Explaining Evolutionary Adaptations and Side Effects The Spandrels of San Marco-0
Explaining Evolutionary Adaptations and Side Effects: The Spandrel
An architectural spandrel
A spandrel is a useful characteristic that did not orginally come about for their current use. Rather, a spandrel is a by-product of the evolution of some other characteristic.
Background[]
In the basillica St. Mark's in Venice, there are beautifully decorated triangular spaces in the spot where the archways that support the roof meet. This is a great use of the space, but the intention of the space was not designed for that purpose. The lesson here is, when a trait that has a good function, don't just assume the trait was desinged for that function. The trait may be a by-product of the evolution of another characteristic. A spandrel, as the space between two archways is called, is also a term used in evolution. Stephen J. Gould is an evoluntionist who has written about evolutionary spandrels. In Gould and Lewontin's paper "The Spandrels of San Marcos and the Panglossian paradigm: a critique of the adaptationist programme", spandrels were used as an example to explain why adaptationists were wrong (Gould & Lewontin, 1979). (Adaptationists believe every trait came about as the result of natural selection).
Gould, S. J., & Lewontin, R. C. (1979). The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London. Series B. Biological Sciences, 205(1161), 581-598.
Examples[]
Some examples of spandrels include:
The red color of red blood cells (they contain hemoglobin for transporting oxygen and carbon dioxide)
The pseudo-penis of hyenas (now considered an exaptation)
The by-products of the large human brain: religion, reading, writing, fine arts, etc. (Gould, 1991)