Theory:Timeline - Daleks

The Dalek timeline theory speculates that the Daleks have two timelines. The first, Davros really did die when exterminated by the Daleks after their creation. It first appeared in print in The Discontinuity Guide.

Summary
In one timeline, Davros created the Daleks, who killed him. This timeline encompasses all the Dalek stories from their debut, The Daleks. In this timeline, the Daleks develop full time travel, though they destroy each other (possibly) in The Evil of the Daleks, which the Second Doctor regarded as their "final end".

In the second timeline, created by the Doctor's intervention in Genesis of the Daleks, Davros actually lives. The Daleks revive hiim in Destiny of the Daleks and, later, his survival provokes the Imperial-Renegade Dalek Civil War, which weakened the Daleks so that they never develop full time travel and the Seventh Doctor destroys Skaro at the end of Remembrance of the Daleks.

Therefore, while Davros existed in both timelines, Dalek stories set prior to Genesis of the Daleks, and those set after, take place in different continuities.

In the Real World, Davros never appeared on-screen because up until Genesis of the Daleks, Terry Nation had not invented the character and the Daleks had had several accounts given of their creation which differed from each other in various degrees.

Canonical support or denial
This theory pre-dates the recent television revival of Doctor Who, though, which does not feature the Daleks as having the kind of internal dissent as in earlier stories and in which the Daleks have full time travel capacity.)

John Peel's "revisionist" War of the Daleks did come at the theory from a slight angle, however, and suggested that, in reality, the Daleks had put into motion a hoax which involved pretending to go to war with the Movellans and staging a fake Imperial-Renegade civil war, which would mean Davros had a much less disruptive influence over the Daleks than shown on screen. The new series of Doctor Who has not, to date, touched upon the theory directly, though in continuity terms, the Time Lords attempt to alter Dalek history does feature into the backstory of the Last Great Time War.