My son, who is eight and a half years old, has begun asking about sex more frequently in recent months. His questions are less about the reproductive aspect of human sexuality (which he understands, because it is explained in verbal and visual detail in many children's books and documentary films, both on human reproduction and animal life) and more about the basic procedure of human intercourse as well as about what adults would call lust and eroticism.
Being familiar with his own penis and the flaccid penis of his father as well as the outward form of female genitalia, my son seems to find it hard to imagine that a penis can be inserted in a vagina and what needs to be done to produce those enigmatic spermiums that he as yet has never seen and probably cannot conceive of ejaculating from his own member.
He also does not yet have any romantic, much less sexual, feelings about girls (or boys), and the only difference he sees between the genders are differences in the media they prefer. Otherwise girls are just as much fun to play with, and he does not quite understand why any person might want to kiss or caress someone except for familial affection.
In other words, he is still (sexually) an "innocent" child, but he recognizes signs of romantic and sexual activity in the adults, teens and other children around him (and in the media), and he is curious about what it all means (and, possibly, what is coming up for him).
I have begun to go through the books that are advertised as explaining the topic of human sexuality to children, but I have found them to almost completely omit the reproductive act itself as well as everything that has to do with sexual lust. They do mention love (albeit usually between married parents), but they do not help a child prepare for a teens feelings of horniness. They do explain (often in boring detail) the development of the fetus and the hormones of the female cycle, but they do not even mention wet dreams or intercourse.
When my son asks me, I try to answer as truthfully as possible, but I often find it hard to explain some aspects without visual reference.
When a child asks you about how something is done or what a certain thing looks like, you will find it easiest to give a comprehensive answer by showing him the activity yourself or a movie that shows it. For example, when you try to teach your child to swim, you wouldn't expect him or her to understand what you are talking about without ever having seen another person in the water. In fact you will perform the movements and ask your child to mimick your behavior.
For that reason, I have wondered wether or not my son might find it helpful, if I allowed him to view some (carefully preselected) pornographic images or (preferably) a pornographic movie. There are a few videos and photos on the web that to me show what I think of as tender, loving sex and that include only what I perceive to be normal, healthy sexual behavior.
But apart from worrying about my son telling his friends, and them telling their parents, I also wonder if this (one time!) exposure would either shock him or influence his own sexual development unfavourably. I think, neither, but what do you think? Or what alternative do you recommend?
Some general comments to the comments and answers:
I have seen some pornographic movies that portray realistic, loving sex. I don't want to link it, but please believe me, that it exists.
The book Show me! by Will McBride features explicit photographs of people (including children) being sexually active. It was published in Germany (where I live), won prices (incuding prices by church organisations) and withstood several court cases here and in the US. You can find some of the images through Google. I would have bought the book, but it is quite expensive today.
I own a teen sex ed book, Make Love, also published in Germany, which features explicit photographs of adults having sex. It has been highly praised in the media here, and is legally available in book stores. Some of the images can be seen in this review in censored versions.
Specific comments under the respective answers.