Reflections on the four facets of symmetry: how physics exemplifies rational thinking

In contemporary theoretical physics, the powerful notion of symmetry stands for a web of intricate meanings among which I identify four clusters associated with the notion of transformation, comprehension, invariance and projection. While their interrelations are examined closely, these four facets of symmetry are scrutinised one after the other in great detail. This decomposition allows us to examine closely the multiple different roles symmetry plays in many places in physics. Furthermore, some connections with others disciplines like neurobiology, epistemology, cognitive sciences and, not least, philosophy are proposed in an attempt to show that symmetry can be an organising principle also in these fields

Identifying the Collector: Evidence for Human Processing of the Cape Dune Mole-Rat,Bathyergus suillus, from Blombos Cave, Southern Cape, South Africa

The remains of Cape dune mole-rats are commonly found in archaeological sites in the Cape but identifying the agents responsible for their introduction, namely humans, raptors or other carnivores, has until now been largely speculative. An examination of mole-rats caught and cooked by contemporary farmworkers in the southern Cape showed distinctive burning patterns on the incisors and premaxillae. Similar charring is observable on mole-rat post-cranial bones recovered from the Later Stone Age layers at Blombos Cave suggesting that mole-rats were brought to this site by humans, cooked in the ethnographically observed manner and eaten. Extending this study to other archaeological sites in the Cape may help identify the prehistoric collectors of these animals

Blombos Cave, Southern Cape, South Africa: Preliminary Report on the 1992–1999 Excavations of the Middle Stone Age Levels

The Later- and Middle Stone Age levels at Blombos Cave (BBC) were excavated over four field seasons between 1992 and 1999. Here we report on the results from the Middle Stone Age (MSA) levels. The taphonomy and depositional history of the MSA levels is complex due to faulting, folding and spalling. Careful observations during excavation have assisted in understanding some of these taphonomic and site formation processes; microstratigraphic analysis, currently in progress, will add to this information. The uppermost MSA level, the Still Bay phase, contains high densities of bifacial points, the fossile directeur of the Still Bay Industry. Placing the Still Bay within the MSA culture sequence has been problematic in the past because Still Bay assemblages are rarely found in situ and previous excavations were inadequately recorded. However with the regional data discussed in the text, the Still Bay can be securely placed before the Howiesons Poort dated at 65–70 ka. Flaked stone makes up the greatest proportion of all artefacts with the highest incidence of retouch and use of fine grained, non-local materials found in the Still Bay levels. The ochre assemblage is remarkable for the mass of material compared to other MSA sites. Finds uncommon in an MSA context are two pieces of ochre from the Still Bay phase engraved with a geometric design; a fragment of deliberately engraved bone; also, 28 shaped and polished bone tools recovered mainly from a phase just below the Still Bay. Blombos Cave is the first site where well preserved faunal remains have been recovered in association with the Still Bay allowing for unique insights into human subsistence behaviour and palaeoenvironmental reconstruction. Large fish bones, marine shells, seals and dolphins attest to extensive exploitation of aquatic resources and a wide range of terrestrial animals were hunted and gathered. The few human teeth recovered are heavily worn and damaged thus the issue of morphological modernity cannot be addressed. The BBC findings are a useful ad