The expansion of later Acheulean hominins into the Arabian Peninsula

www.nature.com/scientificreports OPEN Received: 27 July 2018 Accepted: 28 October 2018 Published: xx xx xxxx The expansion of later Acheulean hominins into the Arabian Peninsula Eleanor M. L. Scerri1,2, Ceri Shipton 3,4, Laine Clark-Balzan5, Marine Frouin2, Jean-Luc Schwenninger2, Huw S. Groucutt 1,2, Paul S. Breeze6, Ash Parton7,8, James Blinkhorn1,9, Nick A. Drake1,6, Richard Jennings10, Patrick Cuthbertson2, Abdulaziz Al Omari11, Abdullah M. Alsharekh12 & Michael D. Petraglia 1 The Acheulean is the longest lasting cultural–technological tradition in human evolutionary history. However, considerable gaps remain in understanding the chronology and geographical distribution of Acheulean hominins. We present the first chronometrically dated Acheulean site from the Arabian Peninsula, a vast and poorly known region that forms more than half of Southwest Asia. Results show that Acheulean hominin occupation expanded along hydrological networks into the heart of Arabia from Marine Isotope Stage (MIS) 7 until at least ~190 ka ̶ the youngest documented Acheulean in Southwest Asia. The site of Saffaqah features Acheulean technology, characterized by large flakes, handaxes and cleavers, similar to Acheulean assemblages in Africa. These findings reveal a climaticallymediated later Acheulean expansion into a poorly known region, amplifying the documented diversity of Middle Pleistocene hominin behaviour across the Old World and elaborating the terminal archaic landscape encountered by our species as they dispersed out of Africa. The Acheulean represents a key stage in hominin evolution, characterized by the production of large cutting tools such as handaxes for over ~1.5 million years1–5. Given the rarity of hominin fossils, mapping the chronological and geographic spread of the Acheulean is critical for reconstructing patterns of hominin expansion and evolution in different regions of the Old World. It is also crucial for defining the terminal Acheulean landscape encountered by hominins using Middle Palaeolithic technology, including Homo sapiens. However, considerable gaps remain in our understanding of the spatial and temporal distribution of the Acheulean. Currently, little is known about the Acheulean in the Arabian Peninsula, a critical region situated at the crossroads between Africa and Eurasia. Covering 3.2 million km2, the Arabian Peninsula has long been incorporated into narratives of early Eurasian colonization6 and numerous Acheulean sites with shared technological characteristics have been documented7–10. However, data required to refine and develop Acheulean dispersal hypotheses has been limited by the fact that the vast majority of documented sites are deflated surface sites lacking stratigraphy and chronometric age estimates. The only known stratified Acheulean site is Saffaqah, situated in the Dawadmi region of the Nejd plateau (Fig. 1). Saffaqah was first identified and excavated by Norman Whalen and colleagues in the 1980s11. Their 33 m2 excavation (Trench 1) resulted in the recovery of 8,395 buried artefacts. However, Whalen and colleagues11 did not discuss the stratigraphy nor artefact distributions within the excavations in any detail. They observed calcrete in Trench 1 from 30 cm downwards, while sterile sediment was reached 1 Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany. 2Research Laboratory for Archaeology and the History of Art, School of Archaeology, University of Oxford, 36 Beaumont Street, Oxford, OX1 2PG, UK. 3Centre of Excellence for Australian Biodiversity and Heritage, Australian National University, Canberra, Australia. 4British Institute in Eastern Africa, Nairobi, Kenya. 5Department of Geosciences, Freiburg, Germany. 6Department of Geography, Kings College London, London, UK. 7Human Origins and Palaeoenvironments Research Group, Department of Social Sciences, Oxford Brookes University, Headington Campus, Gipsy Lane, Oxford, OX3 0BP, UK. 8Mansfield College, University of Oxford, Oxford, OX1 3TF, UK. 9Department of Geography Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK. 10School of Natural Sciences and Psychology, Liverpool John Moores University, James Parsons Building, Byrom Street, Liverpool, L3 3AF, UK. 11Saudi Commission for Tourism and National Heritage, Riyadh, Saudi Arabia. 12Department of Archaeology, College of Archaeology and Tourism, King Saud University, Riyadh, Saudi Arabia. Correspondence and requests for materials should be addressed to E.M.L.S. (email: ) or M.D.P. (email: ) SCIEntIFIC REPOrTS | (2018) 8:17165 | DOI:10.1038/s41598-018-35242-5 1 www.nature.com/scientificreports/ Figure 1. Map showing locations of major river systems and Arabian sites noted in text (a); view of surrounding plain from the top of the andesite dyke: Trench 1 excavations are to the left of the jeeps (b). at depths of 1.33–1.49 m, and degrading granite bedrock at 1.62 m. Uranium-thorium ages on calcrete adhering to the artefacts suggested that the deposits were at least 200,000 years old, but the ages could not be considered secure (see Methods) and were not further refined. Given the importance of Saffaqah, a re-assessment of the site’s stratigraphy, archaeology and chronology was conducted by the Palaeodeserts Project in 2014 through re-excavation and extension of Trench 1, and a study of the surrounding landscape10. As reported here, new field investigations now also provide the first secure dates for what is still the only known stratified Acheulean site in the Arabian Peninsula. Results The Dawadmi region of central Saudi Arabia is characterized by a flat plain of Proterozoic igneous bedrock intruded by younger felsic and mafic dykes, and overlain in places by Quaternary aeolian and fluvial sediments. The climate is currently arid, although an intensification of the African Summer Monsoon and its incursion into Arabia brought increased summer rainfall to the Peninsula in the past12,13. Palaeoenvironmental records and climate model simulations indicate that increased humidity occurred during insolation maxima, in particular during interglacials and interstadials, such as those during Marine Isotope Stage 7 (MIS 7, ~240–190 ka) and the interstadials of MIS 5 (~130–75 ka)12,14. During these periods, the landscape of Arabia featured extensive river networks, lakes and wetlands with widespread vegetative increases. The Saffaqah site itself is situated near the Central Saudi Arabian town of Dawadmi. It is located beside the most prominent andesite dyke in the region, which rises ~60 m above the surrounding plain and is located on the northern flank of the dyke, below its highest point (Fig. 1). Our systematic survey revealed that Saffaqah is the largest Acheulean site yet documented in Arabia and is surrounded by a dense Acheulean landscape10,15. Palaeohydrological reconstruction demonstrated that the site sits at the interface between two major extinct river systems: the (...truncated)