In science and philosophy, a just-so story is an untestable narrative explanation for a cultural practice, a biological trait, or behavior of humans or other animals.
A less pejorative term is a pourquoi story, which has been used to describe usually more mythological or otherwise traditional examples of this genre, aimed at children.
[1] However, the first widely acknowledged use of the phrase in the modern and pejorative sense seems to have originated in 1978 with Stephen Jay Gould, a prominent paleontologist and popular science writer.
"[7] In his book The Triumph of Sociobiology, John Alcock suggested that the term just-so story as applied to proposed evolved adaptations is "one of the most successful derogatory labels ever invented".
[8] In a response to Gould's criticism, John Tooby and Leda Cosmides argued that the "just-so" accusation is unsubstantiated as it claims evolutionary psychologists are only interested in facts already known, when in reality evolutionary psychology is interested in what can be predicted from already known information as a means of pursuing unknown avenues of research.
[9] Steve Stewart-Williams argues that all scientific hypotheses are just-so stories prior to being tested, yet the accusation is seldom levelled at other fields.
This method makes it generally impossible to engage in just-so storytelling because the hypothesis and predictions are made a priori, based on the theory.
Buss argues that Gould's failure to do this meant that his assertion that apparent adaptations were actually exaptations was itself nothing more than a just-so story.
[19] How the Snake Lost Its Legs: Curious Tales from the Frontier of Evo-Devo is a 2014 book on evolutionary developmental biology by Lewis I.