Constraining the chronology and ecology of Late Acheulean and Middle Palaeolithic occupations at the margins of the monsoon

Abstract

South Asia hosts the world's youngest Acheulean sites, with dated records typically restricted to sub-humid landscapes. The Thar Desert marks a major adaptive boundary between monsoonal Asia to the east and the Saharo-Arabian desert belt to the west, making it a key threshold to examine patterns of hominin ecological adaptation and its impacts on patterns of behaviour, demography and dispersal. Here, we investigate Palaeolithic occupations at the western margin of the South Asian monsoon at Singi Talav, undertaking new chronometric, sedimentological and palaeoecological studies of Acheulean and Middle Palaeolithic occupation horizons. We constrain occupations of the site between 248 and 65 thousand years ago. This presents the first direct palaeoecological evidence for landscapes occupied by South Asian Acheulean-producing populations, most notably in the main occupation horizon dating to 177 thousand years ago. Our results illustrate the potential role of the Thar Desert as an ecological, and demographic, frontier to Palaeolithic populations.

Figure 1

Maps highlighting the location of Singi Talav in relation to (left) key South Asian Acheulean sites [Data: SRTM (NASA)], (top right) and illustrating its position within semi-arid landscapes at the margin of the monsoon (Data: WorldClim.org) with respect to other dated Palaeolithic sites in the Thar Desert region, (bottom right) with the location of SGT6 and SGT7 illustrated with respect to the 1981–85 excavation site and key landscape features [Data: ALOS (JAXA)] [Maps produced using ArcMap 10.5 (https://www.esri.com)]. Notably, the Singi Talav basin is separated from the adjacent Didwana salt lake basin by a linear dune formed within a break in the Balia hills; the excavation at 16R Dune exposes the depositional sequence of this dune, demonstrating ~ 18 m sand dune accumulation has occurred here beginning from ~ 187 ka.

Figure 2

Sediment sequences exposed at Singi Talav [SGT6 (top) and SGT7 (bottom)], synthesising (from left to right) results of geochronology, section photo, sediment log (illustrating the location of dating samples), identification of layers, grain size summary statistics, magnetic susceptibility, loss on ignition results differentiating between alternate organic components, and between total organics (TOC) and carbonates, geochemical weathering indices (CIA; WIP), results of stable isotope analyses on carbonate nodules, and phytolith analysis (for SGT7 only). Layers 6*, 7* and 8* at SGT7 are broadly comparable to previous reports, but we use this notation in identification of some minor differences, whereas all other layers provide a direct match to previous reports. See SI3 and SI6 for further description and datasets.

Figure 3

Artefacts recovered during new investigations at Singi Talav, including (a) multi-platform core (Layer 2); (b) bifacially retouched flake (Layer 3); (c) discoidal core (Layer 4); (d) biface with invasive removal (eroding from quarry edge); (e) finely retouched flake (eroding from quarry edge).

Figure 4

High altitude cave speleotherm (a: Bittoo Cave [India]) and marine core records from the Arabian Sea (b: MD04; c: Owen Ridge) and Bay of Bengal (d: Site 758) illustrating patterns of monsoonal variability spanning the occupations of Singi Talav (SGT6: dark green; SGT7: light green) and major phases of cultural activity in South Asia including Late Palaeolithic (yellow) and Middle Palaeolithic (dark blue), Attirampakam Middle Palaeolithic (light blue [NB only two assemblages present]), and Late Acheulean (red)^,,. Phases of lacustrine deposition at Singi Talav are associated with both prominent peaks and troughs of monsoonal intensity during glacial phases (MIS 8, 6 and 4) evident in Arabian Sea records, highlighting the importance of terrestrial proxy records to understand how wider patterns of climatic flux may have been manifest in landscapes occupied by Palaeolithic hominins.

Figure 5

Hierarchical bifacial cores reported from Singi Talav assemblages Layer 3 (a) and Layer 4 (b–e) (redrawn from ).