Identification of the earliest collagen- and plant-based coatings from Neolithic artefacts (Nahal Hemar cave, Israel)

Abstract

Mortuary practices in human evolution record cognitive, social changes and technological innovations. The Neolithic Revolution in the Levant was a watershed in this domain that has long fascinated the archaeological community. Plaster modelled skulls are well known at Jericho and several other Neolithic sites, and in Nahal Hemar cave (Israel, ca. 8200 −7300 cal. BC) excavations yielded six unique human skulls covered with a black organic coating applied in a net pattern evoking a headdress. This small cave was used as storage for paraphernalia in the semi-arid area of the Judean desert and the dry conditions preserved other artefacts such as baskets coated with a similar dark substance. While previous analysis had revealed the presence of amino acids consistent with a collagen signature, in the present report, specific biomarkers were characterised using combined proteomic and lipid approaches. Basket samples yielded collagen and blood proteins of bovine origin (Bos genus) and a large sequence coverage of a plant protein charybdin (Charybdis genus). The skull residue samples were dominated by benzoate and cinnamate derivatives and triterpenes consistent with a styrax-type resin (Styrax officinalis), thus providing the earliest known evidence of an odoriferous plant resin used in combination with an animal product.

The potential of triterpenoids as chemotaxonomic tools to identify and differentiate genuine, adulterated and archaeological balsams

“…8200 −7300 cal. BC) [16]. It thus appears that reliable chemotaxonomic criteria based, in particular, on lipid markers allowing unambiguous identification of archaeological balsams are desirable and have to be established.…”

“…Previous molecular studies of balsams, reviewed by Pauletti et al [7] and Custódio and Veiga-Junior [2], were however mainly dedicated to fresh material and focused on the characterisation of volatile and fragrant compounds, comprising monoterpenoids and ester derivatives of cinnamic, benzoic, p-coumaric and ferulic acids in S. benzoin [15,[17][18][19][20], S. paralleloneurum [9,19], S. tonkinensis [9,20], L. styraciflua [21], L. orientalis [9,[21][22][23] and Myroxylon pereirae [24] and some specificity of the distributions of these compounds with respect to their source could be evidenced. Nevertheless, in the case of archaeological balsams, these compounds cannot be easily used to recognise the nature of the plant species since they are prone to alteration, as illustrated by the case of the balsam identified on the skull of the Nahal Hemar cave [16]. In the latter case, the distributions of the cinnamic and benzoic acid derivatives, although useful to relate the substance on the skull to a balsam-type resin, were too altered to allow a distinction to be made between a resin from S. officinalis and L. orientalis -the two possible botanical sources in the eastern Mediterranean region -.…”

“…constituents of the organic substance on the skull [16]. In addition, the predominant cinnamic and benzoic esters in balsams are potentially prone to hydrolysis and, similarly to unsaturated fatty acids [e.g.…”

“…As far as we know, since its characterisation by Ulubelen et al [42] in the aerial parts of S. officinalis, styraxin 42 has not been reported to occur in other Styrax species and in any other plants. Hence, styraxin 42 could represent a specific marker of S. officinalis and could be used as an indicator for the use of S. officinalis resin in an archaeological context, as attested by its identification in an 8000 years-old decorated skull [16].…”

“…Intermolecular esterification reactions may also occur during ageing processes, leading to the neoformation of cinnamate and benzoate derivatives absent from fresh balsams. For instance, such a possibility may explain the presence of a number of high molecular weight ester derivatives of cinnamic and benzoic acids detected in a 8000-years old organic coating from a decorated human skull [16]. Following these considerations, ester derivatives of cinnamic and benzoic acids on their own are not reliable markers to allow a clear discrimination to be made between balsams, notably in the case of ancient material unearthed at archaeological sites.…”