THE GROUND WAS CURSED.
"in the sweat of your brow shall ye cultivate it."
In other words, a vegetarian diet was very HARD work and unreliable as a source of food.
Millet, rice and wheat were not yet domesticated.
Adam and Eve were thrown out of Eden BEFORE they had even planned to plant next years crops.
They knew animals were killed to clothe them. Why not kill animals to eat until the first meagre(cursed) crops grew?
We need to remember that the Canaanites worshipped AGRICULTURAL fertility gods who were offered constant VEGETABLE sacrifices. So Cain offering vegetables puts him in the camp of the Baalworshippers and the Sodomites. Remember Lot chose the land of Sodom for its superior vegetable sustenance.
No the jews were sheepherders, so Abel is portrayed in a good light.
If they had bred pigs he would have sacrificed a pig.
Revelation 7 would say the Great Crowd have washed their robes in the blood of the Pig, and it would be a pig standing on mount Zion.
"Behold the Pig of God that taketh away the sins of the world."
if lambs were unclean then jehovah would be insulted as the scripture says by one "offering up the blood of a lamb!"
It is all anti gentile propaganda.
HB