Theory of species (18TH CENTURY)

(Also referred to as the biological species concept, the isolation species concept, the species concept, and the species taxa.)

Most often associated with Ernst Mayr (1904- ), an evolutionary biologist at Harvard University (but many other biologists have theorized on the subject before and since).

This is the idea that animals and plants can be considered groups of interbreeding natural populations that are reproductively isolated from other such groups.

While the definition of species may appear obvious to a layperson, biologists and philosophers continue to debate its parameters. Some suggest that the wide variety of species concepts being advocated by biologists and philosophers merely proves that there is no unique factor common to all species, and that the idea itself should be abandoned.

Also see: ALLOPATRIC SPECIATION, COHESION SPECIES CONCEPT, EFFECT HYPOTHESIS, GENETIC REVOLUTION, PARAPATRIC SPECIATION, RECOGNITION CONCEPT OF SPECIES, SALTATION SPECIATION, theory of speciation, species essentialism, SYMPATRIC SPECIATION

Source:
M Ereshefsky, The Units of Evolution: Essays on the Nature of Species (Cambridge, Mass., 1992)

On the Origin of Species (or, more completely, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life),^[3] published on 24 November 1859, is a work of scientific literature by Charles Darwin that is considered to be the foundation of evolutionary biology.^[4] Darwin’s book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection. The book presented a body of evidence that the diversity of life arose by common descent through a branching pattern of evolution. Darwin included evidence that he had collected on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence, and experimentation.^[5]

Various evolutionary ideas had already been proposed to explain new findings in biology. There was growing support for such ideas among dissident anatomists and the general public, but during the first half of the 19th century the English scientific establishment was closely tied to the Church of England, while science was part of natural theology. Ideas about the transmutation of species were controversial as they conflicted with the beliefs that species were unchanging parts of a designed hierarchy and that humans were unique, unrelated to other animals. The political and theological implications were intensely debated, but transmutation was not accepted by the scientific mainstream.

The book was written for non-specialist readers and attracted widespread interest upon its publication. As Darwin was an eminent scientist, his findings were taken seriously and the evidence he presented generated scientific, philosophical, and religious discussion. The debate over the book contributed to the campaign by T. H. Huxley and his fellow members of the X Club to secularise science by promoting scientific naturalism. Within two decades there was widespread scientific agreement that evolution, with a branching pattern of common descent, had occurred, but scientists were slow to give natural selection the significance that Darwin thought appropriate. During “the eclipse of Darwinism” from the 1880s to the 1930s, various other mechanisms of evolution were given more credit. With the development of the modern evolutionary synthesis in the 1930s and 1940s, Darwin’s concept of evolutionary adaptation through natural selection became central to modern evolutionary theory, and it has now become the unifying concept of the life sciences.