We can't reproduce it... yet. You just don't have faith in mankind's creativity and ingenuity, don't you?
Not being able to reproduce it "yet" means we can't make it happen without engineering, which is what I state two lines later.
And if we have to be "creative" and have "ingenuity" wouldn't that STILL support that life HAS to be designed?
The only way science can even step up to the plate and take a true swing at the existance of something more than us is if they can present a case where life came from not only non-life, but also without planning.