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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]

We have determined the S contents of 14 different silicate melts equilibrated with Air/SO 2 mixtures at 1 atm pressure and temperatures of 1473–1773 K in 50 K intervals. Under these oxidizing conditions sulfur dissolves in the melts predominantly as sulfate (S6+ or SO 4 2–). The sulfur contents of the quenched products were determined by EPMA (Electron Probe Micro-Analysis) and by SIMS (Secondary Ion-Mass Spectrometry) with the latter being employed for low sulfur contents (i.e., ≤60 ppm). Equilibrium S contents were found to increase strongly with decreasing temperature and with some compositional parameters, especially CaO content. The data were used to calculate the sulfate capacity (log C S6+), for each melt composition at each temperature. Sulfate capacity is related to the equilibrium constant for sulfur dissolution and is defined as follows in terms of SO 4 2– concentration and fugacities of oxygen and sulfur: l o g C S 6 + = l o g SO 4 m e l t 2 - (w t. %) - 1 2 log fS 2 - 3 2 l o g fO 2 By determining log C S6+ at different Air/SO 2 ratios we showed that log C S6+ is independent of sulfur content and hence that Henry's Law is obeyed in the experimental composition and temperature range. We used stepwise linear regression to fit sulfate capacity to an equation incorporating compositional and temperature terms. Parameters which did not pass the F-test at the 95% confidence level were excluded. This approach led to the following fit equation: l o g C S 6 + = - 12.659 + (3692 X CaO - 7592 X SiO 2 - 13736 X TiO 2 + 3762 X Al O 1.5 + 34483) / T The standard error of the fit is 0.154 and R2 is 0.985. The data were used to simulate scenarios for SO 2 -degassing from ascending silicate melts of basaltic and andesitic compositions. The important observations are that SO 2 partitions strongly into an H 2 O-rich fluid phase and that most S is lost at relatively high pressures in the crust. So, for example we estimate that ≥85% of the initial S should be lost before the ascending magma reaches 100 MPa pressure. [ABSTRACT FROM AUTHOR]

• A new experimental method of controlling chlorine fugacity in silicate melts. • Chlorine dissolves by a mechanism in which 2 dissociated Cl− ions replace 1 O2− ion. • Chlorine remains stably dissolved in basalt to pressures <5 MPa. • Typical Cl 2 fugacities in basalt are ∼10−6 to 10−8 at the FMQ oxygen buffer. We have performed experiments at 0.5–2 GPa and 1200–1500 °C to investigate the dissolution behaviour of chlorine in silicate melts. The experiments were performed with chlorine fugacities controlled by mixtures of Ag, AgCl and AgI and oxygen fugacity buffered at C-CO-CO 2 (CCO) and Re-ReO 2. The results demonstrate that the initial chlorine dissolution mechanism involves the replacement of O2− in the silicate melt by two dissociated Cl− ions according to the reaction: Cl 2 + [O2− melt = 2[Cl− melt + 0.5O 2. The same dissolution mechanism applies to hydrous, fluid-saturated basalt at 100–200 MPa/1050 °C. Experiments using both an Fe-free haplobasaltic composition (An 50 Di 28 Fo 22) and an Icelandic basalt followed the predicted dependence of Cl concentration on f (Cl 2)0.5 and f (O 2)0.25. This Henrian behaviour extends from 0 to at least 2.6 wt% Cl dissolved in the haplobasaltic composition, 1.6 wt% Cl in anhydrous basalt and ∼1.5 wt% Cl in fluid-saturated basalt. Deviations from Henry's Law behaviour at higher concentrations are consistent with progressive association of Cl− ions. In the Henry's Law region Cl concentration in the An 50 Di 28 Fo 22 composition is given by (wt%): log Cl melt = 1.206 32 - 940 40 P T - 0.25 l o g f O 2 + 0.5 l o g f Cl 2 P is in GPa, T in kelvin, values in brackets are 1 standard error, and f (Cl 2) and f (O 2) refer to standard states of pure gas at 0.1 MPa and the temperature of interest. For the natural anhydrous basalt we obtain: log Cl melt = 0.984 64 - 930 70 P T - 0.25 l o g f O 2 + 0.5 l o g f Cl 2 By considering the P-T dependences of the Cl contents of melts we find that the concentrations observed in nature are extremely stable in basalt to very low pressures. Basalts containing the typical concentration range of 0.05–0.5 wt% Cl should, for example, only begin to degas their chlorine significantly, as HCl, at pressures in the range 0–5 MPa. Data on hydrous, fluid-saturated basalt at 100–200 MPa are, when corrected for dissolution of Ca, Na and K in the fluid, broadly consistent with our results for anhydrous basalt. Finally, we use recently evaluated thermodynamic data for sodalite (Na 4 Al 3 Si 3 O 12 Cl) to calculate the conditions under which this phase would stabilise in trachytes and phonolites. We find that the appearance of sodalite as a liquidus phase reflects a combination of low liquidus temperature and high Na 2 O activity rather than unusually high chlorine fugacity. [ABSTRACT FROM AUTHOR]

These three books consider the nature and evolutionary context of the individual and collective behavior of modern humans. Moffett's The Human Swarm and Christakis' Blueprint focus on the "big picture." What, if anything, is distinctive about the ways groups of modern humans behave? What do modern human societies have in common that distinguishes them from aggregations of non-human organisms? Wrangham's The Goodness Paradox focuses more narrowly on aggression, and the enigma that modern humans seem to be individually relatively docile, but collectively capable of planning and executing highly aggressive activities. I was intrigued and educated by all three books. [ABSTRACT FROM AUTHOR]

As part of a project to investigate the volatilities of so-called "moderately volatile elements" such as Zn, In, Tl, Ga, Ag, Sb, Pb, and Cl during planetary formation, we began by re-calculating the condensation temperatures of these elements from a solar gas at 10-4 bar. Our calculations highlighted three areas where currently available estimates of condensation temperature could be improved. One of these is the nature of mixing behavior of many important trace elements when dissolved in major condensates such as silicates, Fe-rich metals, and sulfides. Nonideal solution of the trace elements can alter (generally lower) condensation temperatures by up to 500 K. Second, recent measurements of the halogen contents of CI chondrites (Clay et al. 2017) indicate that the solar system abundance of chlorine is significantly overestimated, and this affects the stabilities of gaseous complexes of many elements of interest. Finally, we have attempted to improve on previous estimates of the free energies of chlorine-bearing solids since the temperature of chlorine condensation has an important control on the condensation temperatures of many trace elements. Our result for the 50% condensation temperature of chlorine, 472 K is nearly 500 K lower than the result of Lodders (2003), and this means that the HCl content of the solar gas at temperatures <900 K is higher than previously estimated. We based our calculations on the program PHEQ (Wood and Hashimoto 1993), which we modified to perform condensation calculations for the elements H, O, C, S, Na, Ca, Mg, Al, Si, Fe, F, Cl, P, N, Ni, and K by free energy minimization. Condensation calculations for minor elements were then performed using the output from PHEQ in conjunction with relevant thermodynamic data. We made explicit provision for nonidealities using information from phase diagrams, heat of solution measurements, partitioning data and by using the lattice strain model for FeS and ionic solids and the Miedema model for solutions in solid Fe. We computed the relative stabilities of gaseous chloride, sulfide, oxide, and hydroxide species of the trace elements of interest and used these, as appropriate in our condensation calculations. In general, our new 50% condensation temperatures are similar to or, because of the modifications noted above, lower than those of Lodders (2003). [ABSTRACT FROM AUTHOR]

The research agenda of paleoanthropology involves many topics and methodologies. Fossil specimens are allocated to species, and those species are assigned to the hominin clade. After that we want to know how they are related to each other, what they ate, how much they weighed, how smart they were, etc. We also want to know about the origin of particular attributes of hominins, such as our delayed growth and development, bipedalism, and language. The data available to answer these complex questions are confounded by fragmentary fossil specimens, small sample sizes, limited opportunities for controlled experimentation, and the inherent limitations of historical data. Also, because many traits are effectively unique to hominins, even observational comparative studies are inevitably limited in what they can tell us, if not impossible to conduct. We explore how these limitations should, but often do not, constrain the questions that paleoanthropologists should attempt to answer. [ABSTRACT FROM AUTHOR]

We have performed experiments at 1.5 GPa over the temperature range 1400–2100 °C to determine the partitioning of lithophile elements (U, Th, Eu, Sm, Nd, Zr, La, Ce, Yb) between sulfide liquid, low-S metals and silicate melt. The data demonstrate pronounced increases in partitioning of all the lithophile elements into sulfide at very low FeO contents (<1 wt%) of the silicate melt such that D U = [ U ] sulfide [ U ] silicate exceeds 1 and may be >10 in some cases. Similarly D Sm may be >2 under the same conditions of low silicate FeO. This strong partitioning behaviour is found only be important in S-rich metals, however because the observed effect of low FeO on partitioning is uniquely confined to metallic melts close to stoichiometric FeS in composition. The results and the effects of FeS content of the metal and FeO content (or activity) of the silicate may be understood in terms of exchange reactions such as: UO 2 + 2 FeS = 2 FeO + US 2 Silicate sulfide silicate sulfide High concentrations of FeS (in metal) and low FeO contents of the silicate melts drive the reaction to the right, favouring high US 2 in the sulfide and hence high D U . The effect is, we find, enhanced by the high solubility of S in the silicate (up to 11 wt%) at low FeO contents. This S content greatly reduces the activity coefficient of FeO in the silicate melt, enhancing the displacement of the reaction to the right. For sulfide-silicate partitioning at 1.5 GPa and 1400 °C we obtain D Nd /D Sm of about 1.4 and D Th ∼ 0.1D U . With increasing temperature the differences between these geochemically similar element pairs decreases such that, at 2100 °C D Nd /D Sm is 1.0 and D Th /D U is about 0.3. We used these results, together with D U and D Sm to model addition of a putative Mercury-like component (with FeS core) to early Earth. We find that the 1400° results could lead to a significant (∼11 ppm) 142 Nd anomaly in silicate Earth and add >8 ppb U to the core, but lead to an unreasonably high Th/U of silicate Earth (4.54). Based on the 2100 °C results the 142 Nd anomaly would be 0 but addition of the sulfur-rich body could add up to 10 ppb of U to the core, generating, when the accompanying 21 ppb Th is also considered, ∼3 TW of the energy required for the geodynamo. In this case, the Th/U ratio of silicate Earth would approximate 4.3, within the range of some estimates. [ABSTRACT FROM AUTHOR]

The majority of attempts to reconstruct the evolutionary history of the hominin clade proceed as if the hominin fossil record is a precise, accurate, and comprehensive record of human evolutionary history. In this contribution we review the various ways in which the apparent scarcity of early hominins on the landscape means that the existing hominin fossil record almost certainly falls short of this assumption, especially with respect to taxic diversity, as well as the spatial and temporal distribution of known taxa. We also suggest that interpretations of the hominin fossil record are particularly affected by practices that likely violate the principles of reproducibility, as well as by confirmation bias. The hominin fossil record should be seen for what it is; an incomplete record of human evolutionary history that limits what should be said about it. Generated narratives should be treated as heuristic devices, not as accurate and comprehensive descriptions of past events. [ABSTRACT FROM AUTHOR]

Physical simulations of the origin of the Moon have, until recently, centred on impact, about 100 M.yr after the origin of the solar system, of a Mars-like body (10–20% Earth mass) on a near fully-accreted protoEarth. Although this model provides an explanation of the distribution of mass and moment of inertia of the Earth–Moon system it has recently been found that modification of the initial conditions greatly expands the range of permissible impactor masses. Here we take an alternative approach and consider how the oxidation state and mass of the impactor affect the chemical compositions of the product Earth and Moon. We apply the constraints that silicate Moon is richer in FeO than silicate Earth (9–13% as opposed to 8.05%), that their Hf/W ratios are both ∼25 and that they are virtually identical in isotopes of O, Ti, Si, Ni, Cr and W. We then grow protoEarth using a standard accretionary model which yields the correct mantle abundances of Ni, Co, W, Mo, Nb, V and Cr, and add to this body different masses of impactor. The impactor is assumed to be either highly oxidised (∼18% FeO), highly reduced (∼0.3% FeO) or undifferentiated and chondritic. In order to satisfy the isotopic constraints silicate Moon is assumed to be derived principally from silicate protoEarth. We find that an oxidised or chondritic impactor of ∼ 0.15 M E can satisfy the isotopic constraints (most importantly ε 182 W), FeO contents and Nb/Ta of Earth and Moon, but leads to implausibly low Hf/W of ∼ 12 – 16 in silicate Earth and ∼ 4 – 6 in silicate Moon. This is because the Moon requires more impactor mantle, with low Hf/W, than Earth to reach its higher FeO content. In contrast, impact of a similar mass (10–20% M E ) of highly reduced, Mercury-like impactor on an oxidised protoEarth (∼10.7% FeO in mantle) satisfies the isotopic constraints, FeO contents, Nb/Ta and Hf/W of silicate Earth and Moon given a small amount of post-impact re-equilibration of terrestrial mantle with impactor core. The presence of a small S-rich lunar core is consistent with this reduced impactor scenario. We conclude that the geochemical properties of Earth and Moon strongly favour a reduced impactor of 10–20% M E . [ABSTRACT FROM AUTHOR]

ABSTRACT In this review of the evidence for and against taxic diversity within the hominin clade, we begin by looking at the logic and the history of simple 'ladder-like' interpretations of the hominin fossil record. We then look at the hominin fossil record in a series of time intervals and use current published evidence about the first and last appearance dates of each taxon to decide whether a species or specimens should be included in one, or more, of the intervals. Within each time interval, we consider the strength of the evidence that more than one hominin species is sampled. Decisions about whether taxonomic diversity exists depend on what alpha taxonomic hypotheses are used and although we use a relatively speciose interpretation of the hominin fossil record, we also explore what impact more inclusive interpretations of alpha taxonomy would have on assessments of hominin taxic diversity. With the exception of the oldest (7-5 Ma) all of the other time intervals have in our judgment at least one well-supported example of taxic diversity and several have multiple examples. In summary, not all new hominin taxa are created equally, but while taxic diversity may not be as prevalent as some have claimed, it is a feature of the hominin clade from 4 Ma until c.40 ka years ago. Am J Phys Anthropol 159:S37-S78, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Comparative genomic analysis of the nuclear receptor family suggests that the testicular receptor 2, Nr2c1 , undergoes positive selection in the human-chimpanzee clade based upon a significant increase in nonsynonymous compared to synonymous substitutions. Previous in situ analyses of Nr2c1 lacked the temporal range and spatial resolution necessary to characterize cellular expression of this gene from early to mid gestation, when many nuclear receptors are key regulators of tissue specific stem or progenitor cells. Thus, we asked whether Nr2c1 protein is associated with stem cell populations in the mid-gestation mouse embryo. Nr2c1 is robustly expressed in the developing olfactory epithelium. Its expression in the olfactory epithelium shifts from multiple progenitor classes at early stages to primarily transit amplifying cells later in olfactory epithelium development. In the early developing central nervous system, Nr2c1 is limited to the anterior telencephalon/olfactory bulb anlagen, coincident with Nestin -positive neuroepithelial stem cells. Nr2c1 is also seen in additional cranial sensory specializations including cells surrounding the mystacial vibrissae, the retinal pigment epithelium and Scarpa's ganglion. Nr2c1 was also detected in a subset of mesenchymal cells in developing teeth and cranial bones. The timing and distribution of embryonic expression suggests that Nr2c1 is primarily associated with the early genesis of mammalian cranial sensory neurons and craniofacial skeletal structures. Thus, Nr2c1 may be a candidate for mediating parallel adaptive changes in cranial neural sensory specializations such as the olfactory epithelium, retina and mystacial vibrissae and in non-neural craniofacial features including teeth. [ABSTRACT FROM AUTHOR]

We have performed an experimental and modeling study of the partial melting behavior of the HED parent body and of the fractional crystallization of liquids derived from its mantle. We estimated the mantle composition by assuming chondritic ratios of refractory lithophile elements, adjusting the Mg# and core size to match the density and moment of inertia of Vesta, and the compositions of Mg-rich olivines found in diogenites. The liquidus of a mantle with Mg# (=100*[Mg/(Mg+Fe)]) 80 is ~1625 °C and, under equilibrium conditions, the melt crystallizes olivine alone until it is joined by orthopyroxene at 1350 °C. We synthesized the melt from our 1350 °C experiment and simulated its fractional crystallization path. Orthopyroxene crystallizes until it is replaced by pigeonite at 1200 °C. Liquids become eucritic and crystal assemblages resemble diogenites below 1250 °C. MELTS correctly predicts the olivine liquidus but overestimates the orthopyroxene liquidus by ~70 °C. Predicted melt compositions are in reasonable agreement with those generated experimentally. We used MELTS to determine that the range of mantle compositions that can produce eucritic liquids and diogenitic solids in a magma ocean model is Mg# 75-80 (with chondritic ratios of refractory elements). A mantle with Mg# ~ 70 can produce eucrites and diogenites through sequential partial melting. [ABSTRACT FROM AUTHOR]

Sulfides, although modally of low abundance in most igneous rocks, have strong influences on the geochemical behavior of many elements including Pb, Cu, Ni, and the PGEs. In a recent paper, we demonstrated a simple relationship between the sulfide-silicate partition coefficients DMsulf/sil of such elements and the FeO content of the coexisting silicate melt (Kiseeva and Wood 2013). logDMsulf/sil A-n/2 log [FeO] where n is the valency of element M, [FeO] is the concentration of FeO in the silicate in wt%, and A is a constant that depends on temperature and pressure. Elements that closely obey the simple model are Pb, In, Sb, Cd, Co, Zn, and Cr. We show here, however, that the fitted slope n depends not only on the valency of element M, but also on how M interacts with oxygen, the dissolution of which as FeO in the sulfide increases as the FeO content of the silicate melt increases. To take account of interactions of trace element M with FeO dissolved in the sulfide we introduce an additional parameter ... (Wagner 1962), which represents the difference between the lithophile and chalcophile properties of M and those of Fe. If ... is positive, then element M is more chalcophile than Fe and if negative more lithophile. We performed experiments to investigate partitioning of lithophile Nb, Ta, Ce, and Ti between sulfide and simplified basaltic melt and find that they all exhibit, as expected, concave upward behavior on a plot of logD vs. log[FeO]. New experiments on Cu at low FeO contents confirm that it is more chalcophile than Fe, yielding a concave-downward curve of logD vs. log[FeO]. The combined results mean that nominally lithophile elements may partition more strongly into sulfide than nominally chalcophile elements at either very low or very high FeO contents of the silicate melt. For example, as the FeO content of the silicate melt declines below about 1 wt%, the partition coefficient of Cu, DCusulf/sil declines to an unusually low value (DCusulf/sil ~80), whereas those for Nb (DNbsulf/sil ~600), and rare earths (REE's) increase strongly. Under these conditions, Nb is, therefore, substantially more "chalcophile" than Cu in that it partitions much more strongly into sulfide. The implications of these observations for the Earth are that under a wide range of conditions one would expect significant partitioning of REE, Nb, Ta, Ti, and other lithophile elements into sulfides. Wohlers and Wood (2015) have, for example, shown that the partitioning of U and the REE into sulfides at low FeO content of the silicate is sufficiently pronounced that addition of a reduced sulfur-rich body to the accreting Earth could generate observable fractionation of Nd from Sm and, together with S, transfer sufficient U to the core to provide a significant energy source for the geodynamo. [ABSTRACT FROM AUTHOR]

We develop a comprehensive model to describe trace and minor element partitioning between sulphide liquids and anhydrous silicate liquids of approximately basaltic composition. We are able thereby to account completely for the effects of temperature and sulphide composition on the partitioning of Ag, Cd, Co, Cr, Cu, Ga, Ge, In, Mn, Ni, Pb, Sb, Ti, Tl, V and Zn. The model was developed from partitioning experiments performed in a piston-cylinder apparatus at 1.5 GPa and 1300 to 1700 °C with sulphide compositions covering the quaternary FeS NiS CuS 0.5 FeO. Partitioning of most elements is a strong function of the oxygen (or FeO) content of the sulphide. This increases linearly with the FeO content of the silicate melt and decreases with Ni content of the sulphide. As expected, lithophile elements partition more strongly into sulphide as its oxygen content increases, while chalcophile elements enter sulphide less readily with increasing oxygen. We parameterised the effects by using the ε -model of non-ideal interactions in metallic liquids. The resulting equation for partition coefficient of an element M between sulphide and silicate liquids can be expressed as log ⁡ D M sulph / sil = A + B T − n 2 log ⁡ [ FeO ] corr + 1673 T [ ε MS n / 2 FeO log ⁡ ( 1 − x FeO ) + ε MS n / 2 NiS log ⁡ ( 1 − x NiS ) + ε MS n / 2 CuS 0.5 log ⁡ ( 1 − x CuS 0.5 ) ] where A is a constant related to the entropy change of the partitioning reaction, B is a constant related to its enthalpy and n is the valency of the element of interest. Interaction parameters ε FeO , ε NiS and ε CuS 0.5 refer to non-ideal interactions between trace element and matrix, x FeO , x NiS , x CuS 0.5 and x FeS are mole fractions of FeO, NiS, and CuS 0.5 in sulphide and FeO corr is FeO content of silicate liquid (wt%) corrected for the ideal activity of FeS in the sulphide as follows: [ FeO ] corrected = [ FeO ] silicate [ Fe / ( Fe + Ni + Cu ) ] sulph We find, for most elements, that the effect of Ni and Cu on partitioning is significantly smaller than the effect of oxygen. The effects of temperature are greatest for Ni, Cu and Ag. We used our model to calculate the amount of sulphide liquid precipitated along the liquid line of descent of MORB melts and find that 70% of silicate crystallisation is accompanied by ∼0.23% of sulphide precipitation. The latter is sufficient to control the melt concentrations of chalcophile elements such as Cu, Ag and Pb. Our partition coefficients and observed chalcophile element concentrations in MORB glasses were used to estimate sulphur solubility in MORB liquids. We obtained between ∼800 ppm (for primitive MORB) and ∼2000 ppm (for evolved MORB), values in reasonable agreement with experimentally-derived models. The experimental data also enable us to reconsider Ce/Pb and Nd/Pb ratios in MORB. We find that constant Ce/Pb and Nd/Pb ratios of 25 and 20, respectively, can be achieved during fractional crystallisation of magmas generated by 10% melting of depleted mantle provided the latter contains >100 ppm S and about 650 ppm Ce, 550 ppm Nd and 27.5 ppb Pb. Finally, we investigated the hypothesis that the pattern of chalcophile element abundances in the mantle was established by segregation of a late sulphide matte. Taking the elements Cu, Ag, Pb and Zn as examples we find that the Pb/Zn and Cu/Ag ratios of the mantle can, in principle, be explained by segregation of ∼0.4% sulphide matte to the core. [ABSTRACT FROM AUTHOR]

Closely related species are likely to experience resource competition in areas where their ranges overlap. Fossil evidence suggests that hominins in East Africa c. 2-1.5 million years ago may have lived synchronically and sympatrically, and that competition may have contributed to the different tooth sizes observed in Homo and Paranthropus. To assess the likelihood that these taxa overlapped, we applied a character displacement model to the postcanine tooth size of fossil hominins and validated this model in populations of living primates. Mandibular fourth premolar (P4) crown size was measured from fossil taxa and from living primate species where dietary overlap is established. Dimensions of the P4 crown were fitted to a character matrix and described as the response variables of a generalized linear model that took taxon and location as input variables. The model recovered significant divergence in samples of closely related, living primates. When applied to fossil hominins the same model detected strong indications of character displacement between early Homo and Paranthropus ( P = 0.002) on the basis of their P4 crown size. Our study is an example of how ecologically informed morphologies measured in appropriate extant referents can provide a comparative context for assessing community and ecological evolution in the fossil record. [ABSTRACT FROM AUTHOR]

Recent 142Nd 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 or to loss of an early-formed terrestrial crust by impact ablation. 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. 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. 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 142Nd/144Nd 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. [ABSTRACT FROM AUTHOR]

The inhibitory cascade is a mathematical model for interpreting the relative size of the occlusal surfaces of mammalian molars in terms of developmental mechanisms. The cascade is derived from experimental studies of mouse molars developed in culture, and has been tested and applied to the dentitions of rodents, ungulates, carnivores, and platyrrhines. Results from such applications have provided new information regarding the origins of plesiomorphic traits in mammalian clade and how derived morphologies may arise. In this study we apply the inhibitory cascade model to the postcanine dentition of a sample of Old World primates that includes fossil hominins. The results of this study suggest that the inhibitory cascade (i.e. M1 < M2 < M3) describes the relative sizes of the molar occlusal areas of Old World primates and is likely the plesiomorphic condition for this clade. Within that clade, whereas most Old World monkeys have a M1 < M2 < M3 pattern, most apes have a M1 < M2 ≈ M3 pattern. This modified cascade suggests that greater levels of inhibition (or less activation) are acting on the posterior molars of apes, thus facilitating the reduction of M3s within the apes. With the exception of the baboon genus Papio, extant congeners typically share the same molar inhibitory cascade. The differences in the relative size relationships observed in the molar and premolar-molar cascades of the species included in the fossil hominin genus Paranthropus suggest that although large postcanine teeth are a shared derived trait within this genus, the developmental basis for postcanine megadontia may not be the same in these two Paranthropus taxa. Our results show that phenotypic characters such as postcanine megadontia may not reflect common development. [ABSTRACT FROM AUTHOR]

The accretion of the Earth was marked by the high-pressure segregation of the core, accompanied by dissolution of about 10% of one or more “light” elements into the metal. Cosmochemical data suggest that, of these 10% “light” elements, the core contains ∼1.7% S (Dreibus and Palme, 1996) and there is evidence that volatile elements such as S accreted to the Earth late in planetary growth, plausibly as a sulfide “matte” (O’Neill, 1991). Given that metallurgical data indicate that dissolution of even small amounts of sulfur in liquid Fe can have profound effects on the activities of some trace components, we have undertaken a study of the affect of S on the metal–silicate partitioning of a number of the most important chalcophile and siderophile elements. We performed experiments at 1.5 GPa and 1460–1650 °C on metal–silicate partitioning of W, Mo, Ni, Co, Cu, Ag, Mn, Cd, Tl, Cr, Sb, In, Pb, Ga, Ge, V and Zn under conditions where the S content of the metal was varied from 0 to 37 wt%. Mn and Ag were found to exhibit the highest ratio of chalcophile to siderophile behaviour while W, Ga and Sb are the most “chalcophobic” of the elements studied. In terms of the 1-parameter epsilon model (Wagner, 1962) we derived values for each element at 1600 °C as follows (negative values indicate chalcophile behaviour): ε Cu S = - 2.57 ; ε Mn S = - 6.41 ; ε Ag S = - 4.15 ; ε Sb S = 4.36 ; ε Cd S = - 3.78 ; ε In S = - 0.24 ; ε Tl S = - 6.21 ; ε Ga S = 6.54 ; ε Pb S = - 3.73 ; ε Cr S = - 3.70 ; ε Ge S = 7.03 ; ε V S = - 3.14 ; ε Zn S = - 1.68 ; ε Mo S = 2.27 ; ε W S = 6.47 ; ε Ni S = 2.17 ; ε Co S = 2.40 . We use these new data in conjunction with published pressure–temperature dependences of metal–silicate partitioning to test the effects of accreted S on the calculated trace element concentrations in bulk silicate Earth. The approach employs a continuous accretion model in which the oxidation state of the Earth and pressure of core segregation both increase during accretion. We find that, without addition of S in the latter stages of accretion, the Mo/W ratio of silicate Earth would be several times larger than that observed. Addition of ∼2% S accompanied by small amounts of carbon in the last 15% of accretion, however, enables us to match the observed concentrations of these elements in silicate Earth. This confirms an earlier conclusion that the Mo/W ratio of silicate Earth requires late sulfide addition to the core (Wade et al., 2012). Further support for late sulfide addition to the core comes from the depletion factors of volatile chalcophile elements Cu, Ga, Sb, Ag, Zn, Pb, Cd, In and Tl in silicate Earth relative to lithophile elements of similar volatility. We find that depletions of these elements are well correlated with their partition coefficients into sulfide (FeS) liquids at 1.5 GPa and temperatures of 1460–1650 °C. In contrast there is essentially no correlation between their depletion factors and sulfur-free liquid Fe–silicate partition coefficients. [ABSTRACT FROM AUTHOR]

Abstract: We have determined the partitioning of the elements Cu, In, Tl, Pb, Ag, Mn, Zn, Cr, Co, Ni, Sb and Cd between FeS-rich sulphide liquids and anhydrous basaltic melts at high pressures and temperatures. The sulphide liquids were found to have oxygen contents which are linearly related to the FeO contents of the silicate melts. We also found simple relationships between the FeO contents of the silicate melts and the sulphide–silicate partition coefficients for the individual trace elements. These relationships can be generally represented as follows: where A is a constant related to the free energy of Fe–M exchange, n is a constant related to the valence of the element and [FeO] is the FeO content of the silicate melt in mole fraction or weight %. This simple relationship effectively removes the need to define the fugacity ratio when considering partitioning and hence greatly simplifies application of partitioning data to natural systems. In theory n should approximate −1 for 1+ ions, −2 for 2+ ions and so on. Regressed values of n are generally close to those expected, although deviations occur for some elements. The deviations can be understood in terms of the relative chalcophile and lithophile characteristics of the element of concern. For cases in which the sulphide is an FeS–NiS–Cu2S liquid we obtain excellent agreement with results for pure FeS by correcting the FeO content of the silicate melt as follows: We tested our model on data from the literature in which sulphide–silicate partition coefficients for Cu, Co, Ni and Mn were determined. Literature data for these elements follow the predicted linear dependence of on . Furthermore, differences between the absolute values of obtained by us and those in the literature are quantifiable in terms of temperature and matrix effects such as the Ni/Fe ratio of the sulphide. We used our results for Pb partitioning to calculate Ce/Pb and Nd/Pb ratios of basalts generated by partial melting of the mantle followed by fractional crystallization. Calculated Nd/Pb is essentially constant over wide ranges of partial melting and fractional crystallization with a value of ∼18.6 if we assume that depleted mantle contains 65 ppb of Pb. Calculated Ce/Pb varies slightly during batch partial melting from 21 to 29 with the canonical value of 25 being achieved at partial melting. These trends are in excellent agreement with measurements of oceanic basalt glasses. Finally, we used our partitioning relationships to calculate the concentrations of a number of the incompatible chalcophile trace elements in depleted mantle. These are as follows: 32 ppm Cu, 65 ppb Pb, 7.6 ppb Ag, 12 ppb In, 23 ppb Cd, 1.7 ppb Sb and 1.3 ppb Tl. [Copyright &y& Elsevier]

The present publication reviews the broader evolutionary implications of our long-term study of primate musculature. It summarizes the implications of the study for our understanding of the use of myological characters for phylogenetic reconstruction, for assessing the importance of homoplasy and reversions in evolution, and for our understanding of Dollo's law, the notion of 'direction' in evolution, the common myth of human complexity, the tempo and mode of primate and human evolutionary history, adaptive radiations, the notion that 'common' equals 'primitive' and the influence of morphogenesis on the variability of head, neck, pectoral and upper limb muscles. Among other results our study shows that myological characters are useful for phylogenetic reconstruction. The results also stress the importance of homoplasy and of evolutionary reversions in morphological evolution, and they provide examples of reversions that violate Dollo's law due to the retention of ancestral developmental pathways. They also show that contrary to the idea of a 'general molecular slow-down of hominoids' the rates of muscle evolution at the nodes leading to and within the hominoid clade are higher than those in most other primate clades. However, there is no evidence of a general trend or 'directionality' towards an increasing complexity during the evolutionary history of hominoids and of modern humans in particular, at least regarding the number of muscles or of muscle bundles. The rates of muscle evolution at the major euarchontan and primate nodes are different, but within each major primate clade ( Strepsirrhini, Platyrrhini, Cercopithecidae and Hominoidea) the rates at the various nodes, and particularly at the nodes leading to the higher groups (i.e. those including more than one genus) are strikingly similar. Our results also support, in general terms, the assumption that 'common is primitive' and they lend some support for the 'vertebrate-specific model' in the sense that during the divergent events that resulted in these four major primate clades there was more emphasis on postcranial changes than on cranial changes. Our study of primates does not, however, support suggestions that the distal structures of the upper limb are more prone to variation than the proximal ones, or that the topological origins of the upper limb muscles are more prone to evolutionary change than their insertions. [ABSTRACT FROM AUTHOR]

Enamel has long been of interest for its functional and phylogenetic significance among fossil hominins and other primates. Previous studies demonstrated that enamel incremental features distinguish among hominin fossil taxa, suggesting utility for highlighting taxonomy. However, not all features appear to be useful in mixed samples of fossils, living humans, and apes. Here we tested enamel incremental data from closely related primate taxa to determine which features, if any, distinguish among them. Enamel incremental variables were measured from the M 2 of 40 living primate taxa, and we tested our variables using discriminant function analysis at the taxonomic ranks of parvorder, family, tribe, and genus. We then included enamel incremental data from Australopithecus afarensis , Australopithecus africanus , Paranthropus aethiopicus , Paranthropus boisei , and Paranthropus robustus to determine if these features distinguished fossil taxa from living humans and apes. Our initial results show that enamel incremental variables distinguish among primate taxa, but with low classification rates. Further testing with jackknifing methods shows overlap between groups at all taxonomic ranks, suggesting enamel incremental variables are unreliable for taxonomy. The addition of many common enamel incremental growth variables also resulted in multicollinearity in our multivariate analysis. As the dentition and isolated teeth remain a significant portion of the hominin fossil record, verifying enamel incremental features as a useful taxonomic tool is fundamentally important for hominin paleobiology. [ABSTRACT FROM AUTHOR]

Abstract: Questions of alpha taxonomy are best addressed by comparing unknown specimens to samples of the taxa to which they might belong. However, analysis of the hominin fossil record is riddled with methods that claim to evaluate whether pairs of individual fossils belong to the same species. Two such methods, log se m and the related STET method, have been introduced and used in studies of fossil hominins. Both methods attempt to quantify morphological dissimilarity for a pair of fossils and then evaluate a null hypothesis of conspecificity using the assumption that pairs of fossils that fall beneath a predefined dissimilarity threshold are likely to belong to the same species, whereas pairs of fossils above that threshold are likely to belong to different species. In this contribution, we address (1) whether these particular methods do what they claim to do, and (2) whether such approaches can ever reliably address the question of conspecificity. We show that log se m and STET do not reliably measure deviations from shape similarity, and that values of these measures for any pair of fossils are highly dependent upon the number of variables compared. To address these issues we develop a measure of shape dissimilarity, the Standard Deviation of Logged Ratios (s LR). We suggest that while pairwise dissimilarity metrics that accurately measure deviations from isometry (e.g., s LR) may be useful for addressing some questions that relate to morphological variation, no pairwise method can reliably answer the question of whether two fossils are conspecific. [Copyright &y& Elsevier]

Four-field anthropology departments are no longer in a 'steady state'. Their integrity is threatened by a combination of internal and external developments. It remains to be seen whether they, in combination, are powerful enough to break the historic bonds that have united them for nearly a century. [ABSTRACT FROM AUTHOR]

Abstract: Although at 1atm pressure the oxidation state of W in silicate melts is 6+at oxygen fugacities from air down to several logfO2 units below Fe-FeO (IW) equilibrium, Cottrell et al. (2009) suggested that, at pressures above 6GPa, W becomes predominantly 4+in this oxygen fugacity range. Wade and Wood (2005), using a similar, but expanded metal-silicate partitioning dataset found, however, no evidence for an oxidation state change. In order to resolve the issue we collected tungsten L3 edge XANES spectra of a series of synthetic tungsten- bearing glass standards and of silicates from a range of high-pressure (1.5 to 25GPa) metal/silicate partitioning experiments. Glass standards were made at 1atm pressure and equilibrated at oxygen fugacities spanning a range from approximately 5.5 log units below the Fe-FeO buffer (IW-5.5) to Air. Metal-silicate partitioning experiments were performed at oxygen fugacities between IW-6.2 and IW-1 and at pressures between 1.5 and 25GPa. At low pressures and oxygen fugacities above IW-3.5, W exists in the silicate melt almost exclusively as W6+ (identical L3-edge energy to WO3) with the progressive reduction to W4+ completed by about IW-6. The XANES spectra of W from experiments at 6, 7 and 25GPa are completely consistent with those from 1atm and 1.5GPa experiments and with that of WO3. We conclude that there is no change of oxidation state with increasing pressure to 25GPa and that modelling of the oxygen-fugacity dependence of core formation requires use of a+6 oxidation state of W. [Copyright &y& Elsevier]

According to Dollo's law, once a complex structure is lost it is unlikely to be reacquired. In this article, we report new data obtained from our myology-based cladistic analyses of primate phylogeny, which provide evidence of anatomical reversions violating Dollo's law: of the 220 character state changes unambiguously optimized in the most parsimonious primate tree, 28 (13%) are evolutionary reversions, and of these 28 reversions six (21%) occurred in the nodes that lead to the origin of modern humans; nine (32%) violate Dollo's law. In some of these nine cases, the structures that were lost in adults of the last common ancestor and are absent in adults of most subgroups of a clade are actually present in early ontogenetic stages of karyotypically normal individuals as well as in later ontogenetic stages of karyotypically abnormal members of those subgroups. Violations of Dollo's law may thus result from the maintenance of ancestral developmental pathways during long periods of trait absence preceding the reacquisition of the trait through paedomorphic events. For instance, the presence of contrahentes and intermetacarpales in adult chimpanzees is likely due to a prolonged/delayed development of the hand musculature, that is, in this case chimpanzees are more neotenic than modern humans. [ABSTRACT FROM AUTHOR]

Modern humans represent the only surviving species of an otherwise extinct clade of primates, the hominins. As the closest living relatives to extinct hominins, extant primates are an important source of comparative information for the reconstruction of the diets of extinct hominins. Methods such as comparative and functional morphology, finite element analysis, dental wear, dental topographic analysis, and stable isotope biogeochemistry must be validated and tested within extant populations before they can be applied to extinct taxa. Here we review how these methods have and might be used to reconstruct the diet of a particular extinct hominin, Paranthropus boisei, which has no extant analogue for its highly derived masticatory morphology. Our review emphasizes the potential and limitations of using extant primates as models for the reconstruction of extinct hominin diets. We encourage paleoanthropologists and those who study the feeding behaviors of extant primates to work together to investigate and validate methods for interpreting the diets of all extinct primates, including hominins. [ABSTRACT FROM AUTHOR]

Abstract: In order to place better constraints on the conditions of core formation on Earth and other planetary bodies we have performed experiments to determine the partitioning of Mo and W between liquid Fe-rich metal and liquid silicate at pressures of 1.5–24GPa and temperatures of 1803–2723K. Experiments performed in MgO capsules at 1.5GPa/1923K indicate that Mo is in the +4 oxidation state in the silicate at oxygen fugacities >2log units below the IW (Fe–FeO) buffer. In contrast W6+ is the dominant tungsten oxidation state in the silicate at 1.5GPa/1923K and 1.8–3.3log units below the IW buffer. When our 15 data for pressures between 6 and 24GPa are combined with those of we find evidence neither for a change in oxidation state of W above 6GPa nor for a change in pressure dependence of partitioning in the experimental fO2 range. Metal–silicate partitioning of both Mo and W shows strong dependence on silicate melt composition with both elements becoming more siderophile as the melt becomes more SiO2-rich. Although the trends in the partitioning data can be related to silicate melt composition in terms of the ratio of nonbridging oxygens to tetrahedral cations we find that use of a regular solution model for the silicate melt results in a significantly better fit to the data. We combined our results with those in the literature to obtain partitioning equations applicable to the Earth. In terms of weight partitioning we define and as follows: The experimental data, when corrected for compositional effects, yield the following expressions for a pyrolite mantle: The value in brackets corresponds to 1 standard error of the fit. These expressions were combined with the continuous accretion model of to investigate the constraints which they place on the accretionary process. We find, however, that, for accretionary paths consistent with the silicate Earth contents of Ni, Co, V, Cr and Nb, W should partition twice as strongly into the core as Mo. This is in stark contrast to the estimated core–mantle partition coefficients of ∼40 for W and 90–140 for Mo. Neither changes to the accretionary path nor the assumption of partial disequilibrium can readily alter this result. The answer appears to reside with the identity of one of the light elements in the core. We investigated the effect of S on our accretionary model by adding 2% of this element (consistent with cosmochemical estimates) to the core. If S is added at constant S/Fe ratio throughout accretion the net effect is negligible. If, however, S is added exclusively during the last 10–20% of accretion D Mo and D W become consistent with the silicate Earth contents of these elements. Only small additional adjustments to the model are required to accommodate changes in partitioning of Ni, Co, V, Cr and Nb. We conclude that the Mo and W contents of the silicate Earth indicate that S (and other moderately volatile elements) was added to the Earth during core formation but only during the last ∼20% of accretion. This conclusion is the same as that reached by from the Ag isotopic composition of silicate Earth. [Copyright &y& Elsevier]

Abstract: The Earth''s mantle is currently oxidised and out of chemical equilibrium with the core. The reasons for this and for the relatively oxidised state of Earth''s mantle relative to the mantles of other terrestrial planets are unclear. It has been proposed that the oxidised nature and high ferric iron (Fe3+) content of Earth''s mantle was produced internally by disproportionation of ferrous iron (Fe2+) into Fe3+ and metallic iron by perovskite crystallisation during accretion. Here we show that there is substantial Fe isotope fractionation between experimentally equilibrated metal and Fe3+-bearing perovskite (≥0.45‰/amu), which can account for the heavy Fe isotope compositions of terrestrial basalts relative to equivalent samples derived from Mars and Vesta as the latter bodies are too small to stabilise significant perovskite. Mass balance calculations indicate that all of the mantle''s Fe3+ could readily have been generated from a single disproportionation event, consistent with dissolution of perovskite in the lower mantle during a process such as the Moon-forming giant impact. The similar Fe isotope compositions of primitive terrestrial and low-titanium lunar basalts is consistent with models of equilibration between the mantles of the Earth and Moon in the aftermath of the giant impact and suggests that the heavy Fe isotope composition of the Earth''s mantle was established prior to, or during the giant impact. The oxidation state and ferric iron content of the Earth''s mantle was therefore plausibly set by the end of accretion, and may be decoupled from later volatile additions and the rise of oxygen in the Earth''s atmosphere at 2.45Ga. [Copyright &y& Elsevier]

Abstract: We have performed simulations of the electron microbeam analysis of metal–silicate partitioning experiments in which a small (∼50μm) ball of metal is embedded in a silicate matrix. This geometry approximates that found in many high pressure diamond-cell experiments aimed at determining the partition coefficients (D i) of elements between metal and silicate. The simulations involved using the (publicly available) Monte Carlo simulation package PENEPMA which is based on the general-purpose electron–photon transport code PENELOPE. The code allows complex geometrical structures to be defined by quadric surfaces, which enclose homogeneous materials specified by the user. The package simulates both electron and photon transport, keeps track of the X-ray production mechanism and includes the continuum contribution. Our principal results came from simulating the effects of secondary fluorescence on the apparent metal–silicate partition coefficient of Ni for the case of an Ni-rich metal (26.8% Ni, 73.2% Fe) embedded in a silicate matrix. If, as is frequently the case, analysis of the silicate is performed 5–10μm from the silicate–metal interface then secondary fluorescence of Ni in the metal will increase the apparent NiO concentration in the silicate by ∼1000ppm. In the case considered, this is 25% of the Ni content of the silicate and the fluorescence effect decreases the apparent D Ni from 110 to 84. For this type of experiment, therefore, the fluorescence effect reduces the apparent partition coefficient. We performed similar simulations of the analysis of the centre of a 10μm diameter metal ball embedded in the silicate matrix to determine apparent Si and O concentrations in the metal. In this case, because the electrons do not penetrate so far into the metal, the fluorescence effect is very small and can be neglected. Finally, we show that focused ion beam (FIB) sections, while providing the potential physically to separate metal from silicate present additional, but not insurmountable, problems of standardisation. The best results would be obtained with a section >3μm in thickness. We recommend that, in general, experimentalists consider simulating analysis of a typical experimental product before publication of results which may be affected by secondary fluorescence. [Copyright &y& Elsevier]

We review the fossil and genetic evidence that relate to evolution in the genus Homo. We focus on the origin of Homo and on the evidence for taxonomic diversity at the beginning of the evolutionary history of Homo and in the last 200,000 years. We set out the arguments for recognizing a second early Homo taxon, Homo rudolfensis, and the arguments for and against including Homo habilis sensu stricto and Homo rudolfensis within Homo. We end by reviewing recent genomic evolution within Homo. The challenge of the upcoming decades is to meld innovations in molecular genetic methods and technology with evidence from the fossil record to generate hypotheses about the developmental bases of the phenotypic and behavioral developments we see within the genus Homo. [ABSTRACT FROM AUTHOR]

The article reports on our solar system and the origin of Earth and its moon. Topics discussed include the chemical composition of the Earth and solar system, theories about the formation of the Earth and Moon, and radioactive isotopes which are used to date rocks and meteorites. Also reported are unanswered questions about our solar system such as the age of the moon.

We present experimental data on the partitioning of Li, Be, B, K, Mg, Sr, Ga, Rb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U, Hf, Zr, Nb and Ta between lawsonite and fluid, and zoisite and fluid at 3·0–3·5 GPa and 650–850°C. The aim is to provide data bearing on the trace element contents of fluids released during dehydration of subducting oceanic crust. Experimental trace element partition coefficients for lawsonite indicate a preference for the light rare earth elements (LREE) over the heavy REE (HREE) and for Be. These characteristics are consistent with the chemical composition of lawsonite in natural rocks. Experimental trace element partition coefficients for zoisite indicate a preference for HREE relative to LREE. This observation, consistent with earlier experimental data, is the reverse of the observed trace element compositions of natural zoisites, indicating the influence of other factors on the trace element contents of this phase. Lattice strain theory explains well the experimentally derived partitioning of divalent cations in the Ca-site between lawsonite and fluid. However, the weak relative fractionation of REE between lawsonite and fluid cannot be explained by lattice strain theory, as previously observed for zoisite–fluid REE partitioning. We combine our experimental data with thermodynamic models of mineral stability to model the compositions of fluids released during subduction of altered normal mid-ocean ridge basalt. The low La/Sm ratio associated with very high Ba/Th in arc magmas can be explained only if allanite is stable in the subducting oceanic crust. This suggests that the crustal fluid component involved in arc magma petrogenesis results from processes occurring in the warm, top part of the subducting slab. Decreasing lawsonite modal proportion with depth is associated with a large release of fluid characterized by low B/Be ratios that could explain the decreasing B/Be ratios in arc magmas with increasing distance from the trench. This implies that an important Be input in arc magma originates from the fluid generated during oceanic crust dehydration. [ABSTRACT FROM AUTHOR]