XLord007 wrote:but the latter sounds like a manifestation of a psychological problem.
Considering that sex is on even terms with eating and voiding in the sense that cognition is not a requirement, I can offer something to your point of view.
Keep in mind that I'm not familiar with every related psychological problem, but here are a few:
Anorexia - extreme caloric reduction
Bulimia - intense caloric increase
Paruresis - fear of urination in certain places or in the presence of humans
Parcopresis - ability to defecate in certain places only
What those 4 basic disorders have in common is that they negatively affect one's ability to carry out requirements for continuation of existence, which are eating and voiding. So, if something negatively affects sex, it is probably also a psychological problem. For an individual, sex is not as important as eating and voiding, but for a species, sex is the most important thing. I would argue that psychological problems related to sex are of minimal concern unless the birth rate declines sharply. In fact, psychological problems related to eating and voiding are also of minimal concern, since they affect so few people. It's not until a psychological problem becomes a full fledged disease that we have to worry. Imagine, for instance, if some microorganism caused anorexia in 100% of people it infected. I'm not saying this microorganism affects appetite. No, I'm saying it affects the brain, which in turn controls appetite. Luckily, no such creature exists, but it could. I seriously doubt that such a creature could occur naturally, so if some psychological problem starts affecting 100% of us, we can assume we are being attacked.
I didn't mention the sharp difference psychological and somatological problems, so I'm doing this edit. Anorexia and the like occur entirely within the mind. There is actually some damage to the brain, which, in turn, harms the body. My point is that a psychological problem will always have a somatological effect, but it is easy to confuse the two. For instance, those with paruresis are often mistaken for having dysfunctional bladders, but the bladder works just fine; the part of the brain that controls the bladder is damaged. I don't know the full extent of psychological problems, but I imagine that each organ within the body can be coaxed into dysfunction merely by damaging the brain. Even further, the damage to the brain is not somatological, it is also psychological. So, there is physically NOTHING to repair! So where is the problem? This is why psychological problems are so fascinating to me.