I did not understand that.
I am not quite with you here.I don't know that without a conscience protecting the weak has any merit at all in a natural society, it doesn't in the wild.
I am not sure when or where we talking about here.Until recently our societies left mentally ill to die, mentally retarded or handicapped to die and wasn't so great to sick and old. Children were also considered the property of the males and could be killed if the head male felt like it without having to explain it. Women also.
I think it is useful to see this in terms of human history, which is after all some couple of million years old.Either conscience is developing as we develop or who we have conscience for or about have grown as our species have grown.
As Leo9 said, there is evidence that the tribes took care of their sick and young, and that, to me, is simply common sense in terms of survival for all.