular pattern. These sickles were also interpreted to indicate short duration harvesting events. However, some of the Natufian sickle blades show highly developed polish, not observed on the Ohalo II implements. The higher numbers of sickle blades in some Natufian sites, combined with a more frequent evidence of developed cereal use-wear polish, can be used as indications of the intensification of cereal harvesting using composite tools. The larger numbers of Natufian grinding and pounding implements [83,84] accords well with this increase of cutting tools. The distinction between semi-ripe and ripe cereal use-wear polish is an important aspect in the documentation of the evolutionary process of cereal cultivation leading later to domestication, as before domestication the harvest was most likely carried out at a semi-ripe stage, and for domesticated species it was at the ripe stage. The change in shattering characteristics and thus reaping stage and method of harvesting reflects a long process led by human selection [85,86]. The Ohalo II inhabitants were among the first to identify the ear-shattering problem and to find a technological solution. Unfortunately, due to poor preservation of organic remains in contemporaneous sites and even in most Natufian sites, we have no idea if the Ohalo II case was a short-lived isolated event that was re-invented thousands of years later, or if it was the beginning of a long continuous evolutionary process of which many of its stages are missing [87,88]. At any rate, the Ohalo II inhabitants also used grinding technology [46,48,50], albeit on a small scale, as is the case in isolated Upper Paleolithic sites in Europe [28,29]. According to the Levantine archaeological record, both harvesting and grinding technologies appeared more-or-less at the same time, and became wide-spread and commonly used only eight millennia later. The scarce archaeological remains of both technologies thus suggest a limited reliance of pre-Natufian societies on cereals. The Natufians, with their large sedentary or semi-sedentary settlements and their new subsistence patterns, were the first to incorporate and develop these two technologies to enable cereal consumption on a new wide level; shortly after it became the hallmark of the Near Eastern Neolithic village. The excellent and rare preservation at Ohalo II provides a unique combination of finds that include cultivated cereal grains of two species, an in situ grinding slab with cereal grains around it, microscopic cereal starch remains and grinding use-wear evidence on its upper side, as well as the use-wear evidence on flint blades used for cereal harvesting in a semi-ripe stage. It is this range of finds that indicates that the Ohalo II people were innovative, and even without knowing so were the first on a long, likely intermittent, bumpy road finally leading to the establishment of agriculture.

Acknowledgments The Ohalo II project was generously supported by the Irene-Levi Sala CARE Archaeological Foundation, The Israel Science Foundation (Nos. 831/00 and 711/08), the Jerusalem Center for Anthropological Studies, the L.S.B. Leakey Foundation, the Stekelis Museum of Prehistory in Haifa, the MAFCAF Foundation, the National Geographic Society and the Israel Antiquities Authority. We thank the Israel Nature and Parks Authority for the permission to conduct some of the experiments in the fields of Mount Carmel. Digital figures were prepared by Anat Regev-Gisis.

Author Contributions Conceptualization: IGY EW DN. Data curation: IGY. Formal analysis: IGY. Funding acquisition: DN. Investigation: IGY. Methodology: IGY. Project administration: IGY DN. Resources: IGY DN. Software: IGY. Supervision: IGY DN. Validation: IGY. Visualization: IGY DN. Writing – original draft: IGY EW DN. Writing – review & editing: IGY EW DN.