Species Concepts in Evolution

By some counts, at least 22 different (although maybe somewhat overlapping) species concepts have been proposed within evolutionary circles. Each of them has their own benefits and problems which tend to be associated with the field of science for which they were made. A quick description of the more commonly encountered concepts will serve as an example.

A List of the Major and Some Minor Species Concepts within the Model of Evolution

A List of the Major and Some Minor Species Concepts within the Model of Evolution

The Biological Species Concept was first proposed by Ernst Mayr and defines a species by the possibility of animals interbreeding. This system allows similar groups of animals (with only slight variation) to be grouped into the same species because they would probably interbreed if given the opportunity. This is difficult to test because animal populations that are separated, such as by geographic distance, do not give the opportunity to observe if they will actually interbreed.

The Phylogenetic Species Concept states that geographically separated forms of the same type of animal should be considered distinct species. This does not consider whether the separated groups could interbreed. Instead, it considers that separated groups are independently evolving and therefore will be acquiring a unique genetic history. This has the effect of creating many more species than the Biological Species Concept.

The Morphological Species Concept (also known as the Typological Species concept) is the traditional method of determining species as used by Linnaeus and Darwin. This method categorizes species by phenotype (the observable appearance and anatomical features) of the organism involved. This method usually ignores geographic separation and, therefore, fewer species are made because all of the individual groups are taken as a single species. This method has generally lost favor as genetic studies have increased (except where asexual reproduction occurs).

The study of old or extinct species presents special problems in classification. The exact appearance of the animal is often limited to a few fossil samples and may only include bones. These samples may be separated not only geographically but chronologically, known as chronospecies, as well making classification more difficult as there are different morphs for similar creatures over time. Furthermore, it is not possible to test if one animal fossil could interbreed with another fossil or with a living relative today which makes the Biological Species Concept inapplicable to paleospecies.

Image of an eastern and western meadowlark.

The complications of these conflicting definitions are shown by comparing the Eastern and Western forms of the Meadowlark. These birds, by outward appearance, are almost identical and therefore could be considered a single species under the Morphological Species Concept. However, their ranges overlap and it is found that because their mating songs are different, they do not mate or interbreed together so they become separate species under the Phylogenetic Species Concept.

Last Updated: 2018-07-28
Todd Elder

Todd Elder

Todd Elder has a deep desire to understand and experience Creation. As a Baraminologist, his current research includes developing the Katagenos Species Concept, the Natanzera Classification System, and the Floral Formula Method of determining Plant Kinds. As an author and speaker, his books and seminar materials are designed to encourage a growing relationship with the Creator.
Todd Elder

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