E VERY PERIOD in the history of civilized man was dominated by a definite set of ideas or ideologies. This is as true for the ancient Greeks as for Christianity, the Renaissance, the Scientific Revolution, the Enlightenment, and our modern times. It is a challenging question to ask what the source is of the dominating ideas of our present era. One can ask this question also in different terms. For instance, which books have had the greatest impact on current thinking? Inevitably, the Bible would have to be mentioned in the first place. Up to 1989, when the bankruptcy of Marxism was declared, Karl Marx's Das Kapital would clearly have been in second place, and it is still the dominating influence in many parts of the world. However, Darwin's On the Origin of Species (1859) must surely be mentioned in the next place. I hope to be able to show that this position is justified not only because Darwin more than anyone else was responsible for the acceptance of a secular explanation of the world, but also because he revolutionized our thinking about the nature of this world in surprisingly many other ways.

One of the most basic questions of evolutionary biology is what objects are being selected in the process of natural selection? Lloyd (1) found nearly 200 references to books and papers by biologists and philosophers, beginning with Darwin, that treated this question, “and these represent just a fraction of the literature on the topic,” she reports. Indeed in the recent literature the answer to this question has been argued each year by at least a half dozen authors. [This analysis is not a review paper. The listing of the literature is therefore reduced to a minimum. All relevant titles can be found in the works of Lloyd (1) and Brandon (2).] An analysis of this literature has convinced me that some basic conceptual differences, as well as the opponents’ failure to adhere to a rigorous definition of the terms, are the major causes of the confusion. Evidently a new approach that attempts a careful critique of the arguments of the opposing parties is needed. This is what I am attempting here.

Philosophers of science have claimed that the position of biology among the sciences is the most prominent and controversial issue of the philosophy of biology. Some authors consider biology merely a "province" of physics and reducible to physics, others uphold the autonomy of biology, while still others have decided that biology lacks the rigor to justify being considered a genuine science. In my own analysis of this problem. I have concluded that the science of biology has all the attributes of a genuine science, as well as a number of other characteristics restricted to biology. These characteristics are listed and discussed. They justify ranking biology as an autonomous science, just as autonomous as physics and many other sciences.

I analyze a number of widespread misconceptions concerning species. The species category, defined by a concept, denotes the rank of a species taxon in the Linnaean hierarchy. Biological species are reproducing isolated from each other, which protects the integrity of their genotypes. Degree of morphological difference is not an appropriate species definition. Unequal rates of evolution of different characters and lack of information on the mating potential of isolated populations are the major difficulties in the demarcation of species taxa.

Every period in the history of civilized humans was dominated by a definite set of ideas or ideologies. This is as true for the ancient Greeks as for Christianity, the Renaissance, the Scientific Revolution, the Enlightenment, and modern times. It is a challenging question to ask what the source is of the dominating ideas of the present era. One can ask this question also in different terms. For instance, which books have had the greatest impact on current thinking? Inevitably, the Bible would have to be mentioned in first place. Before 1989, when the bankruptcy of Marxism was declared, Karl Marx's Das Kapital would clearly have been in second place, and it is still a dominating influence in many parts of the world. Sigmund Freud has been in and out of favor. Albert Einstein's biographer Abraham Pais made the exuberant claim that Einstein's theories “have profoundly changed the way modern men and women think about the phenomena of inanimate nature.” No sooner had Pais said this, though, than he recognized the exaggeration. “It would actually be better to say ‘modern scientists’ than ‘modern men and woman,’” he wrote, because one needs schooling in the physicalist style of thought and mathematical techniques to appreciate Einstein's contributions. Indeed I doubt that any of the great discoveries in the physics of the 1920s had any influence whatsoever on the thinking of the average person. However, the situation is different with Darwin's On the Origin of Species (1859).

Scientific revolutions in biology do not conform to the description of such revolutions as given by T. Kuhn. Instead, several paradigms may coexist simultaneously for long periods of time, and succeeding paradigms are not necessarily incommensurable. Biological revolutions are not separated by long periods of normal science; rather, there are always minor revolutions and theory changes of various magnitude. Kuhn's theory is in good agreement with essentialistic philosophy, while theory change in biology fits Darwinian evolutionary epistemology, consisting of variation (the continuing proposal for new theories) and selection (the survival of the successful ones). Nowadays there is very little dissent (at least among scientists) from the thesis that science makes steady advances and that, as a result of these advances, we are gaining an ever improving understanding of the world. What is, however, highly controversial is how these advances occur. This controversy occupies a large portion of the literature of contemporary philosophy of science. Leaving a number of minor movements aside, one can distinguish two major schools, Kuhn's theory of scientific revolutions (and normal science) and Darwinian evolutionary epistemology. I shall not discuss the latter.1

Many angiosperm species produce cones of anthers which release pollen through pores in response to vibration by pollinating bees (“buzz-pollination”). Anther cones of varying degrees of strength are a defining morphological trait for the genus Solanum. Anthers arranged in a robust (‘pepper pot’) cone are restricted to a single clade within the genus, and may therefore be assumed to be monophyletic. We show that in some species within this clade, such as tomato (Solanum lycopersicum), the anther cone is held together by interlocking hairs (trichomes) along the edges of the anthers. In other species within the clade, such as woody nightshade (Solanum dulcamara), the expanded anther surfaces are closely appressed to form the tightly bound cone, strengthened by extracellular secretions. Ectopic expression of the MIXTA gene from Antirrhinum majus in S. dulcamara results in the formation of ectopic trichomes on the anthers which cause the cone to disintegrate. Therefore, these two species produce the same macroscopic structure through two mutually exclusive developmental routes and the robust anther cone is derived differently within the clade. This example demonstrates that convergence between closely related species can be easily mistaken for homology, and may thus be underestimated.

A theory may be invalid, not owing to erroneous observations or the invocation of an inappropriate law, but because of the use of equivocal terms. This is demonstrated for Darwin's failed model of sympatric speciation through the principle of divergence.

There has not been another scientific revolution that caused as much turmoil and dissension as the darwinian one. For almost 80 years it was again and again pronounced to be a failure and to be totally refuted, and at least three major alternatives were proposed to replace it. Yet, in the 1930s-1940s the opposing views were quickly and decisively refuted and a largely unified evolutionary theory emerged. Why and how this happened, however, is still rather controversial.

Up to the end of the 19th century the typological species concept was universally accepted, in which degree of morphological difference was the species criterion. This concept was increasingly replaced (particularly in zoology) beginning around 1900 by the biological species concept because the criterion of morphological distinctness broke down in the case of sibling species and of highly distinct intrapopulational variants. The yardstick for the recognition of biological species is the noninterbreeding of coexisting species in a local situation. This yardstick can be applied to isolated populations only by inference. It is discussed whether the making of such inferences is too arbitrary to be acceptable. A local flora is analyzed to determine whether polyploidy, apomixis, hybridization, and other deviations from regular sexual reproduction are sufficiently frequent in plants to make the biological species concept illusory. It is found that the number of difficulties is small, validating use of the sympatric situation as yardstick for the ranking of allopatric populations.

Previous articleNext article No AccessCommentaryHaldane's Causes of Evolution After 60 YearsErnst MayrErnst Mayr Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 67, Number 2Jun., 1992 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/417554 Views: 1Total views on this site Citations: 8Citations are reported from Crossref Copyright 1992 The University of ChicagoPDF download Crossref reports the following articles citing this article:Sahotra Sarkar Haldane’s The causes of evolution and the Modern Synthesis in evolutionary biology, Journal of Genetics 96, no.55 (Nov 2017): 753–763.https://doi.org/10.1007/s12041-017-0840-5Veena Rao, Vidyanand Nanjundiah Ernst Mayr’s interactions with J. B. S. Haldane, History and Philosophy of the Life Sciences 38, no.11 (Feb 2016): 138–150.https://doi.org/10.1007/s40656-016-0098-xVeena Rao, Vidyanand Nanjundiah J. B. S. Haldane, Ernst Mayr and the Beanbag Genetics Dispute, Journal of the History of Biology 44, no.22 (Mar 2010): 233–281.https://doi.org/10.1007/s10739-010-9229-5Sahotra Sarkar HALDANE AND THE EMERGENCE OF MODERN EVOLUTIONARY THEORY, (Jan 2007): 49–86.https://doi.org/10.1016/B978-044451543-8/50005-8Sahotra Sarkar In memoriam: Ernst Mayr (1904–2005), Journal of Biosciences 30, no.44 (Sep 2005): 415–418.https://doi.org/10.1007/BF02703712Ralph Shelton Genetics News—Quantitative and Molecular Genetics in Complex Disorders, Perspectives on Speech Science and Orofacial Disorders 9, no.11 (Nov 1999): 8–11.https://doi.org/10.1044/ssod9.1.8Jerry A. Coyne ERNST MAYR AND THE ORIGIN OF SPECIES, Evolution 48, no.11 (May 2017): 19–30.https://doi.org/10.1111/j.1558-5646.1994.tb01290.x Arthur M. Shapiro Haldane, Marxism, and the Conduct of Research, The Quarterly Review of Biology 68, no.11 (Oct 2015): 69–77.https://doi.org/10.1086/417912

Perhaps no other ideology has influenced biology more profoundly than teleological thinking. In one form or another it was the prevailing world view prior to Darwin. (Indeed it is one of the relatively few world views seriously considered by western man.) Appropriately, the discussion of teleology occupies considerable space (10-14%) in several recent philosophies of biology.' Such a finalistic world view had many roots. It is reflected by the millenarian beliefs of many Christians, by the enthusiasm for progress promoted by the Enlightenment, by transformationist evolutionism, and by everybody's hope for a better future. However, such a finalistic world view was only one of several widely adopted Weltanschauungen. Grossly simplifying a far more complex picture, one can perhaps distinguish, in the period prior to Darwin, three ways of looking at the world: 1. A recently created and constant world. This was the orthodox Christian dogma, which, however, by 1859 had largely lost its credibility, at least among philosophers and scientists.2 2. An eternal and either constant or cycling world, exhibiting no constant direction or goal. Everything in such a world, as asserted by Democritus and his followers, is due to chance or necessity, with chance by far the more important factor. There is no room for teleology in this world view, everything being due to chance or causal mechanisms. It allows for change, but such change is not directional; it is not an evolution. This view gained some support during the Scientific Revolution and the Enlightenment, but remained very much a minority view until the nineteenth century. A rather pronounced polarization developed from the seventeenth to the nineteenth centuries, between the strict mechanists,