Frank H. T. Rhodes

Darwinian gradualism and its limits: The development of Darwin's views on the rate and pattern of evolutionary change

ConclusionThe major tenets of the recent hypothesis of punctuated equilibrium are explicit in Darwins writing. His notes from 1837–1838 contain references to stasis and rapid change. In the first edition of the Origin (1859), Darwin described the importance of isolation of local varieties in the process of speciation. His views on the tempo of speciation were influenced by Hugh Falconer and also, perhaps, by Edward Suess (1831–1914). It is paradoxical that, although both topics were recorded in his unpublished notes of 1837–1838, the second was not explicitly and fully discussed until the fourth edition of the Origin (1866). While no wholly satisfactory explanation of this paradox suggests itself, it seems probable that Falconers work on the persistence of fossil species of elephant helped Darwin to see the wider significance of the tempo of evolution for his general theory.

Darwin's search for a theory of the earth: symmetry, simplicity and speculation

1990 marked the 150th anniversary of the publication of Charles Darwins first major scientific theory. The paper, first presented by Darwin to the Geological Society of London on 7 March 1838, was entitled ‘On the Connexion of Certain Volcanic Phenomena and on the Formation of Mountain-Chains and the Effects of Continental Elevations.’ The paper was a remarkable attempt to develop a global tectonic synthesis. It was the culmination of a period of intensive geological activity by Darwin – then twenty-nine – who had returned from the Beagle voyage only eighteen months previously. The present article reviews the development of Darwins views, their impact upon his contemporaries, their role in shaping his later views on the origin of species, and their significance in scientific theory-making. It draws, in part, on Darwins unpublished geological notes and jottings. This paper, and the papers by Sandra Herbert and James Secord that accompany it, were delivered at a symposium which I organized at the Geological Society of London on 31 October 1988 to mark the 150th anniversary of the reading of Darwins paper.

Statistical analysis of British Carboniferous conodont faunas

Three lines of evidence are reviewed that suggest conodont animals contained multielement conodont assemblages in life. Reconstruction of the original multi-element assemblages of conodonts from the Cleistopora (K) and Zaphrentis (Z) Zones of the North Crop of the South Wales Coalfield is attempted using the Centclass programme on a Control Data 3600 computer. Two methods are described which are of use in assemblage reconstruction. Polythetic cluster analysis, first developed for use in ecological surveys, provides dendrograms from which the level of association of individual elements may be determined. This indicates common occurrences of elements and can be supplemented by comparisons of total stratigraphic range and relative frequency of elements. Thirteen groups are recognized which are compared with assemblage models based on assemblages preserved in situ on shale bedding planes. Group 8 compares with a basic duboisellid (Class C) type of assemblage. Groups 5 and 6 do not appear to represent meaningful groups. All other groups represent either complete or partial Lochreia type Class A assemblages.

British Lower Carboniferous Conodont Faunas and Their Value in Correlation: ABSTRACT

Six hundred samples of limestone and shale from the Lower Carboniferous of southwestern England and Wales and central Scotland were processed for conodonts. The samples yielded over 25,000 identifiable specimens, referable to 170 species, representing 26 genera. Two genera, 22 species, and 12 subspecies are new. The faunas have been divided into a succession of 16 conodont assemblage zones, which are used as a basis for correlation between standard sections in various Carboniferous provinces of Great Britain. They also make possible correlation with the successions in Germany and North America, to which faunas there is a strong general similarity. Local differences are attributed to sedimentary breaks, limited geographic distribution, and conodont phylogeny. In the southwestern province of Britain, the greater part of the K zone is correlated with the Cu-I goniatite zone of Germany; the uppermost K, Z, and C zones with the Cu-II zone; and the C2S1, S2, D1, D2, and lower D3 zones with the Cu-III zone. The upper D3 zone is of E1 (Namurian) age. The upper part of the Calciferous Sandstone Series of the Midland Valley of Scotland is of Cu-III ^agr age, the Lower Limestone Group of Cu-III s/^ggr age, and the Upper Limestone Group of E1/E2 (Namurian) age. End_of_Article - Last_Page 604------------