FROM EAST TO NORTH-WEST AFRICA: MAGNETOCHRONOLOGY OF THE OLDEST AFRICAN ACHEULEAN SITES

In this thesis are presented the chronologies, obtained through magnetostratigraphy, of two key sites of archaeological and paleoanthropological interest, Melka Kunture (Upper Awas Valley, Ethiopia) and Thomas Quarry I (Casablanca, Morocco). These sites of Pleistocene age document the emergence and developments of the Acheulean lithic technology thought to be a major turning point in human evolution, representing over the last two decades a highly debated issue in the study of early technologies. In East Africa at Melka Kunture, located in the Ethiopian highlands, a time-diagnostic sequence of normal and reverse polarity magnetozones was obtained, representing a magnetochronologic record extending from the Brunhes Chron (<0.773 Ma) to the top of Reunion Subchron (2.116 Ma). The new data were then integrated with 40Ar/39Ar dating from the literature to establish age models of deposition that were used to estimate the mean ages of the main archeological levels contained. In North-West Africa at Thomas Quarry I, located in the outskirts of Casablanca (Morocco), magnetostratigraphy coupled with geochemistry provided a chronostratigraphic framework extending from the Brunhes Chron (<0.773 Ma) to the Matuyama pre-Cobb Mountain (>1.210 Ma) subchron. Research conducted in the last decade revealed that the Acheulean emergence in East Africa should have occurred around 1.7 Ma. This datum is testified by a few key archeological sites such as Kokiselei 4 (1.76 Ma; West Turkana, Kenya), KGA6-A1 (~1.75 Ma; Konso-Gardula, Ethiopia), FLK West (~1.7-1.65 Ma; Olduvai Gorge, Tanzania). The new magnetostratigraphic results obtained from Melka Kunture archeological area of Ethiopia pushed back the first occurrence of the Acheulean at 1.95 (-0.025; +0.1) Ma, some 200 ka before what previously known, and it also provided evidence of the earliest high-altitude peopling of East Africa at 2.02 (-0.095; +0.096) Ma. The peculiarity of the Acheulean as a cultural phenomenon lies in the first appearance of Large Cutting Tools (LCTs) representing the most evident novelty relative to the pre-existing Oldowan technology. However, the timing and modes of the technical innovation(s) leading to the Acheulean, their relationship with the pre-existing Oldowan technology and their dispersion across the African continent are still unclear. The age models established for Melka Kunture archeological area allowed also to date other more recent Acheulean sites documenting the continuity of this technology trough time, such as GAR XIIJ at 1.13 (-0.06; +0.05) Ma, GOM II OAM, yielding two fragmentary Homo heidelbergensis fossils (GOM II1-576 and GOM II1-6169), dated to 1.03±0.04 Ma and GOM II “Butchery site” at 0.75 (-0.1; +0.02) Ma. On the other hand, for the two sites GOM Iγ and GOM Iδ only minimum ages were proposed, respectively of ~1.41 and ~1.51 Ma, for lack of chronological constraints in their stratigraphic interval. Beginning from the new results from Melka Kunture, a chronostratigraphic record was assembled through a critical review of data from the literature of key archaeological and paleoanthropological sites from East Africa in order to infer about the dynamics of origin(s) and dispersal(s) of the Acheulean across the African continent, as well as the potential toolmaker(s) of this innovation. The reconstructed record spans between 2.0 and 1.6 Ma, across the Olduvai normal polarity subchron (1.925-1.770 Ma), which represents a fundamental magnetostratigraphic constraint in this field of research. The new data provided by this thesis suggest that in this time-interval, not one but several Acheulean techno-economic innovations appeared in the East African record emerging in a non-linear evolutionary path. This analysis suggests as novel scenario that there were several early Acheuleans that emerged in East Africa at different times, in different places and with different technical peculiarities derived from a common Oldowan background. As for Thomas Quarry I (Casablanca, Morocco), the age of ~1.3 Ma obtained for the archeological site ThI-L expanded our knowledge on the Acheulean emergence in Atlantic Morocco. This new age estimate based on magnetostratigraphy coupled to geochemistry makes the Acheulean of ThI-L the earliest of North-West Africa. The dynamics of dispersal and spreading of the Acheulean from its cradle in East Africa to North Africa are not yet clear because of the inherently discontinuous nature of the stratigraphic and archeological records. The wide gap between the Oldowan in Algeria, currently dated ~1.77 Ma, and the early Acheulean of Morocco, dated in this thesis at ~1.3 Ma, does not allow to infer about the origin of the early Acheulean of ThI-L but only further discoveries will clarify the emergence of the North African Acheulean in a whole pan-African perspective. Furthermore, the new data presented in this thesis allowed to constrain in time the site ThI-GH of Thomas Quarry I, located in a higher stratigraphic unit with respect to ThI-L, yielding Homo fossils associated to faunal remains and Acheulean tools. This site was constrained with magnetostratigraphy to the Brunhes/Matuyama boundary at 0.773±0.004 ka. The human remains from ThI-GH, currently under investigation, will shed light on the critical period of divergence between the Middle Pleistocene archaic lineages of Western Eurasia and Africa, one of which gave rise to the evolutionary line of Homo sapiens.