Creation of the Daleks

The creation of the Daleks occured during the Thousand Year War when the Kaled scientist Davros, who accelerated the mutations by treating living cells with chemicals to create what he believed to be the ultimate Kaled evolutionary form. These creatures were placed in tank-like travel machines whose design was based on Davros' own life-support chair. These Mark III Travel Machines, when coupled with the mutants, became the first Daleks.

The Doctor's appearance to try to prevent the creation of the Daleks in the first place, or at the very least lessen the damage they would do in future, led to the other Kaled scientists trying to shut down the Dalek project. To prevent this, Davros arranged for the Thals to be able to wipe out his own people. Afterwards, the Daleks were then sent to exterminate the Thals, but later turned on Davros and apparently killed him. Sealing them in the Kaled bunker, the Doctor still believed that he had only retarded their progress by about a thousand years or so, and that they would eventually return. (DW: Genesis of the Daleks)

Creation according to legend
Some time after the end of the Thal-Kaled war, the remaining Daleks, trapped in their city due to their reliance on static electricity for movement, believed that the war was a quick neutronic war, and that both sides of the war were horribly mutated from their original humanoid forms. However, the last part was later proven not to be the case, as the Thals were almost exactly like how they were before the war.


 * Whether this account refered to another war or whether it was the result of many years of accuate history being turned into legend is unlear, although it is apparently the latter.