Poggetti Vecchi, Tuscany, Italy; evidence of the use of fire for working wooden implements by Neanderthals (∼171,000 years B.P.)

Wooden artifacts were found in the stratified site of Poggetti Vecchi in southern Tuscany (central Italy) that was dated to the final Middle Pleistocene.

A multidisciplinary research has been conducted on the paleoenvironmental conditions at the time of the formation of the site. Due to the low resistance to decay of wood, prehistoric wooden tools, and especially early Middle Paleolithic ones, are very rarely found. Wooden spears are known from a few European localities.

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Poggetti Vecchi is located near Grosseto (southern Tuscany) in a confined, depressed plain at the foot of an 11-m-high hill. Warm water springs occur locally, connected with the intense geothermal system present in many areas of southern Tuscany. In 2012, diggings for a thermal pool exposed an about 3-m-thick succession of lithostratigraphic units. A following systematic excavation over an area some 60 m2 wide, supervised by the Soprintendenza Archeologia of Tuscany, encountered a stratified succession of alternating lacustrine and colluvial deposits. Seven stratigraphic units have been recognized, named U 1–U 7 from the bottom upward, most of which are mudstones, more or less calcareous, deposited during successive lake-level fluctuations. The succession is confined within a quite narrow, east/west-trending depression that formed a shallow embayment carved into older alluvial beds. U 1 consists of 60 cm of marginal lacustrine mudstone. An erosional surface separates it from U 2, a paleosurface formed with low sediment input. U 2 contains the oldest anthropic evidence of the site, represented by stone tools and wooden sticks, interspersed with bones of large vertebrates, especially P. antiquus. Typologically, the stone artifacts (about 200) of U 2 are only broadly indicative of an early Middle Paleolithic age. Several tens of tiny flakes are interpreted as possible byproducts of a retouching activity that took place on site. Wooden artifacts found on the paleosurface U 2 were mostly concentrated in a relatively small area (some 17 m² wide) at the western end of the excavation. They were all horizontally and randomly oriented, and in contact with the elephant remains. Some of them were found even under the bones. The poor state of preservation of the wooden artifacts rendered their recovery and following analysis very difficult.

Thermal activity affected this marginal lake area already between U 1 and U 2, and grew progressively stronger from U 3 and U 4 onward. U 4 has been radiometrically U-dated to 171 ± 3 ka based on pisoliths and electron spin resonance/U-series–dated to 170 ± 13 ka on a left lower molar of Bos primigenius. These radiometric datings indicate that the Poggetti Vecchi succession accumulated during a time spanning the latest MIS7 interglacial and whole MIS6 glacial, when the climate was globally deteriorating. Subsequent to U 4, the lake level dropped and then rose again. This led to the depositional and ecological conditions indicated by U 6, when organic-rich mudstones settled in the Poggetti Vecchi depression. A few wooden artifacts were found at the base of U 6, and therefore possibly accumulated on the lake bottom. From the paleoenvironmental viewpoint, the fossil mammals are suggestive of extensive open grasslands inhabited by large grazers, such as P. antiquus and B. primigenius. The red deer Cervus elaphus and the roe deer Capreolus capreolus browsed in sparse groves. The different kinds of herbaceous plant pollen, particularly of Poaceae, which dominates the spectra along all of the stratigraphic succession, indicate that the site was surrounded by a highly diverse grassland. Hygro- and hydrophytes attest to the presence of wetlands in the plain and in proximity to the site. Tree pollen is scanty, and Buxus pollen is also present. Pollen grains from U 1, from the top of U 2, and from U 6 reveal an abundance of freshwater ferns but also a high variety of wetland plants, which confirms the indications of the periodic occurrence of freshwater bodies and seeps given by the mollusk and ostracod assemblages.

Fifty-eight wooden remains (46 from the paleosurface U 2 and 12 from U 6), ranging in size from a few centimeters to over 1 m, were found at Poggetti Vecchi. Buxus sempervirens L. (boxwood) is the predominant wood at the site (47 of the 55 identified items). The remaining eight wooden fragments are of deciduous oak (Quercus sp.), ash (Fraxinus sp.), juniper (Juniperus sp.), and Populus/Salix. They likely derive from the local vegetation. Thirty-nine boxwood items have been identified as tools showing clear evidence of human manufacturing. Straight branches were intentionally selected; small lateral branches were carefully removed, and the bark was scraped off. The manufacture is also testified to by the presence of traces on the wooden surfaces: cut marks near lateral branches and striations along the shaft.

Some of them have the ends worked in the shape of a blunt point or a handle, and can hence be defined as sticks. A “stick” is commonly a roughhewn branch, around 1 m long and with a diameter such that it can be easily gripped in the hand and employed for different purposes. All of the sticks were made from straight branches with a diameter from 2.5–4 cm. The natural tapering shape of the branches was used to fashion a point at the thinner end (diameter of about 1.5 cm) and a rounding edge that we call a “handle” at the thicker end.

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The artifacts are almost all incomplete and display various types of fracturing. Some reveal the characteristic fraying of the fibers produced ab antiquo on the intact wood, while other clear-cut fractures were made in a subsequent phase on already decayed wood and can be attributed partly to sediment pressure and partly to the exposure of the wood during excavation.

The micromorphological appearance of the wood indicates profound decay caused by bacterial attack, clearly visible at fiber level. The fiber cell wall was thinned by the digestion of the polysaccharidic structural component, mostly the cellulose. The degree of decay is between class III and IV, according to the sample. The reduction of the amount of cellulose is confirmed by the appearance of the wood fractures, which are neat and not fibrous as in sound wood.

The macromorphological features of the superficial layers of the sticks revealed the absence of bark. The surfaces of 12 sticks appear partially blackened. One of them (stick 49b) shows a black superficial layer, about 1 mm thick, dissected by numerous cuboid fractures typical of wood charring. The other sticks have a black surface layer thinner than that of the previous one; this layer appears smoothed and, in any case, is distinctly different from the wood beneath.

To assess the nature of the blackening, some black samples from sticks 2, 3, 9, 11, 49b, and 50 were subjected to an oxidative reaction using hydrogen peroxide. This test indicated that the Poggetti Vecchi samples were charred since they remained unchanged, unlike humified wood, which decomposes and becomes lighter.

Moreover, the micromorphological analysis of the black surface layer of two blackened items (sticks 9 and 49b) reveals the anatomical features of charred boxwood. The cell walls are thinner than normal and glossy and compact; the loss of the typical multiple-layered feature (composite middle lamella and secondary cell wall laminated in turn) makes them homogeneous, although the anatomical structure maintains the diagnostic characteristics for wood identification.

The microscopic SEM observations of the black layer also revealed the increased porosity due to pyrogenic expulsion of combustion-generated gas and wood shrinkage due to the transformation of the polysaccharide component during charring.

All these points clearly indicate that some wooden tools were superficially charred.

The artifacts of Poggetti Vecchi are unique in being much shorter than wooden spears, in being made from boxwood, and in having handles that show a combination of morphological and functional traits, unknown so far. These features suggest that the artifacts of Poggetti Vecchi were used for a different purpose and not as throwing weapons.

All in all, the morphometric characteristics of the Poggetti Vecchi wooden tools (rounded handles, blunt points, and dimensions) recall those of the so-called digging sticks. These tools are commonly part of the daily life equipment of foragers.

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Some of the sticks reveal a more or less continuous blackening of the surface. The analysis of some of these tools (nos. 2, 3, 9, 11, 49b, and 50) demonstrated that this blackening is due to the action of fire. The burning affects a very superficial portion of the shaft (maximum of 1 mm). The other blackened exemplars also reveal a film of similar appearance and depth, so that it can be assumed that for these artifacts too, it was due to burning.

The decisive elements in favor of intentional burning are as follows:

The recurrent localization of the burning along the shaft but not at the ends (tips and handles), where it has been removed in the working. The absence of burning on the tips rules out the use of the tool in the fire (e.g., as a skewer), and hence accidental burning.

The traces of working (scratches and cut marks) on the burnt surfaces, proving that the use of fire was a phase in the process of fabrication of the digging sticks.

The uniform and reduced thickness of the blackened film. Only a controlled exposure to the action of the fire can produce this type of result. Experimentation has, in fact, shown that the exposure to fire of the wooden artifacts has to be constantly controlled to avoid excessive and inhomogeneous carbonization.

The Poggetti Vecchi sticks therefore provide evidence of the use of fire for working wooden implements by an early Neanderthal population.

(Source: “Wooden tools and fire technology in the early Neanderthal site of Poggetti Vecchi (Italy)”, by Biancamaria Aranguren et al.)

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Research-Selection for NovoScriptorium: Philaretus Homerides

 

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