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No. 44: Mar-Apr 1986

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Evolving on half a wing (and a prayer?)

Just about everyone agrees that half a wing is of little use to an animal "straining" to develop the capability of flight. So, how did the marvelously crafted wings of birds, insects, and mammals evolve in infinitesimal steps? Biologists, including Darwin himself, have long puzzled over this. Stephen Jay Gould in a recent article explores a currently favored way of circumventing the negligible additional survival value of half a wing, or even 90% of a wing. This solution (?) maintains that protowings were not "intended" for flight at all but were developed initially as aerodynamic stabilizers, thermoregulatory systems, sexual attractors or other functions requiring large areas.

Gould describes the experiments of Kingsolver and Koehl in which protowings were modelled and tested for their thermoregulatory and flight values. Surprisingly, there was a sharp transition, as the size of the protowing increased, from good thermoregulation but poor flight capability to the reverse -- good flight capability and poor thermoregulation. In other words, a structure developed for one purpose, if enlarged, might be useful for something else!

(Gould, Stephen Jay; "Not Necessarily a Wing," Natural History, 94:14, October 1985. See also: Lewin, Roger, "How Does Half a Bird Fly?" Science, 230:530, 1985.)

Comment. The work of Kingsolver and Koehl, though doubtless of high quality, does not come to grips with the fact that a wing for flight is a highly sophisticated combination of skeleton, feathers, membrane, muscles, nervous system, control system, aerodynamic design, etc. -- most of which have nothing to do with thermoregulation. Are the flying crustaceans mentioned on page ** a failed evolutionary attempt at useful flight? And where did their feathery appendages come from? Somewhere we -- all of us -- are missing something!

From Science Frontiers #44, MAR-APR 1986. 1986-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
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  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987