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A Critique of the Species Concept in Biology

Published online by Cambridge University Press:  14 March 2022

Th. Dobzhansky
Th. Dobzhansky*
Affiliation:
California Institute of Technology, Pasadena, California
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Abstract

The species concept is one of the oldest and most fundamental in biology. And yet it is almost universally conceded that no satisfactory definition of what constitutes a species has ever been proposed. The present article is devoted to an attempt to review the status of the problem from a methodological point of view. Since the species is one of the many taxonomic categories, the question of the nature of these categories in general needs to be entered into.

Type
Research Article
Information
Philosophy of Science , Volume 2 , Issue 3 , July 1935 , pp. 344 - 355
Copyright
Copyright © Philosophy of Science Association 1935

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References

1 Since the post-Darwin period a “natural classification” has meant in biology a classification based on the hypothetical common descent of the organisms. This restriction of the meaning of the term is unjustified. The actual mode of descent has been ascertained, and can be ascertained, only for very few groups. But even granting the possibility of establishing the complete phylogenetic history of every organism, it has never been adequately proven that the degree of similarity between the organisms is always proportional to the closeness of their blood relationships. Some palaeontological data cast a grave doubt on this point.

2 This statement applies, of course, only to the discontinuities caused by gene complexes (related species, not to speak about higher categories, differ from each other usually in many genes). Changes in single genes may produce variants so far removed from the original form that their characteristics do not overlap. Discontinuities of this nature may be preserved indefinitely in a panmictic population.