Where is the Line Drawn Between Natural and Artifical?

In class we discussed sex-selection and on some of the posters the idea of natural versus artificial was written down.  Many people consider IVF and sex-selection and unnatural process that tampers with the biological equilibrium.  IVF pregnancies are considered “artificial”.  I am curious when the line between natural and artificial was initially drawn.  Since everything that humans make, comes from nature in the first place, when does an object or an action pass over from natural to unnatural or artificial? How were these distinctions created and why do they have such an enormous impact on the ethical decisions our society makes? 

I believe that part of the reason this happens is because with new technologies and modern science, humans feel a dominance over nature.  Nature is something that people are a part of, but something that people feel they like they own.  The more detached from technology, the more natural and the more complex and creative the object, the more artificial it becomes. 

An example of this is the opposition to homosexuality.  Many people are against homosexuality for religious beliefs, as well as the belief that it disrupts the natural order of the world.  The disruption of the natural world is considered wrong and equilibrium is right.  People also have negative feelings about surrogacy because some believe that it is not the way a woman is supposed to reproduce and that it is “unnatural” for a woman to carry a baby for nine months that is not genetically hers. 

On the other hand, too much nature is also looked down upon.  An example of this is in the case of European colonialism in Africa.   The Europeans came into Africa looking down a population that they considered too primitive and animalistic.  They associated African people with animals because the Europeans believed that the people they were trying to “civilize” were too close to nature.  In the case of colonialism, too much nature was considered problematic and below the standard of human living.

Why does this equilibrium exist and why do so many people in power get to control the limits upon what is too natural and too unnatural?