Evidence of fatal skeletal injuries on Malapa Hominins 1 and 2

Malapa is one of the richest early hominin sites in Africa and the discovery site of the hominin species, Australopithecus sediba. The holotype and paratype (Malapa Hominin 1 and 2, or MH1 and MH2, respectively) skeletons are among the most complete in the early hominin record. Dating to approximately two million years BP, MH1 and MH2 are hypothesized to have fallen into a natural pit trap. All fractures evident on MH1 and MH2 skeletons were evaluated and separated based on wet and dry bone fracture morphology/characteristics. Most observed fractures are post-depositional, but those in the right upper limb of the adult hominin strongly indicate active resistance to an impact, while those in the juvenile hominin mandible are consistent with a blow to the face. The presence of skeletal trauma independently supports the falling hypothesis and supplies the first evidence for the manner of death of an australopith in the fossil record that is not attributed to predation or natural death

Exhumation of high-pressure granulites and the role of lower crustal advection in the North China Craton near Datong

Granulites in the Datong-Huai'an area of North China are characterized by high P-T assemblages (14 -16 kbar, similar to 900 degrees C) that underwent decompression cooling to similar to 7 kbar and similar to 800 degrees C during a 2500-2400 Ma tectonic event. Nearly all structures in the grantilites developed during the retrograde exhumation history, and can be subdivided into: (I) the stratigraphically lower,'lower structural domain' that is characterized by complex folding with 55-10 km wide domes surrounded by concentric troughs, preserving concentric lineation patterns; and (2) the stratigraphically higher 'upper structural domain' that is characterized by a planar gneissic foliation, upright folds and a constant, shallowly SW plunging, lineation pattern. During exhumation rocks probably passed from the 'lower' into the 'upper structural domain'. Domes, recumbent folds and transposition fabrics resulted from a dynamic interplay between vertical (advective) flow and horizontal flattening. The 'lower structural domain' preserves structures reflecting the dominance of vertical flow while the 'upper structural domain' preserves structures that resulted from flattening and lateral flow. Horizontal flattening and lateral flow of domal structures led to total destruction of the domal geometries by transposition in a younger, horizontal gneissic layering. The process of doming, flattening and transposition repeated itself as advective exhumation of the high-pressure rocks progressed. Horizontal fabrics appear the more stable geometry and domes progressively degenerated into horizontal lensoidal shapes, probably as a result of the low viscosities of the granulites. Exhumation of lower crustal material via solid-state advective flow implies that vertical crustal movements of at least part of the crust occurred independently of isostatic readjustments. P-T paths, characterized by isothermal decompression over a large pressure range, can therefore be interpreted to result from processes that are independent of crustal thickening, erosion and tectonic denudation. (C) 1997 Elsevier Science Ltd

U–Pb-dated flowstones restrict South African early hominin record to dry climate phases

The Cradle of Humankind (Cradle) in South Africa preserves a rich collection of fossil hominins representing Australopithecus, Paranthropus and Homo1. The ages of these fossils are contentious2,3,4 and have compromised the degree to which the South African hominin record can be used to test hypotheses of human evolution. However, uranium–lead (U–Pb) analyses of horizontally bedded layers of calcium carbonate (flowstone) provide a potential opportunity to obtain a robust chronology5. Flowstones are ubiquitous cave features and provide a palaeoclimatic context, because they grow only during phases of increased effective precipitation6,7, ideally in closed caves. Here we show that flowstones from eight Cradle caves date to six narrow time intervals between 3.2 and 1.3 million years ago. We use a kernel density estimate to combine 29 U–Pb ages into a single record of flowstone growth intervals. We interpret these as major wet phases, when an increased water supply, more extensive vegetation cover and at least partially closed caves allowed for undisturbed, semi-continuous growth of the flowstones. The intervening times represent substantially drier phases, during which fossils of hominins and other fossils accumulated in open caves. Fossil preservation, restricted to drier intervals, thus biases the view of hominin evolutionary history and behaviour, and places the hominins in a community of comparatively dry-adapted fauna. Although the periods of cave closure leave temporal gaps in the South African fossil record, the flowstones themselves provide valuable insights into both local and pan-African climate variability