The peacock’s tail is an artifact of a biased decision mechanism: description and simulation of declining threshold search

In sexual selection by female choice, declining threshold searching—a biased search strategy predicted by neurophysiology—can produce an open-ended preference for higher intensity displays. This can lead to the evolution of ever more intense displays until the upward pressure on display intensity is balanced by downward pressure from increasing male costs. The declining threshold search/decision mechanism requires no genetic diversity or survival advantage for offspring in males or females to be created or maintained. Here I describe the system and test its efficacy in a computer simulation, in which application of the declining threshold strategy induces spontaneous evolution of costly and intense male display values using only this mechanism. Applications of the mechanism include lekking (leks are simply display coalitions among kin to create a more intense signal than a single male can afford) and sympatric speciation.