Thanks so much. Well, scholarship on the John writings was very changed by the Dead Sea Scrolls. But it is curious just on its face that 1 John, apparently an intro to the Jesus teachings, has only one overt reference to any OT narrative—and that's to identify Abel's works as "righteous" and Cain's as "evil."
Your cues are so helpful- I hadn't even thought that "brother's keeper" might be Cain saying that Abel was not in his *herd*. It makes me wonder if he had slaughtered Abel in view of presenting an animal sacrifice. Reading awhile, I note a scholar suggesting that the term for' murder' in 1 John is really more 'sacrifice', and there's some feeling in early Christianity that Abel's death was Cain's "continuation of improper sacrifices to God…"
Cain's affront might shift to the special problem of human sacrifice.
The same scholar has a later paper about Abel's status after death as an ongoing figure of justice.