As I have stated- you can only consider my or my wife's body parts as being part of nature if life originated via purely natural processes.
So what you're saying then, is that if life is the product of intelligent design, nature doesn't exist?
That's the pretty obvious extension of what you're proposing:
1) Any life that is intelligently designed is not natural.
2) All life is intelligently designed.
Therefore, you must obviously conclude that nature doesn't exist anywhere. What, then, is the word "nature" supposed to describe?