Simplify the following text for a Grade 7 native English-speaking person.
Original: When the Daleks first appeared in The Daleks , they were presented as the descendants of the Dals , mutated after a brief nuclear war between the Dal and Thal races . However , in 1975 , Terry Nation revised the Daleks ' origins in Genesis of the Daleks , where the Dals were now called Kaleds ( of which Daleks is an anagram ) , and the Dalek design was attributed to one man , the crippled Kaled chief scientist Davros .
Simplified: Examples of such use can be observed in the serials The Power of the Daleks , The Evil of the Daleks and Planet of the Daleks .