http://en.wikipedia.org/wiki/Just-so_story - also called the ''ad hoc fallacy'' - is a term used in academic anthropology, biological sciences, social sciences, and philosophy. It describes an unverifiable and unfalsifiable narrative explanation for a cultural practice or a biological trait or behavior of humans or other animals. The narrative need not contain rigorous arguments, facts, or experimental results, so long as it is very entertaining, and plausible within its limited & fanciful world. A turtle, for example, can "evolve" into an armadillo by asking a friendly hedgehog to unlace its back plates, and teach it to curl up.

A JSS is perfectly fine if you declare it's one up front. For example, "old men like young healthy women because they are evolutionarily more likely to bear healthy offspring". Now this sounds charming, and explains many of our romantic (and tawdry) stories, and for all intents and purposes it might be true. However, it is neither a scientific hypothesis nor rigorous in terms of reproducible results.

A JSS is also completely valid as a WorkingTheory. When tracking the elusive HyperBug, a story about its life cycle, even if ridiculously false, will form a good checklist of ways to attack the code. Running the checklist will replace the pretend theory with hard evidence.

For example, a JSS regarding the many varieties of dog, none wolf-like, appeared in many textbooks: "Wolf packs drove out the pups that looked different, and humans adopted them." The truth turned out different. Humans adopted docile dogs who followed nomadic humans & picked at their leftover middens, and humans bred them for further docility. Many mammals, with less aggressive hormones in their system, lose their strict morphs. Minks, guinea pigs, fancy rats, cats, sheep - all show wider variation than their more aggressive ancestors.

JSS stories have filled many popular books, appealing to the "cult of scientism" (http://www.michaelshermer.com/2002/06/shamans-of-scientism/). They use scientific-sounding arguments to make the reader feel like a genius. Examples include ''TheOriginOfConsciousnessInTheBreakdownOfTheBicameralMind'', ''FutureShock'', or ''TheSelfishGene''. They spin modern fables around the doctrines (and dogmas) of evolution, the way the morality plays of yesteryear spun fables around ... certain other dogmas and teachings.

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"Said Leopard to Baviaan (and it was a very hot day), 'Where has all the game gone?'

"And Baviaan winked. He knew.

"Said the Ethiopian to Baviaan, 'Can you tell me the present habitat of the aboriginal Fauna?' (That meant just the same thing, but the Ethiopian always used ''looong'' words. He was a grown-up.)"

--RudyardKipling