ESR DATING AN OLDOWAN SITE IN DAGESTAN, SOUTHERN RUSSIA: EXPLORING THE EARLIEST HOMINID MIGRATION INTO EURASIA

Ainikab I contains 13 layers in four geological units. The lowermost gravel-rich layers yielded typical Oldowan choppers, adzes, and picks associated with Apsheronian (= Upper Villafranchian) pollen, Equus stenonis, and 13 other extinct faunal species. The Himalayas-Caucasus-Alps-Pyrénées Mt. barrier was thought to inhibit early hominid migration, by separating subtropical and tropical Mediterranean and African, from temperate and subarctic northern European and Asian, climates. The site’s location north of this barrier hints that hominids had made significant adaptations in order to exploit its colder environment. At Ainikab I, pollen and fauna indicate a broad-leafed forest with patches of mixed forest locally, growing under a climate that fluctuates from drier and cooler to warmer and moister. From sedimentary paleomagnetism, the mildly cemented lower unit, which contains lenses of siltier sediment, predates the Jaramillo Subchron (0.99-1.07 Ma).

Two equid teeth from Layers 10 and 11 in the lowermost unit were dated by standard and isochron ESR. Their enamel U concentrations indicate recent or secondary U uptake. High dentinal U concentrations hint that the teeth experienced exposure to saline groundwater. Assuming linear U uptake, the standard ESR ages averaged 852 ± 27 ka, but significant variation in the accumulated doses suggests that this is a minimum age. Isochron analysis indicates that recent U uptake at ~ 330 ± 50 ka affected the tooth. Therefore, the best estimate for the tooth’s age, assuming a multistage U uptake model, is ~ 1.5 ± 0.3 Ma. More teeth from Ainikab need to be dated to ensure that its deposits have not experienced reworking. An equid tooth from Layer 10 gave preliminary ages > 1 Ma. Hence, by the Early Pleistocene, probably sometime during Oxygen Isotope Stage 50 to 65, hominids had migrated north of the Caucasus Mountains.