I think taking it as not to kill anything is... let's just say... based on an assumption about the definition or understanding of what "perfect" means. Is it absolute? Or is it relative? Me? I'm very logical. So I have to consider all the IF..THEN scenarios of an idea or belief.
Let us hypothetically say the bible is 100% truth and not the work of human hands and that it is the vehicle through which a creator spoke through. If I take this as granted what does it mean for life?
Well, it means, to me, that a contradiction is absolutely inevitable because if Adam and the animals were originally directed to be fruitful and multiply under this original "pre-sin" state of "perfection" then we might think this is good.
However, if this is the case then it is only a matter of time before the animals would be over populated, eating all the plant life. With the plant life gone the animals and humans would die.
So even if I ignore the natural life cycle of every biological cell and ignored that life has to have limits even down to the cellular level or else we would keep growing like gelatinous blobs... if I accept that limitation as "natural" but ignore the seemingly same type of mortality on the macro scale, every biological organism is built to run on energy which requires a fuel source. In other words, we are not magical beings that can breathe fire and fly without wings. We require energy.
And the fact is that our entire digestive system is based on consuming energy in the form of life. In fact, it has to be recently deceased otherwise it would be like eating poison.
The simplest forms of life, bacteria and other microorganisms, start eating and taking over, as if programmed to break down life to "return it to the dust from which it came". This very sentiment is included in the warning to Adam about eating the forbidden fruit, not just showing that he would be punished, but almost implying a forknowledge that his body would decay and be consumed/digested by microorganisms and perhaps other animal life prior to any written "change" into carnivorous behavior patterns. Of course the bible doesn't really say that none of the animal life ate other animals, but I'm willing to bet that the writer of Genesis knew exactly what happened when something died and that's why there really isn't an explanation or definition of life and death that is given to Adam.
But I think it is obvious that eventually procreating life would quickly reproduce faster than plant life could sustain. And then we would end up fighting for survival. And this is still true even if you consider that all the desert regions may have once been fertile. And even if you think you could keep up with planting, consider how much faster the land would lose its minerals and require fertilization and time to recover. Even if humans rotated crops the animals would not and you wouldn't be allowed to kill animals invading your land so everywhere they would be reproducing and competing with you for plant-based food.
Now if all animals and humans could graze on grass maybe this would be less of an issue but humans need nutrients that grass simply cannot provide just like how you can't live off salad.
Then there's water...
If you dramatically increase the animal population you also increase the amount of contamination; which would include sources of water which also draws insects and animals to drink as well as to lay eggs and "use the bathroom" in. And wow, can you imagine how many flies would exist if they literally never died? At what point would you be unable to walk around or see 5 feet in front of you due to the number of flies and other flying insects whose populations are regulated by birds and other insects? And what about ants and roaches?
I wouldn't want to live in that world. It would be like hell.
But let's say that after a certain length of time an animal just disappeared or once the numbers in a certain area were maxed out animals went barren or sterile. Are biological life forms immortal? What form of immortality are we talking about here? Does it include invulnerability? Can you still die from accidents? Disease? Are you immortal like the Highlander was immortal? Or self-repairing to the point of immortality? And then you have to consider that life may get pretty boring after a thousand years and a lot of people would be ready to end it. Especially since you'd practically be living inside a rated G movie.
And so when someone does "escape the immortal coil" who gets to then reproduce? Just the original man and his wife? Are humans, in this system, even allowed to have sex?
This is why I have to question the assumption that this was the original state of life on Earth. There is so much potential for things to go wrong that I'm not sure I could call it better than what we already have, as flawed as it may be. At least we get to choose how we live and when and if to kill.