Evidence for humid and arboreal environment in the Middle Lisan Basin, 45-39 ka (the Mughr el-Hamamah site, Jordan): Implications for Anatomically Modern Human Dispersal into Western Eurasia

Abstract:

The period between 50-30 kya in western Eurasia witnessed Neanderthal extinction, anatomically modern human (AMH) expansion, and a transition from Middle to Upper Paleolithic material culture. The prevailing hypothesis suggests a replacement of the Neanderthal populations by incoming AMH population, perhaps involving climatic fluctuations that favored AMH biology and habitat preferences. Yet, new evidence questions the role of climate as a forcing factor in AMH dispersal from Africa, raising the possibility that AMH populations in southern Arabia were responsible for the <50 ka expansion into western Eurasia.

New excavations at Mughr el-Hamamah (MHM), Ajlun District, Jordan, uncovered a single well preserved occupational horizon. This horizon is dated by acid-base-wet oxidation/stepped combustion (ABOX-SC) AMS ¹⁴C assays to 45-39,000 cal BP and is associated with abundant diagnostic Early Upper Paleolithic (EUP) artifacts. The age of the site, combined with its excellent organic preservation, suggests that MHM can play a key role in testing hypotheses about the southern Levantine Rift Valley environment and EUP human adaptations to it.

This paper presents a paleoecological reconstruction derived from micromammal remains associated with in situ archaeological deposits in MHM. The assemblage is highly dominated by the Syrian squirrel (Sciurus anomalus), typical of cool and humid climate. It is common in Late Glacial fauna of the Mediterranean of the Levant, in sites such as Kebara UP and Amud. Yet, today it is known only from high elevation in Turkey, Syria and Jordan. Other taxa include several genera of murids, further supporting the reconstruction of woodland habitats within a 1-3 km radius around the site. Additional archaeological data confirm that MHM was situated along an ecotone between the forested, temperate plateau and the Jordan Valley bottom grassland. Dead Sea speleothems and stromatolites in Dead Sea escarpment caves, indicating a high stand of Lake Lisan ca. 40 ka, and suggesting an increase in humidity, are consisted with these results.

The ameliorate climate may have been a contributing factor for AMH dispersal into and out of the region. Thus, this Levantine rich ecozone would have "funneled" longer-distance mobility toward the Taurus-Zagros flanks, Mesopotamia and perhaps beyond.