Perhaps, mankind's first sin was killing a beast for food. The birds and fish just weren't good enough, had to go for those heart attack causing, cancerous beasts on the land.
According to some, this wasn't it for the creation thing. "Creator" said enough is enough and told Noah to build an ark and then... need I go on? Well my guess is this too would have to be a metaphor with a "do good" sort of theme.
After all the bible was written by men (not god/creator)
When you really get down to it, all laws are of religious decent. Murder is a capital crime, burglary will turn you into a felon, I don't know one parent that would encourage their children to lie, wait till your grown up to start having sex, and if you get married, you should really stick it out to the end. Now doesn't this sound sort of like the 10 commandments Moses received? Up date: commandment just down to me from Creator, #11- (he talks old time English) Thou shall not drive a motor vehicle when stoned on alcohol.
There was a time not that long ago, you would be hanged for taking a person's horse.
