CHALLENGES TO THE EVOLUTIONARY SYNTHESIS Richard M. Burian Department of Philosophy Virginia Polytechnic Institute and State University Blacksburg, VA 24061 Lightly corrected submission draft of a paper published in Evolutionary Biology 23 (1988): 247-269. Neo-Darwinism has been rightly construed more as a treaty than a theory because it laid down terms that allowed evolutionists and practitioners of the new science of genetics (and more generally molecular biology) to work together under common presuppositions. Evolutionists, in repudiation of their earlier flirtations with Lamarckism, accepted Weismannism; while geneticists, abandoning stress on macromutations, accepted the gradualist assumptions of the Darwinian tradition (Mayr and Provine, 1980). What made these agreements possible was a common analytical framework based on the amplification of Mendel's Rules to the level of populations by way of the Hardy-Weinberg Equilibrium Formula, according to which gene frequencies could be presumed to remain the same over successive generations unless and until exogenous forces caused one genetic variant to be preferred to another. Depew and Weber, (1988, p. 317) The term 'evolutionary synthesis' was introduced by Julian Huxley in Evolution: the Modern Synthesis (1942) to designate the general acceptance of two conclusions: gradual evolution can be explained in terms of small genetic changes ('mutations') and recombination, and the ordering of the variation by natural selection; and the observed evolutionary phenomena, particularly macroevolutionary processes and speciation, can be explained in a manner that is consistent with the known genetic mechanisms. Mayr in Mayr and Provine, 1980, p. 1, quoted in Eldredge, p. 5 Our goal [in soliciting these essays] is to examine what contributions, if any, can be made by a philosophical reexamination of the underlying assumptions implicit in classical and current evolutionary theory. Is evolution at a crossroads, paraphrasing the title of a recent book? If it is, what alternative assumptions will best guide future research on evolution into new and fruitful directions? Max Hecht, from the letter inviting this essay Introduction This essay offers a perspective on some current disputes regarding the nature and value of the evolutionary synthesis and the theoretical foundations of evolutionary theory. 1 I agree with Depew and Weber's characterization: the synthetic theory of evolution is not mainly a predictive or retrodictive theory, but a treaty favoring work within the confines of a particular research 1 The present article is an essay review of four books, namely Eldredge (1985), Ho and Saunders (1984), Pollard (1984), and Reid (1985). These volumes will be cited without date references; all other citations will include dates. I have taken Max Hecht's inquiry, used as an epigraph, seriously; accordingly I have looked far beyond these books in discussing the content, value, and status of the so-called synthetic theory of evolution.