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The modern human hand is an intriguing mix of primitive morphology and derived function. Traditionally, its form and function are explained as a functional "trade‐off" between the requirements of locomotion and manipulation, but recently acquired comparative, experimental and fossil evidence suggests that this functional trade‐off is more complex than conventional wisdom suggests. Moreover, when studying hand evolution within the hominin clade, the only morphological evidence comes from the hard‐tissues, and evidence about hand function must be inferred indirectly from the archaeological record. We lack information about critical aspects of hand form (e.g., soft tissues) and function (e.g., neurology) as well as non‐lithic evidence about behavior. Thus, comparative anatomical, experimental and ethological studies of modern humans and other primates are critical to making more informed inferences about hand use in the past. We review the relevant fossil and archaeological evidence within the relevant comparative context (e.g., other extant apes and dexterous monkeys) in an attempt to reconstruct hand evolution within the hominin clade. We conclude by summarizing our current understanding—or lack thereof—of the evolutionary history of the modern human hand. [ABSTRACT FROM AUTHOR]

Body mass is a critical variable in many hominin evolutionary studies, with implications for reconstructing relative brain size, diet, locomotion, subsistence strategy, and social organization. We review methods that have been proposed for estimating body mass from true and trace fossils, consider their applicability in different contexts, and the appropriateness of different modern reference samples. Recently developed techniques based on a wider range of modern populations hold promise for providing more accurate estimates in earlier hominins, although uncertainties remain, particularly in non‐Homo taxa. When these methods are applied to almost 300 Late Miocene through Late Pleistocene specimens, the resulting body mass estimates fall within a 25–60 kg range for early non‐Homo taxa, increase in early Homo to about 50–90 kg, then remain constant until the Terminal Pleistocene, when they decline. [ABSTRACT FROM AUTHOR]

Author(s): C. Ashley Norris [1]; Bernard J. Wood (corresponding author) [1] The silicate Earth is strongly depleted in moderately volatile elements (such as lead, zinc, indium and alkali elements) relative [...]

Smith and Wood reply to Villmoare and Kimbel regarding the scientific credibility of problems in paleoanthropology that require causal explanations for unique historical events. [ABSTRACT FROM AUTHOR]

We have performed experiments at 1.5 GPa and 1400 °C on 25 different bulk compositions to determine the effects of major element compositions on the Cl contents of silicate melts at known fugacities of Cl2 and O2. The experimental method involved mixing a "sliding" Cl buffer, a mixture of AgCl, AgI, and Ag with the silicate bulk composition and performing the experiment in a graphite capsule together with a source of CO2 (AgCO3). The graphite capsules were sealed inside welded Pt tubes to maintain a CO2-CO atmosphere with oxygen fugacity fixed at the C-CO-CO2 (CCO) buffer. During the experiment, the Cl buffer segregates leaving a Cl-bearing melt, which quenches to a glass. We used the results to define chloride capacity CCl for each melt at the pressure and temperature of the experiment: C C l = C l (w t f C l 2 × f O 2 4 Chloride capacity was found to correlate positively with optical basicity and NBO/T and negatively with ionic porosity and the Larsen index. We combined our new data with the results of Thomas and Wood (2021) to derive an equation describing the composition, pressure and temperature dependence of the chloride capacity: log C C l = 1.601 + 4470 X C a − 3430 X S i + 2592 X F e − 4092 X K − 894 P / T. In this equation, XCa, XSi, and so on refer to the oxide mole fractions on a single-cation basis, P is in GPa and T in K. The equation reproduces 58 data points with an r2 of 0.96 and a standard error of 0.089. The addition of literature data on hydrous experiments indicates that the effects of <4.3 wt% H2O are small enough to be ignored. We also performed experiments aimed at determining the conditions of NaCl saturation in melts. When combined with literature data we obtained: log C l − = log a N a C l + 0.06 − 2431 X C a + 3430 X S i − 2592 X F e + 3484 X N a + 4092 X K − 2417 / T where (Cl–) is the Cl content of the melt in wt% aNaCl is the activity of NaCl (liquid) and the other symbols are the same as before. The results indicate that basalt dissolves ~8 times more Cl than rhyolite at a given NaCl activity i.e., Cl is ~8 times more soluble in basalt than in rhyolite. [ABSTRACT FROM AUTHOR]