2nd Year. Final honour School in Biological Sciences: Principles of Palaeobiology
This course is about the principles underlying the use of the direct historical evidence of fossils on the great questions of evolutionary biology – how remains of long dead organisms can still tell us interesting things about how evolution works. Despite its notorious incompleteness and therefore too poor a temporal resolution for illustrating much about evolutionary change below the level of speciation, fossils provide the only evidence, however limited, about certain aspects evolution. The overriding thing is the almost unimaginable difference in temporal scale between the "ecological" time scale that neontologists work in (years to decades) and the "geological" timescale that palaeontologists work in (tens of thousands to thousands of millions of years). This, the epistemological gap, leads to a great deal of mutual misunderstanding between the two traditions of evolutionary study. There are in fact some extremely important evolutionary phenomena that have only been revealed because of the existence of the fossil record, and which indeed we might not even suspect without it, viz:
The enormous longevity of a species. Typically between 1 million and 25 million years of what is called 'stasis'.
The role of species-level rather than organism-level characters. Not all of the evolutionary pattern can be accounted for solely in terms of microevolutionary processes.
The extent of taxonomic turnover. At every level of classification, taxa arise, flourish, disappear, and are replaced by new ones. This points to long-term ecological phenomena not readily apparent from modern ecosystems.
Mass extinctions. There were frequent phases of rapid, global, and taxonomically widespread greatly elevated extinction rates, with over 30%, and as high as 90% loss of species, indicating extraordinarily severe perturbations of the global ecosystem from time to time.
The origin of new higher taxa. How major evolutionary transitions occur is one of the most neglected areas of evolutionary biology, mainly because of the mathematical intractability, but the question remains: are there unusual genetic events and/or environmental circumstances associated with the long treks through morphospace that culminate in a radically new kind of organism?
Synopses of lectures
Lectures 1 & 2
What use are fossils? Organismic incompleteness and how to reconstruct functional biology and to recognise species. Stratigraphic incompleteness and how it can distort the record: the concepts of completeness, resolution and adequacy. Ecological incompleteness: methods for reconstruction from a fossil assemblage of the one-time living community and its environment – palaeoautecology, palynology, taphonomy, sedimentology, geochemistry, and stable isotope analysis.
The epistemological gap, pattern and process, and the nature of palaeobiological theories. Fossils and phylogeny or, if only we had more fossils! How to use, and how not to use fossils in phylogenetic reconstruction. Do the relative ages of the fossils help?
What the fossil record can add to understanding speciation – its frequency and its time-course. The empirical basis and the implications of the theory of puncuated equilibria. Species selection as a hypotheses of process and the arguments for and against it. The controversial idea of evolution at different hierarchical levels.
Taxonomic turnover. The global Phanerozoic pattern of diversity change and its possible causes. Individual clade histories. Inter-clade relationships: competition, opportunism, and correlated stasis.
Lectures 7 & 8
The origin of new higher taxa: the ultimate question. Is it a different process from normal evolution, or are there special genetic or environmental circumstances? The increasing role of molecular developmental genetics in hypotheses of the origin of new taxa – 'evodevo'. The example of the Cambrian explosion and the origin of the invertebrate phyla.
Kemp, T.S. 1999. Fossils and evolution. OUP.
Briggs, D.E.G. and Crowther, P.R. 2003. Palaeobiology II.