While some academics contrive spandrels or non-adaptive byproducts to account for human art and religion, actual empirical support in the scientific literature for non-adaptive byproducts, behavioral or otherwise, is virtually non-existent. The few papers that tackle this question tend to criticize the concept. In Adaptations, Exaptations, and Spandrels, lead author David Buss (1998) says, "Hypotheses about functionless by-products must meet rigorous scientific standards." (p. 542) He concludes, "We could not find a single example of an empirical discovery made about humans as a result of using the concepts of exaptations or spandrels." (p. 545)
Several proposed examples of possible phenotypic non-adaptive byproducts are male nipples, the navel, and the female hyena's gentalia, which is very male-like. However, there is no analysis in the peer-reviewed literature that meets the scientific criteria for these to be accepted as legitimate non-adaptive byproducts, and there are good reasons why they are not non-adaptive byproducts. The non-adaptive byproduct or spandrel is much like the way in which religion solves the mysteries of life: it is inappropriately utilized to construct answers in the absence of better explanations.