Exaptation—a Missing Term in the Science of Form | Paleobiology | Cambridge Core (original) (raw)

Abstract

Adaptation has been defined and recognized by two different criteria: historical genesis (features built by natural selection for their present role) and current utility (features now enhancing fitness no matter how they arose). Biologists have often failed to recognize the potential confusion between these different definitions because we have tended to view natural selection as so dominant among evolutionary mechanisms that historical process and current product become one. Yet if many features of organisms are non-adapted, but available for useful cooptation in descendants, then an important concept has no name in our lexicon (and unnamed ideas generally remain unconsidered): features that now enhance fitness but were not built by natural selection for their current role. We propose that such features be called exaptations and that adaptation be restricted, as Darwin suggested, to features built by selection for their current role. We present several examples of exaptation, indicating where a failure to conceptualize such an idea limited the range of hypotheses previously available. We explore several consequences of exaptation and propose a terminological solution to the problem of preadaptation.

References

Abercrombie, M., Hickman, C. H., and Johnson, M. L. 1951. A Dictionary of Biology. 5 th edition, 1966. Hunt Bernard and Co. Ltd., Aylesbury, Great Britain.Google Scholar

Arnold, A. J. and Fristrup, K. 1982. The hierarchical basis for a unified theory of evolution. Paleobiology, in press.Google Scholar

Bock, W. 1967. The use of adaptive characters in avian classification. Proc. XIV Int. Ornith. Cong., Pp. 66–74.Google Scholar

Bock, W. 1979. A synthetic explanation of macroevolutionary change—a reductionistic approach. Bull. Carnegie Mus. Nat. Hist. No. 13:20–69.Google Scholar

Bock, W. J. 1980. The definition and recognition of biological adaptation. Am. Zool. 20:217–227.CrossRefGoogle Scholar

Bock., W. J. and von Wahlert, G. 1965. Adaptation and the form-function complex. Evolution. 10:269–299.CrossRefGoogle Scholar

Britten, R. J. and Davidson, E. H. 1971. Repetitive and non-repetitive DNA sequences and a speculation on the origins of evolutionary novelty. Q. Rev. Biol. 46:111–131.CrossRefGoogle Scholar

Darwin, C. 1859. On the Origin of Species. J. Murray: London.Google Scholar

Dickerson, R. E. and Geis, I. 1969. The Structure and Action of Proteins. Harper and Row; New York.Google Scholar

Doolittle, W. F. and Sapienza, C. 1980. Selfish genes, the phenotype paradigm, and genome evolution. Nature. 254:601–603.CrossRefGoogle Scholar

Duthie, R. B. and Ferguson, A. B. 1973. Mercer's Orthopaedic Surgery. 7thedition. Edward Arnold; London.. 4th edition (first publ. in 1940). John Voelcker Bird Book Fund; Cape Town.Google Scholar

Mivart, St. G. 1871. On the Genesis of Species. MacMillan; London.Google Scholar

Oster, G. 1980. Mechanics, morphogenesis and evolution. Address to Conference on Macroevolution, October 1980, Chicago.Google Scholar

Paterson, H. E. H. 1982. Species as a consequence of sex, in press. Am. Sci.Google Scholar

Pautard, F. G. E. 1961. Calcium, phosphorus, and the origin of backbones. New Sci. 12:364–366.Google Scholar

Pautard, F. G. E. 1962. The molecular-biologic background to the evolution of bone. Clin. Orthopaed. 24:230–244.Google Scholar

Porter, R. MS. Problems in the treatment of ‘madness’ in English science, medicine and literature in the eighteenth century.Google Scholar

Racey, P. A. and Skinner, J. C. 1979. Endocrine aspects of sexual mimicry in spotted hyenas Crocuta crocuta. J. Zool. London. 187:315–326.CrossRefGoogle Scholar

Raup, D. M. and Gould, S. J. 1974. Stochastic simulation and evolution of morphology—towards a nomothetic paleontology. Syst. Zool. 23:305–322.CrossRefGoogle Scholar

Scott, J. D. and Symons, N. B. B. 1977. Introduction to Dental Anatomy. Churchill Livingstone; London.Google Scholar

Vrba, E. S. 1980. Evolution, species and fossils: how does life evolve? S. Afr. J. Sci. 76:61–84.Google Scholar

Williams, G. C. 1966. Adaptation and Natural Selection. Princeton University Press; Princeton, New Jersey.Google Scholar