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The relationships among the living apes and modern humans have effectively been resolved, but it is much more difficult to locate fossil apes on the tree of life because shared [...]

The meaning of the age of the Earth defined by lead isotopes has long been unclear. Recently it has been proposed (1) that the age of the Earth deduced from [...]

Previous research has demonstrated that species and subspecies of extant chimpanzees and bonobos can be distinguished on the basis of the shape of their molar crowns. Thus, there is potential for fossil taxa, particularly fossil hominins, to be distinguished at similar taxonomic levels using molar crown morphology. Unfortunately, due to occlusal attrition, the original crown morphology is often absent in fossil teeth, and this has limited the amount of shape information used to discriminate hominin molars. The enamel--dentine junction (EDJ) of molar teeth preserves considerable shape information, particularly in regard to the original shape of the crown, and remains present through the early stages of attrition. In this study, we investigate whether the shape of the EDJ of lower first and second molars can distinguish species and subspecies of extant Pan. Micro-computed tomography was employed to non-destructively image the EDJ, and geometric morphometnc analytical methods were used to compare EDJ shape among samples of Pan paniscus (N = 17), Pan troglodytes troglodytes (N = 13), and Pan troglodytes verus (N = 18). Discriminant analysis indicates that EDJ morphology distinguishes among extant Pan species and subspecies with a high degree of reliability. The morphological differences in EDJ shape among the taxa are subtle and relate to the relative height and position of the dentine horns, the height of the dentine crown, and the shape of the crown base, but their existence supports the inclusion of EDJ shape (particularly those aspects of shape in the vertical dimension) in the systematic analysis of fossil hominin lower molars. KEY WORDS tooth morphology; micro-computed tomography; geometric morphometrics; sliding semilandmarks

In Figure 6, we compare Mg#s (where Mg# = Mg/[Fe SP 2+ sp +Mg], atomic) of bulk olivine-phyric shergottites to the most Mg-rich olivine phenocrysts. Keywords: Olivine-phyric shergottites; Fe2+-Mg partitioning; olivine; basalt; Mars EN Olivine-phyric shergottites Fe2+-Mg partitioning olivine basalt Mars 1442 1452 11 07/05/22 20220701 NES 220701 Introduction The partitioning of elements between solid and liquid phases is an important tool for understanding and modeling igneous processes. Measuring Fe SP 3+ sp /Fe SP 2+ sp in silicate liquids is difficult; as a result, Fe SP 3+ sp /Fe SP 2+ sp of a melt it is often assumed to be negligible (e.g., [27]) or calculated using prior experimental calibrations (e.g., [79]; [52]). To ensure olivine saturation at the liquidus, we added ~17% synthetic olivine (enough to ensure olivine saturation but still dominated by liquid to facilitate rapid equilibration) with an Mg# of 77 (the estimated Mg# of olivine in the primitive martian mantle; [27]). [Extracted from the article]

The principles of fracture and deformation of solids from the engineering material science are applied to determine the correlation between the differences in shape, size, structure and properties of the enamel cap covering mammalian teeth and the dietary behavior of mammals.

Paranthropus boisei is a hominin taxon with a distinctive cranial and dental morphology. Its hypodigm has been recovered from sites with good stratigraphic and chronological control, and for some morphological regions, such as the mandible and the mandibular dentition, the samples are not only, relatively well dated, but they are, by paleontological standards, reasonably-sized. This means that researchers can trace the evolution of metric and nonmetric variables across hundreds of thousands of years. This paper is a detailed review of half a century's worth of fossil evidence and analysis of P. boisei and traces how both its evolutionary history and our understanding of its evolutionary history have evolved during the past 50 years. KEY WORDS Paranthropus; boisei; aethiopicus; human evolution; Africa DOI 10.1002/ajpa.20732

Author(s): Bernard J. Wood (corresponding author) [1]; Michael J. Walter [2]; Jonathan Wade [2] From observations of newly formed stars it appears that the Sun's planetary system formed from a [...]

Author(s): Bernard J. Wood (corresponding author) [1, 3]; Alex N. Halliday [2] Kelvin calculated the age of the Earth to be about 24 million years by assuming conductive cooling from [...]

Author(s): Guillaume Caro (corresponding author) [1]; Bernard Bourdon [1]; Bernard J. Wood [2]; Alexandre Corgne [3] Calculations of the energetics of terrestrial accretion indicate that the Earth was extensively molten [...]

We have determined the partition coefficients of a large number of trace elements between CaTi[O.sub.3] perovskite and anhydrous silicate melts at atmospheric pressure and 3 GPa. Determination of the concentration limits of Henry's law behaviour in the CaO-[Al.sub.2][O.sub.3]-Si[O.sub.2]-Ti[O.sub.2] system reveals that the incorporation of rare earth elements (REE) and tetravalent large ion lithophile elements (LIL[E.sup.4+] such as U and Th) at the Ca-site of CaTi[O.sub.3] perovskite occurs with charge compensation through Ca-vacancy formation rather than by coupled substitution of AI for Ti. When melt composition is varied, we find that partition coefficients for REE and Th are strong functions of the CaO content of the melt. The observed trends are in excellent agreement with those predicted from the Ca-vacancy model. Given that they adopt the same crystal structure and have similar trace element partitioning behaviour, CaTi[O.sub.3] perovskite and the deep mantle phase CaSi[O.sub.3] perovskite can be considered analogous to one another. When the analogy is pursued in detail, we find that partitioning into both phases follows the composition-dependence predicted by the Ca-vacancy model. Thus, substitution of REE, [U.sup.4+] and Th into CaSi[O.sub.3] in the lower mantle also occurs with Ca-vacancy formation to balance charge. Furthermore when 2+, 3+ and 4+ partition coefficients for both phases are plotted as functions of CaO melt content, the trends for CaSi[O.sub.3] and CaTi[O.sub.3] appear to be continuous. This surprising result means that partitioning into Ca-perovskite is independent of pressure and temperature and also of whether or not the host is CaSi[O.sub.3] or CaTi[O.sub.3]. One implication is that CaSi[O.sub.3] crystallising from a peridotitic magma ocean may have partition coefficients for Th and U up to about 400. Crystallisation and sequestration of as little as 0.25 volume% of this phase in the lower mantle early in earth history would make a significant contribution to current mantle heat production.

Magmas erupted at convergent margins consist of components from both mantle wedge and subducted slab. In an effort to quantify the relative contributions of these sources, we have determined 19 trace element partition coefficients (D values) for orthopyroxene and clinopyroxene, in equilibrium with spinel and hydrous high-MgO melt under conditions appropriate to melting in the mantle wedge, i.e., 1.3 GPa, 1245 [degrees]C, and [f.sub.O2] of NNO + 1. All trace elements are more incompatible in clinopyroxene during hydrous melting than during anhydrous melting of fertile and depleted peridotite. Orthopyroxene D values are relatively insensitive to pressure, temperature, and phase composition. The new D values are used to calculate the trace-element composition of the mantle wedge, which produced primitive South Sandwich Islands and St. Vincent (Lesser Antilles) arc basalts. Both sources correspond to previously depleted mantle that has been enriched in LILEs and LREEs by slab-derived fluids. In the case of the South Sandwich Islands, the calculated source is in very close agreement with dredged fore-arc lherzolites. Our partitioning data confirm that hydrous melting of wedge peridotite itself cannot produce the characteristic enrichments of LILEs over REEs and HFSEs. Our estimates of the slab component in South Sandwich Islands and St. Vincent are consistent with estimates from other arcs, derived by alternative methods.

The age of the earliest recovered fossil evidence of a hominin taxon is all too often equated with that taxon's origination. However, the earliest known fossil record nearly always postdates, sometimes by a substantial period of time, the true origination of a taxon. Here we evaluate the first appearance records of the earliest potential hominins (Sahelanthropus, Ardipithecus, Orrorin), as well as of the genera Australopithecus, Homo, and Paranthropus, to illustrate the considerable uncertainty regarding the actual timing of origin of these taxa. By placing confidence intervals on the first appearance records of early hominin taxa, we can better evaluate patterns of hominin diversity, turnover, and potential correlations with climatic and environmental changes. [ABSTRACT FROM AUTHOR]

We have developed a predictive model for the partitioning of magnesium and a range of trivalent trace elements (rare earth elements, Y, In and Sc) between garnet and anhydrous silicate melt as a function of pressure, temperature and bulk composition. The model for the magnesium partition coefficient, [D.sub.Mg], is based on a thermodynamic description of the pyrope ([Mg.sub.3][Al.sub.2-] [Si.sub.3][O.sub.12]) melting reaction between garnet and melt. Simple activity-composition relations, which take explicit account of garnet non-ideality, link [D.sub.Mg] to the free energy of fusion ([DELTA][G.sub.[Florin]]) of pure pyrope without the need to invoke non-ideality in the liquid phase. The resulting predictive equation, based on the compositions of a large set (n = 160) of published garnet-melt pairs, produces values of [D.sub.Mg] that are within 20% of measured values at temperatures between 1,450 and 1,930 [degrees] C, and pressures between 2.5 and 7.5 GPa. The model for trivalent (3+) trace elements is based on the lattice strain approach to partitioning, which describes mineral-melt partition coefficients in terms of three parameters: the effective radius, [r.sub.0](3+), of the site on which partitioning takes place (in this case, the garnet X-site); the apparent site Young's modulus [E.sub.X](3+); and the partition coefficient [D.sub.0](3+) for a fictive trivalent element [J.sup.3+], with radius [r.sub.0](3+), that does not strain the crystal lattice when entering the garnet X-site. Analogous to the model for [D.sub.Mg], simple activity-composition relations link [D.sub.0](3+) to [DELTA][G.sub.[Florin]] of a hypothetical garnet component incorporating a hypothetical rare earth element [J.sup.3+] through a YAG-type charge-balancing mechanism ([J.sup.3+][Mg.sub.2][Al.sub.3][Si.sub.2][O.sub.12]). Through analysis of existing garnet-melt rare earth element partitioning data (n = 18 garnet-melt pairs), an expression is derived relating [D.sub.0](3+) to pressure, temperature and [D.sub.Mg]. Predicted [D.sub.REE/Y/Sc] values agree to within 5-50% of experimental measurements for all elements except La and Ce, which are liable to large experimental errors, spanning pressures between 2.5 and 5.0 GPa and temperatures between 1,430 and 1,640 [degrees] C. In conjunction with our new parameterisation for [D.sub.Mg], and previously published equations linking [r.sub.0](3+) and [E.sub.X](3+) to garnet major element composition, this model gives a description of trivalent REE, Y, In and Sc partitioning between garnets and anhydrous melts over a range of pressures, temperatures and compositions relevant to melting of garnet-bearing sources in the Earth's upper mantle.