When the mutually agreeable arrangements of symbiotic relationships are in place for a long time, it can eventually 'institutionalize' itself by progressively blurring the clear distinction between the genetics of the symbionts. Ultimately, one organism may become part of the other. ex. Mitochondria, whose ancestry can be traced to the free swimming bacteria, once independent organisms before joining with other cell structures and becoming the power house of the animal cell.

Terrence McKenna