You've selected an element of life [procreation], and declared it to be the purpose of it all. Humans have the ability to create life. Humans have the ability to end life. I wouldn't say that the purpose of life is death simply because I have the ability to kill. I would recognize this as an ability that I have, and leave it at that. You don't know what the actual purpose of life is, in the same way that you don't know what happens after life, but people have issues with ambiguity. You don't desire to procreate out of some cosmic sense of responsibility. You just have that ability. I feel that your true desire is to rationalize your own existence, and declaring procreation to be natures only purpose satisfies that desire.