Their creation is the feat of the kaled scientist Davros, although the initial concept was presented to him by his assistant Shan; from whom he stole the idea, and adapted it into what would become the Daleks. They were developed toward the end of the One thousand years Wars on Skaro and ended it by eliminating most of the two warring parties, the Thals and the Kaleds. They then became stranded in their city for a while, but somehow survived and, led by the Dalek Emperor and the Dalek Council, forged an interstellar and later intergalactic Empire. After clashing several times with Timelords agents, they began working on a time travel technology of their own and came several time to Earth which was one of their first battleground with their soon-to-became nemesis, the Timelords, first by developing time corridor technology, then by building time travel machines based on temporal shift, efficient but not as much as the Timelords' Tardis.
Travelling through time themselves and being at war with the Time lords, the Daleks have seen their history and development rewritten several times already, a process which is still on the way.Source: Doctor Who universe, (TV: Asylum of the Daleks), (TV: Resurrection of the Daleks) (TV: Genesis of the Daleks), (TV: The Daleks), (WC: Captain Jack's Monster Files) (TV: Dalek) (TV:The Dalek Invasion of Earth, The Parting of the Ways), (TV: Revelation of the Daleks, The Parting of the Ways, Asylum of the Daleks), (AUDIO: Davros) (TV: Doomsday, Daleks in Manhattan)
(TV: The Daleks' Master Plan), (TV: The Chase),