In general use, evolution in this context refers to theories which identify, and then connect, the discrete steps involved in the process of change from original idea, to its stable form, for example, the first telephone used a different process for converting sound into electricity than the first commercial phone, this step would be part of the telephone's evolution.
The evolution of an idea or concepts should be further analyzed. Changes occur due to specifiable types of stimulus or input during the analytical process; these changes occur along specifiable dementions.
Types of input may include outside information supplied by another thinker external to one's mind, or the realization of a flaw on one's own due to an inherent contradiction or paradox. Changes can also occur seemingly spontaneously, during the evolution of an idea one can receive "inspiration" from various sources that are often seemingly unspecifiable.
Changes can happen to the overall way an idea is structured. One may realize that a simple rearrangement can shed light that seems to fill an invisible void. Changes can occur to specific elements of the idea, some specific component of a conceptual construct can sometimes be altered to be more specific or more broad, or even completely different without disturbing the overall structure, but changing the understanding that the pattern conveys in a beneficial or detrimental way.