It is clear from many discussions that there is a split between things people consider to be "natural" versus those that are the products of technology, or man-made.  Obviously no one would consider a computer to be natural, nor would anyone suggest that a tree is man-made.  These differences are intuitive.

However as our scientific knowledge has increased, and we are able to engage the fundamental mechanisms that were previously only within the domain of nature, this distinction is getting smaller.  With genetic manipulation, is the product man-made or still natural?  It obviously still has significantly natural components to it, and even its existence is still heavily dependent on its natural abilities for reproduction, and yet there's an element of "unnaturalness" about it.  It has been manipulated.

This creates a kind of cognitive dissonance in people where they seek to distinguish between something that occurs in nature, versus something that has been produced by man.  As a result, we get catch phrases like "Frankenfood", to indicate not only that something was artificially "made", but also invoking the monster with its message about tampering with nature.

Obviously many things that are natural are not beneficial; diseases, droughts, storms etc.  So, what is it about something being "natural" that is attractive while those things that are based on technology are not.

I'm going to suggest that one clear difference comes from a fundamental distrust of technology, in that it can go wrong in ways that nature rarely does.  In other words, there is a sense of "fairness" in the natural world that doesn't single out particular individuals.  A hurricane pummels everyone equally.  A flood puts everyone underwater.  There are no exceptions.

With technology, the implication is that there are exceptions.  Perfectly good technologies can go badly wrong because of human error.  Mistakes can occur.  In short, there's a sense that such problems are not "fair" and consequently there's more caution associated with such technologies.  Often this is accompanied by the knowledge that man-made disasters are frequently preventable.  They don't occur because we lack knowledge, they invariably occur because of mistakes, laziness, or incompetence.  As a result, these are perceived in a different light than "natural" events.

As an example, consider the general attitude towards accidents.  Suppose that an individual gets into an automobile accident and kills a pedestrian.  First we generally look to assign blame or fault.  However, if this can't be done, then we may be quite content to simply call it "bad luck" or an "accident".

In our example, let's imagine that the driver was intoxicated.  In general, we would no longer view this as an accident.  Blame can readily be assigned, and in many cases we would judge such an incident as being criminal, since the driver should be responsible for their actions in such a state.  

However, let's imagine that our driver attempted to stop their vehicle but the brakes failed.  Now, we might consider whether the car had been properly maintained, or we might blame the manufacturer for failing to produce a reliable car.  Again, we can assign blame.

In our third scenario, let's imagine that everyone is doing exactly as they should, but the pedestrian [at the most inopportune time] simply stumbles/trips and falls into the path of the car before any reasonable reaction to stop can occur.  In this case, we would likely label it an unfortunate circumstance and be content that no one was really at fault.  Similarly if the driver experienced something like a sudden heart attack, we would not assign blame for having struck a pedestrian.

All three scenarios will produce the same result, and yet our reaction to each one is decidedly different based on our interpretation of how we expect individuals to act and the responsibility we assign them.  

This is precisely what occurs when we consider the attitudinal differences between "natural" versus "man-made".

There is no one to blame in nature, so there's a kind of comfort in knowing that your survival is not subject to someone else's decision, actions, or mood on any particular day (1).

In cases like genetically modified (GM) foods, where genetic manipulation is producing different "natural" products, this feeling is exacerbated by the distrust that we have regarding blame for something that might go wrong.  In one way, regardless of the dangers present in nature, there is a sense that this is the environment in which we evolved and originated from.  Therefore, regardless of the hazards that may be present, it is something that we are specifically "built" to cope with.  

Therefore when technology produces uncertainty, it is not surprising that many people will simply revert back to their comfort zone, arguing that our natural environment [for good or bad] is the one we are most comfortable in dealing with and that anything artificial is introducing another layer of risk that we simply don't wish to deal with.

Unfortunately there's some element of truth to this view.  As an example, consider that medicine has clearly made phenomenal strides in treating disease and coupled with advances in surgery, have achieved results that are nothing short of miraculous.  Yet, one also has to consider that the likelihood of contracting a life-threatening infection has the highest probability of occurring in a hospital.  Nearly 100,000 people die every year in hospitals because of errors (2).  Again, the point is not to indict the medical profession, but to simply illustrate that man-made technologies will be viewed differently than the same events occurring naturally.  Ironically, people don't live in fear of the Bubonic plague, or even the influenza epidemic, however they will fear vaccines, or drugs.  Why?  Because there is little they can do about the former, and the latter has plenty of people to blame when it goes wrong, and unfortunately it does go wrong from time to time.

Invariably, much of these views come down to simple trust.  Raw milk is perceived to be better, because we know the cow can't deceive us.  The more people involved, the more tampering can occur, and then we have to assess how much we trust the people "in the middle".  The more people become familiar with the methods of production, then the more "trust" they have for those in production.  This is one reason why people tend to favor organic foods, is because there is a perception that the processes involved in producing the food are more transparent than other production methods.  Whether this is true or not isn't particularly relevant, since establishing trust, relates directly to the perception that these goods are "better for you"; i.e. more natural.

So regardless of how much scientific evidence is presented or denied by any particular side in this debate, the ultimate question is trust, and why it is either lost or gained.  People aren't fundamentally anti-scientific, and I suspect that most would clearly welcome a scientific perspective that they can trust.  However, decades of being manipulated by hype, advertisement, and simple salesmanship, has also convinced them of the importance of "caveat emptor".  

Much like bungee jumping ... you can tell me how safe it is with as much proof as you like, but you won't get me to jump off a bridge.
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(1) Consider that many people have a fundamental fear of flying simply because they are not in "control".  This is also not uncommon with many automobile drivers, that are distinctly uncomfortable being passengers.

(2) I will resist the temptation to discuss malpractice insurance.