It's also interesting that Davros is referred to as a Kaled despite his radically different appearance. The fact that he is confined to a chair and has the use of only one arm suggests that he was involved in some king of accident. Hopefully more information will be given about him in future serials since I know he did not actually die at the end of Genesis.
His later TV appearances don't really fill in on his earlier history (the closest is that there was reportedly a flashback scene to his early life scripted, but not shot, for the most recent one), but there are plenty semi-canonical takes on it.
In particular, there's a four part CD series, I Davros, covering his childhood and early life, with Peter Miles reprising his Genesis role as Nyder. But personally I prefer the version that was printed (in wildly inconsistent versions) in Annuals and other tie-in books during the late '70s, before the character had even reappeared on TV, because there's a tragic simplicity to it. It runs something like this...
Davros was born on the day the war began.
He never knew his father, who was killed leading an attack on a Thal base when Davros was still a baby. Davros's earliest memory is being presented with the award for valour that was posthumously awarded to his father.
Davros's mother was killed by a Thal air-raid when he was six. (which is not the way I Davros tells it, by the way).
By this time, Davros has one ambition: once he's old enough, he wants to be a soldier and fight the Thals (after all, they killed his parents).But his natural genius has already been spotted, and he's hothoused through the school system and college.
By the time he's 12, Davros is already a genius, a key member of an elite unit developing weapons to use against the Thals. But he still sees this only as his way of fighting until he's old enough to be a proper soldier: he intends to join up on his 16th birthday.
A few days before that, however, he's crippled by a massive explosion. Reports as to the cause vary... a lab accident. A random hit on his lab by a Thal shell. Thal sabotage designed to kill the Kaled boy genius. Kaled sabotage to ensure Davros remained in the lab, rather than getting himself sent to the front and killed with a week. Could be any of them... but the end result is the same: Davros is horrifically hurt, but saved by intensive life support. Eventually he builds a mobile life support chair for himself. This keeps him alive for so long that as the war drags on for centuries, generations of Kaleds grow up in awe of Davros, the man who will not allow himself to die until the war is won...