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People often enjoy reading about where humans come from and how we developed into the unusual creatures we are today: upright-walking, omnivorous mammals who inhabit every continent (and who enjoy [...]

Millimeter‐to‐nanometer‐sized iron‐ and nickel‐rich metals are ubiquitous on the lunar surface. The proposed origin of these metals falls into two broad classes which should have distinct geochemical signatures—(1) the reduction of iron‐bearing minerals or (2) the addition of metals from meteoritic sources. The metals measured here from the Apollo 16 regolith possess low Ni (2–6 wt%) and elevated Ge (80–350 ppm) suggesting a meteoritic origin. However, the measured Ni is lower, and the Ge higher than currently known iron meteorites. In comparison to the low Ni iron meteorites, the even lower Ni and higher Ge contents exhibited by these lunar metals are best explained by impact‐driven volatilization and condensation of Ni‐poor meteoritic metal during their impact and addition to the lunar surface. The presence of similar, low Ni‐bearing metals in Apollo return samples from geographically distant sites suggests that this geochemical signature might not be restricted to just the Apollo 16 locality and that volatility‐driven modification of meteoritic metals are a common feature of lunar regolith formation. The possibility of a significant low Ni/high Ge meteoritic component in the lunar regolith, and the observation of chemical fractionation during emplacement, has implications for the interpretation of both lunar remote‐sensing data and bulk geochemical data derived from sample return material. Additionally, our observation of predominantly meteoritic sourced metals has implications for the prevalence of meteoritic addition on airless planetary bodies. [ABSTRACT FROM AUTHOR]

Have you ever wondered whether your own family history is more interesting and exotic than you think? Might you have a long-lost relative who was a circus performer, a pirate, [...]

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 [...]

The article focuses on the ontogeny of craniofacial development in the Pleistocene robust australopith Paranthropus robustus, based on fossils from the sites of Kromdraai and Drimolen. It mentions the study reveals insights into the timing and characteristics of craniofacial features in P. robustus infants, suggesting potential relationships with early Homo and challenging previous taxonomic attributions.

Yet, despite his call for a more speciose interpretation of early I Homo i , in the illustration early in the book illustrating fossil hominin species through time, Tattersall lumps all the eastern African early I Homo i fossils into a single species. Despite the prodigious efforts of field researchers, the fossil evidence we have now (i.e. the "known fossil record" sensu [1]) is almost certainly much less informative about taxic diversity, geographical range, and temporal span, than the fossil record we imagined in our thought experiment. Researchers who recently tried to estimate the impact of rock availability and collection effort on the first and last appearances of early fossil hominin taxa came to the conclusion that these two factors likely had a profound influence on whether a taxon left an accessible fossil record ([4]). There are cases when one new fossil (e.g. OH 7, the type specimen of I Homo habilis i from Olduvai [now Oldupai] Gorge in Tanzania) is so different from the existing fossil evidence at a site (e.g. OH 5, the type specimen of I Paranthropus boisei i , also from Olduvai Gorge) that the case for taxonomic distinctiveness is obvious, but not many claims for new hominin taxa are as securely based as this example. [Extracted from the article]

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]

Recent [sup.142]Nd isotope data indicate that the silicate Earth (its crust plus the mantle) has a samarium to neodymium elemental ratio (Sm/Nd) that is greater than that of the supposed chondritic building blocks of the planet. This elevated Sm/Nd has been ascribed either to a 'hidden' reservoir in the Earth (1,2) or to loss of an early-formed terrestrial crust by impact ablation (3). Since removal of crust by ablation would also remove the heat-producing elements--potassium, uranium and thorium--such removal would make it extremely difficult to balance terrestrial heat production with the observed heat flow (3). In the 'hidden' reservoir alternative, a complementary low-Sm/Nd layer is usually considered to reside unobserved in the silicate lower mantle. We have previously shown, however, that the core is a likely reservoir for some lithophile elements such as niobium (4). We therefore address the question of whether core formation could have fractionated Nd from Sm and also acted as a sink for heat-producing elements. We show here that addition of a reduced Mercury-like body (or, alternatively, an enstatite-chondrite-like body) rich in sulfur to the early Earth would generate a superchondritic Sm/Nd in the mantle and an [sup.142]Nd/[sup.144]Nd anomaly of approximately +14 parts per million relative to chondrite. In addition, the sulfur-rich core would partition uranium strongly and thorium slightly, supplying a substantial part of the 'missing' heat source for the geodynamo., Terrestrial rocks were recently found to have higher ratios of radiogenic [sup.142]Nd to nonradiogenic [sup.144]Nd than do the chondritic meteorites generally supposed to be representative of the material from which [...]