well, this topic came up in my bio class, and my friend Max and I started to talk about it. We were first learning about blood types in class (nothing stikingly new) and it occured to me that she never told us why we have blood types. So I asked her and she simply said, "Well, why do we have eye color?" So it got me to thinking about how mutations occur without a beneficial reason nor do they come from need. As a matter of fact, most mutations either do nothing or are harmful. We did not mutate to have opposable thumbs so that we could pick up things, we had the mutation and then we discovered a purpose for this mutation. Then, through selective breeding, our species came to have opposable thumbs. The mutations that occured creating an opposable gave the mutating being an advantage over the non-mutated, thus the mutated beings survived easier that the non-mutated. This is not an accurate example, because I do not know the specific gene regulating thumbs so I do not know about this mutation, but it does portray my thoughts. Basically, if there was a need, and one such mutation fulfilled this need, this mutation would become widespread throughout the entire species.
So, in the case of mutations, existence precedes essence. And this is so with all natural living things, and with the universe. Throughout the universe are scatterd things called "nebulae" which are typically comprised of gas and particles. Usually, thanks to gravity, they will eventually form into galaxies made up of stars, planets, moons and the like. So, you see, the existence of gas and particles gives way to galaxies, which may have more order and purpose than free floating matter. This can definitely apply to all natural living things. Drawing from the idea of mutation, one can see how species evolve first, and then can fit into the food chain or the environment and can serve a purpose on our planet.
This may also apply to the life of a human being. Throughout history, philosophers have been comteplating the meaning of life, and all people the meaning of their own individual lives. Humans are born, arguably, without purpose. Through natural reproduction, babies are born and as they get older, they will begin to question life: "Why do I have to live?" "Will I really make a difference in the grand scheme of things?" If I simply let go of life, will it make a difference?" "I'm not really enjoying life anyway." These are the questions that go through the mind of a typical adolescent. However, as these adolescents grow older, they get jobs, they fit into society, they feel like they have a purpose, and eventually, possibly to make themselves feel even more worthy, they have more children. This is the general progression of life, and shows how existence precedes essence.
On the other hand, there are things that exist in life that do not follow this pattern. We have normally labeled them as "unnatural" things. We, as humans, have a need to fulfill. We find resources, we create something, and this need is fulfilled. This is not the general progression of natural things. This is that of unnatural things, such as tools and machines. However, this line between "natural" and "unnatural" is very indistinct. Going by the law that "all things in which their essence precedes their existence are unnatural", we would have to conclude that many things we view to be natural aren't truly natural. First of all, all government must be unnatural. We saw that humans have many faults, and to prevent these faults from destroying the lives of others, we set up laws and government to keep us in check. We also created government to simply make us, as a human race, stronger. However, government was not established before we became a species; our intelligence allowed government to be formed.
Also, all of our tools and creations, no matter how primitive, would have to be unnatural following this law. For example, spears would have to be unnatural. Though they may come from natural products, wood and stone, the product of the human mind that is a spear would have to be unnatural, because we thought of a spear, and then it came into existence. Also, "all-natural" juice is also incorrect. Though your everyday juicy juice may be made from natural ingredients, the combination with the addtion of various flavors, not to mention the packaging and marketing, make it an unnatural object based on this law. But most people would disagree with these examples. After all, it isn't only humans who use resources to make tools. Birds make their nests out of sticks and ants make their homes out of the dirt. So just what is natural?
What about genetically modified animals? As one example, we have made genetically modified goats that can produce thread strong enough to hold a car. Would these goats be natural beings? They are certainly organic and living, but are they natural? If not, does that make EVERY creation unnatural? How about test-tube babies? They are not born through natural child birth, however would you deny that any child born this way is natural? Is it even "moral" to say so?
However, it may be morality that blurs the lines of the natural and the unnatural. "Unnatural" has an unfavorable connotation to most people. So, if we find something to be useful, and we agree that it's benefits outweigh its detriments, thus making it "moral" in our terms, we can view it to be natural if we choose. Because, if it wasn't natural, than it would make it less moral. And, if something isn't moral, than it is unacceptable. However, morality is in the eye of the beholder.