Yes amadeus thats why I was putting it out there that Cain could have offered God fruit from the wrong tree. I know it says fruit of the ground, I dont know if it means fruit that was fallen on the ground...or a different kind of fruit that wasnt from the tree. Cain was a tiller of the ground but nothing indicates what kind of crops he was growing. It could have been figs....adam and eve hid behind fig leaves.Does it not appear at times that people are partaking repeatedly of that wrong tree? It started with one simple rule which was simply disobeyed. Man has grown from there in his own ways including a tremendous knowledge through scientific study and such. Look at where the world of men [outside of believers, but including them as well in a measure] is today. We started twisting God's simple and perfect way after that first sin. For example as consider what Jesus said here:
"And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,
And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh?
Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder." Matt 19:4-6
Yet when we read the OT we see where polygamy was an apparently accepted way for even some of the so called patriarchs and even David the man after God's own heart.
How could David be one flesh with all of his several wives? What I see is that man had moved so far away from the simple perfect of Eden prior to that first disobedience, that God had to continuously guide people one step at the time to His right Way. The problem was that people kept on eating from that wrong tree. The possibility of really reversing this for most people did not exist until Jesus made a Way for it to happen.
Contrast that with Abels offering. His firstborn with the fat...Jesus was the first born and anointed one. Theres a parallel there.
All through the OT people just did what was right in their own eyes only the faithful truly listened to God and discerned what His will was. We dont have any recorded conversation between Abel and God, but why was he keeping sheep? Well it was probably for clothes they needed. Wool.
I mean Abel could have kept any other animal, as other animals can be used for clothing but its significant he kept sheep.