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Gradualism, in biology, holds that evolution occurs through the accumulation of slight modifications over a period of generations. This is in contrast to saltationism, which holds that evolution occurs through large changes, possibly in a single generation.
Gradualism holds that every individual is the same species as its parents, and that there is no clear line of demarcation between the old species and the new species. It holds that the species is not a fixed type, and that it is the population, not the individual, that evolves.
"Support for gradualism derives from the fact that many, probably most, evolutionary processes are indeed gradual and incremental....However, it is one thing to believe that gradual processes predominate in nature and quite another to hold that all evolutionary processes must be gradual. The issue is, after all, simply an empirical one; even if no nongradual changes were ever witnessed, one could never exclude the possibility that the next evolutionary process to be uncovered might be nongradual." Examples include sudden adaptation due to natural disaster, preadaptations and exaptations (Gould and Vrba 1982), and possibly, syntax and language, which being hierarchical could not have been gradual, "the difference between flat structure (beads on a wire) and hierarchyical structure is absolute" (Bickerton 2000, p.159). One example of preadaptation is insect flight as insects were originally exclusively terrestrial, some with fanlike structures for cooling which were selected for until they were large and efficient enough to allow flight (ibid, p.160).
See also: punctuated equilibria
- Bickerton, Derek (2000). "Biomusicology and Language Evolution Studies", The Origins of Music. Cambridge, Mass: A Bradford Book, The MIT Press. ISBN 0262232065.
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