Investigating the Signature of Aquatic Resource Use within Pleistocene Hominin Dietary Adaptations

Abstract

There is general agreement that the diet of early hominins underwent dramatic changes shortly after the appearance of stone tools in the archaeological record. It is often assumed that this change is associated with dietary expansion to incorporate large mammal resources. Although other aspects of the hominin diet, such as aquatic or vegetal resources, are assumed to be a part of hominin subsistence, identifying evidence of these adaptations has proved difficult. Here we present a series of analyses that provide methodological support for the inclusion of aquatic resources in hominin dietary reconstructions. We suggest that bone surface modifications in aquatic species are morphologically distinguishable from bone surface modifications on terrestrial taxa. We relate these findings to differences that we document in the surface mechanical properties of the two types of bone, as reflected by significant differences in bone surface microhardness values between aquatic and terrestrial species. We hypothesize that the characteristics of bone surface modifications on aquatic taxa inhibit the ability of zooarchaeologists to consistently diagnose them correctly. Contingently, this difficulty influences correspondence levels between zooarchaeologists, and may therefore result in misinterpretation of the taphonomic history of early Pleistocene aquatic faunal assemblages. A blind test using aquatic specimens and a select group of 9 experienced zooarchaeologists as participants was designed to test this hypothesis. Investigation of 4 different possible explanations for blind test results suggest the dominant factors explaining patterning relate to (1) the specific methodologies employed to diagnose modifications on aquatic specimens and (2) the relative experience of participants with modifications on aquatic bone surfaces. Consequently we argue that an important component of early hominin diets may have hitherto been overlooked as a result of (a) the paucity of referential frameworks within which to identify such a component and (b) the inability of applied identification methodologies to consistently do so.

Cut marks on bone surfaces: influences on variation in the form of traces of ancient behaviour

“…It was previously understood that bone surface properties impacted surface modifications [17,19]. This is easily taken into account when analysing cut marks (as long as the bone portion is often recognizable on the archaeological specimen).…”

“…This is critical to understand how hominin diet changed through time because the morphology of cut marks may be able to provide information about the timing of access to carcasses [16]. While palaeoanthropologists have come a long way in answering this call to relate static traces of the past to the dynamic processes that created them we remain largely unaware of the mechanical factors that affect the morphology of bone surface modifications [17]. A more detailed understanding of the nature of cut-mark formation is necessary because numerous biostratinomic factors are likely to have an influence on the mechanical properties of bone.…”

Taphonomy of fossils from the hominin-bearing deposits at Dikika, Ethiopia

“…The Basal Member locality of DIK-58 had the highest proportions of more heavily-rounded specimens, followed closely by the Sidi Hakoma Member localities DIK-49 and DIK-50. Some of the edge rounding data may be affected by the proportions of fish in the assemblage, as fish bone fragments are generally smaller and harder than mammal bone (Archer and Braun, 2013). When fish are removed from analysis, the lack of edge rounding at DIK-42 and DIK-43 remains apparent, while the variability in rounding classes at the other localities becomes more prominent (Fig.…”

Assessment of statistical agreement of three techniques for the study of cut marks: 3D digital microscope, laser scanning confocal microscopy and micro‐photogrammetry

“…Techniques based on microimages are essential in order to get high‐resolution data that allow the identification of the type of tool or raw material used. In these studies, cut mark morphology analyses have been studied using different techniques, such as optic microscopy, hand lenses and scanning electronical microscope (SEM) and environmental scanning electron microscope (ESEM) (Shipman, ; Olsen, ; Greenfield, , , ,b; Smith & Brickley, ; Lewis, ; Blasco et al ., ), binocular microscope for high‐resolution pictures (Domínguez‐Rodrigo et al ., ; De Juana et al ., ; Marín‐Monfort et al ., ), digital imaging techniques (Gilbert & Richards, ), three‐dimensional (3D) reconstruction (During & Nilsson, ; Bartelink et al ., ; Kaiser and Katterwe, ), 3D digital microscope (Boschin & Crezzini, ; Crezzini et al ., ), Alicona 3D Infinite Focus Imaging microscope (Bello & Soligo, ; Bello et al ., ; Bello, ; Bonney, ), laser scanning confocal microscopy (LSCM) (Archer & Braun, ) or micro‐photogrammetric techniques (M‐PG) (Maté‐González et al ., , ).…”