Sir

In his Turning Points essay “Learning from the Altmeister”, Axel Meyer highlights the 100th birthday this year of the great evolutionist Ernst Mayr (Nature 428, 897; 200410.1038/428897a). Yet the other major centenary for evolutionary biology has been overlooked, both by Meyer and in your anniversary Commentary article “1904 and all that” (Nature 426, 761–764; 2003). Edward Bagnall Poulton's paper “What is a Species?” (Proc. Entomol. Soc. Lond. 1903, lxxvii–cxvi; 1904) was the first to grapple exclusively with the problem of species in an evolutionary framework. Poulton's paper, a version of his January 1904 presidential address to the Entomological Society of London, laid out the research programme for speciation largely adopted today.

I do not wish to belittle the work of Mayr and the geneticist Theodosius Dobzhansky — but our impression that they solved the species problem is illusory. They were merely the ones who translated it from the technical literature, enunciating much more clearly than before what had become the prevailing view of species among those who had thought about the problem.

Both Mayr and Dobzhansky were strongly influenced by Poulton, as well as by Poulton's friend Karl Jordan, also a Fellow of the Entomological Society, and both cited their work. Mayr was to form his views on species and speciation, and particularly the ‘biological species concept’, nearly 40 years after Poulton's pioneering argument that species were reproductively isolated populations.

Yet the historical links go back even further. In December 1903, shortly before Poulton's lecture, Alfred Russel Wallace gave him a signed book on mimicry and speciation. This contained a reprint of Wallace's 1865 paper on Asian Papilio butterflies: the first to recognize that the female mimics of poisonous swallowtails were members of the same species as non-mimetic males.

Wallace also made the first careful analysis by a darwinist of ‘varieties’ below the species level, in particular distinguishing geographic races from reproductively isolated species. Darwin had never provided such an analysis, leaving his definition of species vague. Both Poulton and Jordan worked on Papilio butterflies, and cited Wallace's paper.

So, as well as Mayr's 100th birthday, we should celebrate the centenary of Poulton's paper and his gift from Wallace. These events were as epochal in their way for evolutionary biology as was the understanding of the structure of DNA for genetics.