Cosmas Indicopleustes

If it is true that before the Flood they did not eat flesh, why is it then written: Abel was a keeper of sheep, and brought of the firstlings of his flock and of the fat thereof? If they did not eat flesh, why did they take upon them the care of sheep? And why did Abel, when he brought a lamb for sacrifice, not slay it? Now, one who so enquires, will be truly answered that, in making the oblation, he presented the holocausts alive; for one of the editions shows this, saying: Over Cain and over his sacrifice he did not apply fire, so that it is evident that the offerings were consumed with divine fire. They provided themselves with a flock to procure for themselves milk and wool. Another objection: If they did not eat flesh, how came it into their head to select the fat for the sacrifice to God? Answer—Because when anything is to be burned in the fire, fat is more readily set ablaze