The sudden appearance in the fossil record of the major animal phyla apparently records a phase of unparalleled, rapid evolution at the base of the Cambrian period, 545 Myr ago. This has become known as the Cambrian evolutionary ‘explosion’, and has fuelled speculation about unique evolutionary processes operating at that time. The acceptance of the palaeontological evidence as a true reflection of the evolutionary narrative has been criticised in two ways: from a reappraisal of the phylogenetic relationships of the early (...) fossils, and from predicitions of molecular divergence times, based on six appropriate metazoan genes. Phylogenetic analysis of the arthropods implies an earlier, Precambrian history for most clades, and hence an extensive period of cladogenesis unrecorded by fossils. A similar argument can be applied to molluscs, lophophorates and deuterostomes. Molecular evidence implies divergence between clades to at least 1000 Myr ago. The apparent paradox between the sudden appearance of recognisable metazoans and their extended evolutionary history might be explained by a sudden Cambrian increase in body size, which was accompanied by skeletisation. A new paradigm suggests that the ‘explosion’ in the record may have been decoupled from the evolutionary innovation. (shrink)

Philosothons are events in which students practise Community of Philosophical Inquiry, usually with awards being made using three criteria: critical thinking, creative thinking and collaboration. This seems to generate a tension. On the one hand it recognises collaboration as a valued trait; on the other hand, the element of competition may seem antithetical to collaboration. There are various possible considerations relevant to this apparent problem. We can pose them as seven questions. One, do the awards really recognise the best performers? (...) Two, do the students and teachers see the awards as fair and reasonable? Three, do the awards recognise cooperation as a valuable contribution? Four, do Philosothons generate enthusiasm and goodwill? Five, might awards motivate students to try harder to do well? Six, if competition is normal in society, does it follow that it is justified as part of the Philosothon? Seven, do awards have a role in bringing the event to a climax? In this article, we will develop and evaluate the arguments suggested by these questions. Our conclusion is that the competitive element in the Philosothon is not antithetical to the collaborative ideal of philosophy. (shrink)

In a recent paper,(1) palaeontologist Mike Benton claimed that our ability to reconstruct accurately the tree of Life may not have improved significantly over the last 100 years. This implies that the cladistic and molecular revolutions may have promulgated as much bad “black box” science as rigorous investigation. Benton's assessment was based on the extent to which cladograms (typically constructed with reference only to distributions of character states) convey the same narrative as the geochronological ages of fossil taxa (an independent (...) data set). Fossil record quality varies greatly between major clades, and the palaeontological dating “yardstick” may be more appropriate for some groups than others. BioEssays 24:203–207, 2002. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/bies.10065. (shrink)

Considering the enormous diversity of living organisms, representing mostly untapped resources for studying ecological, ontogenetic and phylogenetic patterns and processes, why should evolutionary biologists concern themselves with the remains of animals and plants that died out tens or even hundreds of millions of years ago? The reason is that important new insights into some of the most vexing evolutionary questions are being revealed at the interfaces of palaeontology, developmental biology and molecular biology. Attempts to synthesise information from these disciplines, however, (...) often encounter their greatest hurdles in considerations of the radiation of the Metazoa. Ongoing challenges relate to the origins of body plans, the relationships of the metazoan phyla and the timing of major evolutionary radiations. Palaeontology not only has its own unique contributions to the study of evolutionary processes, but provides a lynchpin for many of the emerging techniques. BioEssays 22:1142–1152, 2000. © 2000 John Wiley & Sons, Inc. (shrink)