Search

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 [...]

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 [...]

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 [...]

Bernard Wood explores a claim that our nearest cousins were our cognitive equals -- and that birds had a part to play in that.Bernard Wood explores a claim that our nearest cousins were our cognitive equals -- and that birds had a part to play in that., Author(s): Bernard WoodAuthor Affiliations:Trail of feathers to the Neanderthal mind The Neanderthal woman nicknamed Nana, reconstructed at the Gibraltar Museum, with feathers. [see PDF for image]Credit: S. Finlayson/Gibraltar National MuseumForensic [...]

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 [...]

Author(s): George R. Helffrich (corresponding author) [1, 2]; Bernard J. Wood [2] The Earth's mantle comprises 82% of its volume and 65% of its mass. It constitutes virtually all of [...]

Observation of the vestibular system of living primates and early hominids reveals that the bony labyrinth morphology explains the locomotor property and phylogenetic relationships of early hominids. The fossil hominids of Homo erectus explain the modern human semicircular canal morphology, which suggests its obligatory bipedal behavior. Australopithecus africanus exhibits a locomotor behavior of facultative bipedalism and arboreal climbing.

A study of the partitioning between silicate crystals and their melts in 15 elements showed that partition coefficients can be predicted using the quantitative relationship between elasticity of the crystal lattice and its element partitioning characteristics. A model based on the size and elastic nature of the crystal was able to explain element partitioning behavior based on the physical aspects of the cation sites. The cation site also influenced the elasticity of the crystal while the linear function of cation charge made the partitioning properties similar to these of ionic crystals.

Chewing is much like using a pestle and mortar, but upside down. Your jaw muscles supply the power and move your lower teeth (the pestle) up and across your upper [...]

The anatomy of three new fossils, including a face, lends support to the hypothesis that there were at least two parallel lineages early in the evolutionary history of our own [...]

The conventional wisdom of evolution has been challenged by O'Connell and colleagues, by suggesting that changes that led to the evolution of modern humans were initiated by systematic exploitation of subterranean food sources, and the recruitment of grandmothers. This comes from observations made in a study of the Hadza population living around Lake Eyasi in northern Tanzania, who still practise traditional foraging. Post-menopausal grandmothers were found to use foraged tubers to support both themselves and the children of their daughters, releasing the daughters to become pregnant again.

Developments in molecular biology have meant that events in the evolution of Homo sapiens can be recorded. Once the genetic code was deciphered this eliminated the need to depend on phenotypic proxies for information about propinquity. Gene frequencies were used in the first attempts to relate regional populations. It is hoped that new and more precise analytical methods will be developed, which will add accuracy and precision to attempts to trace modern human evolution.

Evidence exists of a link between the hominid group Paranthropus and stone tool manufacture between around 2.5 and 1.5 million years ago. There is data showing that Paranthropus aethiopicus/boisei existed in Ethiopia's Omo region during the same approximate time period. These relate to new evidence from Gona in Ethiopia, which reveals that the onset of tool manufacture dates back to 2.5 million years ago and a recent report that stone tools were discovered in 'close association' with a jawbone from an early example of the Homo species at a nearby 2.3 million-year-old site in Hadar.

Excavations of the hominid remains in China reveal that the lineage moved to Asia from Africa about 1.9 million years ago. At Longgupo cave in China, dating experiments indicate that the fossils are a species similar to Homo (H.) ergaster, found only in Africa. The evidence supports the fact that hominids moved to China in the Pliocene era. The hominid lineage is considered to originate in Africa but there is no strong evidence of when the movement out of the country took place.

Tim White and his colleagues have discovered a fossil of a child's jaw from Aramis, Ethiopia, that is one of the earliest hominids dated to 4.4 million years ago. The fossil forms a part of other hominids called Australopithecus ramidus, dated to the same period. These fossils are older than the Australopithecus afarensis, which were considered to be the oldest, by about a million years. The Australopithecus ramidus will provide information on the link between the African ape lineage and modern humans, which is essential for palaeoanthropological research.

Hominid Corridor Research Project members surveyed regions between east and South Africa to discover fossils which indicate mammalian response to climactic variations and species interchanges in the two regions. Earlier available fossils from eastern African Rift Valley and southern Africa are 3, 000 kilometers away from each other. Similarities between the fossils suggested that they must have had faunal exchanges.

Two new studies in bipedalism are a step forward in our understanding of its evolution and uses. P.E. Wheeler's physiological model shows that bipedalism would reduce heat stress and water use in a 35-kg hominid, and that a naked verses haired skin is superior for cooling only when radiant heat is reduced. K.D. Hunt's behavioral study of chimpanzees shows that most of their bipedal activity is postural, not locomotive, and occurs in or near trees, not the savannah.

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]

Author(s): Bernard Wood [1] Human Evolution Through Developmental Change by Nancy Minugh-Purvis & Kenneth J. McNamara Johns Hopkins University Press: 2002. 536 pp. $59.95, £40 'Are humans really our closest [...]