In April 2000, the authors contacted more than 700 plural wives, asking them about their experience.
The origin of each system is slightly different; systems can result from trauma, as with DID, or without trauma.
Some systems remember the trauma which caused them, and others don’t.
Similarly, terminus ad quem ("limit to which") is the latest possible date of a non-punctual event (period, era, etc.), while terminus a quo ("limit from which") is the earliest.
For example, consider an archaeological find of a burial that contains coins dating to 1588, 1595, and others less securely dated to 1590–1625.
Some system members will have a better grasp of what caused the system’s genesis, and some alters may never know.