Population thinking

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As population thinking is called in evolutionary biology is a way of thinking that the typological or essentialist thinking faced. The term was introduced by the evolutionary biologist Ernst Mayr in 1959, who wanted to point to what he saw as an essential consequence of Charles Darwin's theory .

The core of population thinking is that organisms are individual members of populations , with the characteristics of each individual being unique. Natural groups of individuals such as biological species are then communities of descent whose similarity to one another is based on their relationship and (in the case of sexually reproducing species) on the exchange of hereditary factors ( gene flow ) during reproduction. Similarities between individuals are therefore not based on an ideal image or type of a species, differences between them not only on the fact that due to disruptive factors or imperfections this is only approximately realized in the individual, but such types have no real existence, they only represent statistical mean values .

For Mayr, population thinking is a fundamental difference between the biological and physical sciences , since physical objects such as atoms, in contrast to biological objects, actually have no individuality, which means that on a fundamental level there are no variations of them - or even transitions between them.

Essentialist and population thinking from a biological point of view

According to Mayr, biology, especially biological taxonomy and systematics, was shaped by typological thinking up to Darwin. The founders of taxonomy such as Carl von Linné were convinced that every species or genus had something like a perfect archetype, the type. Every now and then there are deviations that are actually something like freak births, monstrosities, abnormalities, but in normal cases, if there are no disturbances, each individual approaches the type perfectly. In the philosophical tradition of ancient Greek philosophy, especially Plato and Aristotle (mediated by Porphyrios and the medieval scholastics ), many would have actually considered these types or essences to be more real than the individuals they imperfectly represented. They would have transferred the species (eidos) and the group (genos) of Aristotelian logic to biological objects.

The philosopher of science Karl Popper coined the ( derogatory ) term essentialism for this type of thinking , which was transferred to typological thinking in biology by one of his students, David L. Hull.

Population thinking does not look at objects, but at individuals . Thus, animals and plants seen as individuals who gradually from other members of their to population difference (hence "population thinking"). The species can also show gradual transitions to one another, since in the past they have always emerged from the splitting of previously existing species (see article speciation ). If they currently appear clearly separated from one another, which is actually more common, it is because the previously existing reproductive community has been lost, which has allowed them to diverge in terms of their characteristics, and because individuals with “medium” combinations of characteristics have been disadvantaged by selection were.

Mayr understood the term population , as his definitions clearly show, in a statistical sense. The term population developed from genetics as a real, evolutionary unit on which population biology is based is a special case, but not identical. Individuals are decisive for Mayr's population thinking. The concept of population he used goes back to Francis Galton , Darwin himself hardly used it.

Types and typology in today's biology

Wherever types are mentioned in biology (for example type in the nomenclature , wild type, cultivated form ), this is, according to this view, a relic of the earlier view. It may even suggest that there is an essence, a standard , from which mutations can be classified as deviating. In fact, there are reproductive communities in which not a single individual has a “more justified” or “more genuine” quality than another. Each individual is unique and differs in degrees from its fellow species .

Similar problems are widespread in biology and, according to Ernst Mayr, arise from the incomplete overcoming of essentialist thinking in biology. He therefore calls for the emancipation of biology.

Individual evidence

  1. ↑ Ernst Mayr (1959): Darwin and the evolutionary theory in biology. In: Evolution and anthropolyogy: a centennial appraisal. edited by the Anthropological Society of Washington, 1959, pp. 409-412. Reprinted in: Ernst Mayr: Evolution and the diversity of life: selected essays. 1976 (chapter 3). Reprinted with a new foreword in Elliott Sober (editor): Conceptual Issues in Evolutionary Biology. MIT Press, 1994 (chapter 16)
  2. ^ Carl Chung (2002): On the origin of the typological / population distinction in Ernst Mayr's changing views of species, 1942-1959. Studies in History and Philosophy of Biological and Biomedical Sciences 34: 277-296.
  3. ↑ Ernst Mayr (1996): The autonomy of Biology. The Position of Biology among Sciences. Quarterly Review of Biology 71 (1): 97-106. German version (2002): The autonomy of biology. Naturwissenschaftliche Rundschau, 55 (1): 23–29.
  4. ↑ this is historically disputed today. see. Staffan Müller-Wille (2007): Collection and collation: theory and practice of Linnaean botany. Studies in History and Philosophy of Biological and Biomedical Sciences 38: 541-562., Mary P. Winsor (2006): Linnaeus`s biology was not essentialist. Annals of the Missouri Botanical Garden 93: 2-7.
  5. ^ Elliott Sober: Evolution, Population Thinking, and Essentialism. In: Philosophy of Science. Volume 47, No. 3, 1980, pp. 350-383.
  6. ^ David L. Hull: The effect of essentialism on taxonomy: two thousand years of stasis (1.). In: British Journal for the Philosophy of Science. Volume 15, No. 60, 1965, pp. 314-326. (There are previous uses, but they received no major response.)
  7. ^ Jody Hey (2011): Regarding the Confusion between the Population Concept and Mayr's “Population Thinking”. In: The Quarterly Review of Biology. Volume 86, No. 4, 2011, pp. 253-264, doi : 10.1086 / 662455 .