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The intended coup de gr?ce of your article on Stephen Jay Gould's latest book ("Biology's unedited crusader", THES , April 26), that "cladistics made punctuated equilibrium redundant a long time ago", is nonsense. Cladistics is a way of reconstructing the hierarchy of branching nodes in evolutionary trees, regardless of the mode of speciation, which is what punctuated equilibrium is about. They address separate issues and are compatible.

Another howler is the contention that "the fossil record remains as free of transitional forms as ever". Microevolutionary studies stimulated by Gould's theory have revealed many transitional fossil forms.

Gould's ideas on the hierarchical nature of evolutionary processes are still pertinent wherever one stands on them.

Peter Skelton
Chair, 'Evolution' course, Open University;
Peter Sheldon
Chair, 'Fossils and the history of life' course, Open University;
Tony Hallam
School of Earth Sciences University of Birmingham