Hamdallah Bearat

Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia

The oldest direct evidence of stone tool manufacture comes from Gona (Ethiopia) and dates to between 2.6 and 2.5 million years (Myr) ago. At the nearby Bouri site several cut-marked bones also show stone tool use approximately 2.5 Myr ago. Here we report stone-tool-inflicted marks on bones found during recent survey work in Dikika, Ethiopia, a research area close to Gona and Bouri. On the basis of low-power microscopic and environmental scanning electron microscope observations, these bones show unambiguous stone-tool cut marks for flesh removal and percussion marks for marrow access. The bones derive from the Sidi Hakoma Member of the Hadar Formation. Established 40Ar–39Ar dates on the tuffs that bracket this member constrain the finds to between 3.42 and 3.24 Myr ago, and stratigraphic scaling between these units and other geological evidence indicate that they are older than 3.39 Myr ago. Our discovery extends by approximately 800,000 years the antiquity of stone tools and of stone-tool-assisted consumption of ungulates by hominins; furthermore, this behaviour can now be attributed to Australopithecus afarensis.

Tool-marked bones from before the Oldowan change the paradigm

Dominguez-Rodrigo et al. (1) critiqued our paper (2), which provided the earliest evidence for stone tool use and animal tissue consumption as evidenced by bones bearing tool-induced marks found at DIK-55 (Dikika, Ethiopia) and dated to 3.39 Ma. Applying a configurational approach, they questioned the bones’ context and without examining or conducting new analysis on the original fossils, argued that all of the Dikika marks resulted from trampling, because a small subset of these marks superficially resembled a small subset of experimentally trampled specimens. Furthermore, they argued (1) that stone tool use and meat consumption before the current consensus dates requires finding manufactured … [↵][1]1To whom correspondence should be addressed. E-mail: mcpherron{at}eva.mpg.de. [1]: #xref-corresp-1-1

In-situ nanoscale observations of the Mg(OH)2 dehydroxylation and rehydroxylation mechanisms

Environmental transmission electron microscopy has been used to probe the mechanisms that govern Mg(OH)2 dehydroxylation and rehydroxylation processes at the near-atomic level. Dehydroxylation and rehydroxylation rates for these in-situ observations were controlled by regulating the water vapour pressure over the sample. Generally, the dehydroxylation proceeded via the nucleation and growth of an oxide lamella, resulting in the formation of oxide and/or oxyhydroxide regions within the reaction matrix. Competition between rapid-nucleation–slow-growth and slow-nucleation–rapid-growth mechanisms can dramatically impact the nanostructure formed during dehydroxylation. Steps, both parallel and perpendicular to the {0001} planes, were observed to form during dehydroxylation. The nanocrystalline MgO formed was highly reactive and readily rehydroxylated with increasing water vapour pressure. Rehydroxylation proceeded via the nucleation and growth of Mg(OH)2 crystals in the heavily dehydroxylated matrix. The partial edge dislocations formed (both parallel and perpendicular to {0001}brucite) as the result of Mg(OH)2 nanocrystal intergrowth and anneal out with time, resulting in the formation of relatively large single crystals of Mg(OH)2. Such high mobility of Mg-containing species during rehydroxylation can be directly associated with the high chemical reactivity observed during rehydroxylation, which can facilitate key reaction processes, such as CO2 mineral sequestration.

Late Byzantine-Early Islamic Ceramic Technology, Transjordan

Administratively, the territories of Transjordan (a neutral term for what is now Jordan) have always belonged to different provinces. During the Late Byzantine or Early Islamic periods, the administrative borderlines were imposed by geographic rather than political considerations. They were generally running from east to west (Hitti 1970; Watson 2001). Hence, we can distinguish three major regions in Transjordan: northern, central and southern. While the northern one certainly had privileged relations with north Palestine and Syria, the central region had close relations with Palestine, and the southern played an important role in relations with south Arabia and Egypt. In times of peace as well as in times of war, Transjordan has therefore played an important role as a platform for trade and warfare in both north-south and east-west directions.

ATOMIC-LEVEL IMAGING OF CO2 DISPOSAL AS A CARBONATE MINERAL: OPTIMIZING REACTION PROCESS DESIGN

Fossil fuels, especially coal, can support the energy demands of the world for centuries to come, if the environmental problems associated with CO{sub 2} emissions can be overcome. Permanent and safe methods for CO{sub 2} capture and disposal/storage need to be developed. Mineralization of stationary-source CO{sub 2} emissions as carbonates can provide such safe capture and long-term sequestration. Mg(OH){sub 2} carbonation is a leading process candidate, which generates the stable naturally occurring mineral magnesite (MgCO{sub 3}) and water. Key to process cost and viability are the carbonation reaction rate and its degree of completion. This process, which involves simultaneous dehydroxylation and carbonation is very promising, but far from optimized. In order to optimize the dehydroxylation/carbonation process, an atomic-level understanding of the mechanisms involved is needed. Since Mg(OH){sub 2} dehydroxylation is intimately associated with the carbonation process, its mechanisms are also of direct interest in understanding and optimizing the process. In the first project year, our investigations have focused on developing an atomic-level understanding of the dehydroxylation/carbonation reaction mechanisms that govern the overall carbonation reaction process in well crystallized material. In years two and three, we will also explore the roles of crystalline defects and impurities. Environmental-cell, dynamic high-resolution transmission electron microscopy has been used to directly observe the dehydroxylation process at the atomic-level for the first time. These observations were combined with advanced computational modeling studies to better elucidate the atomic-level process. These studies were combined with direct carbonation studies to better elucidate dehydroxylation/carbonation reaction mechanisms. Dehydroxylation follows a lamellar nucleation and growth process involving oxide layer formation. These layers form lamellar oxyhydroxide regions, which can grow both parallel and perpendicular to the Mg(OH){sub 2} lamella. The number of oxide layers within the regions increases as they grow during dehydroxylation. Selected area diffraction suggests a novel two-dimensional variant of Vegards law can describe the oxyhydroxide regions, with intralamellar Mg-Mg packing distances observed between those known for Mg(OH){sub 2} and MgO. Intralamellar and interlamellar elastic stress induced during dehydroxylation can contribute to crystallite cracking and MgO surface reconstruction, which may serve to enhance carbonation reactivity. The observed dehydroxylation process indicates a range of candidate materials for carbonation may be present during the carbonation process (i) the hydroxide, (ii) a range of intermediate oxyhydroxides, and (iii) the oxide, potentially in more-reactive, very small particle size form. Partial carbonation of single-crystal Mg(OH){sub 2} fragments over a wide range of reaction conditions (varying CO{sub 2} pressure and temperature) shows a linear or near-linear correlation between carbonation and dehydroxylation, with the extent of dehydroxylation substantially greater than the extent of carbonation. This suggests carbonation primarily occurs via intermediate oxyhydroxide or oxide formation. The range and type of intermediate oxyhydroxides/oxides that can form in advance of carbonation should provide a degree of control over both their formation and the overall reactivity observed for the carbonation process.