Radar, I wonder if one of your television watching extraterrestrials could answer a question. Some intergalactic acquaintances were just asking how things done by man escape being referred to as natural. Mankind, in the flesh at least, for all his hubris still has a dust to dust existence thereby falling short of divinity. Surely other species such as spiders producing silk with tensile strength comparable to high-grade steel but with only a fifth of the density or salamanders with their DIY hip replacement technology can be considered equal contenders for the supernatural award. We have a financial system...or maybe that is the other way around - poor example. So why don't man's products and by-products qualify as natural?
Anyway I must finish my book; Igloos for Dummies.
JWW Brennan,
Oh yes, they were very specific on some of these points. All of the feats that mankind (as we refer to ourselves) does must be natural, as we are natural. However, we do not have a "dust-to-dust" legacy. This is a misinformed notion based upon what what we think or percieve that we know and understand. There is much more to "us" than we see at face value. We were actually planted here (or transplanted here if you will) for them to learn from our existence in this physical form. What we learn here, in this form, is what teaches them what they do not understand. We are like the egg that becomes a tadpole and evolves to grow legs and lose gills to breath air, then leaves the sea to crawl upon the land and then... dies in order to change form once again into something greater... Same as the butterfly, from egg to caterpillar to pupa to butterfly and then to something else that we do not see.
Nothing that we are or that we produce or create was never created before. It has always existed, we have always existed, everything has always existed, just possibly in slightly different form. Simply because we manage to build a skyscraper does not mean that we are any more or less unique than the termite that builds a mound on the plains of Africa. With one exception... We do NOT fully return to dust.
To address your question in conclusion here, there is nothing "earthly" that is NOT natural and that will ever be unnatural, except that which is NOT of the
"THIS" physical world already... and that
"SOMETHING" does exist.
RADAR
Good luck to them because I have a hard time figuring out what is going on on our own planet watching this stuff. 
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