Eating fish was genetically encoded in my cells. My ancestors were as coincidence would have it fisherwomen. It was those dam cells that made me eat the tuna. Genetics determining behavior is a good start. It's a popular theory that can be debated.
Debate is good.
It confuses people and will give me time to create defense two, the philosophical argument. Defense two goes like this. It's in the plan of creation. They know the score. Tuna fish don't mind.