We were speaking about the critical theory approach to Bible interpretation in another thread, and what it teaches about Adam and Eve and this story may be apropos here.
The story about Adam and Eve and the Garden of Eden is not an historical account of how sin can into the world. It is, instead, an explanation of why God has to call people--his own creation--back into union with their Creator. Again, mainstream theology as well as first-century Christian exegesis states that this is a story about "why,' and not about "how" as the Watchtower teaches.
The first 11 chapters of Genesis are allegories--parables, like Jesus of Nazareth used, to explain truths regarding humanity and its origins. Now it's not about origins, in the sense of giving a scientific or even popular superstitious view (even though, as critical Biblical theology points out, much superstition can be seen in the details offered, such as in Genesis 1 where the sun, moon, and stars are described as being stuck into a "firmament," meaning a dome that had an inner vault in which rain water could be stored). Like the parables Jesus used, these tales are purposely written with a style that readers of the past understood were allegory or religious stories with a moral to them. Instead of marking the writings with numbers of the Dewy decimal system or words such as "Fable," the way we do with modern books, all ancient Mesopotamian writings of the time used narrative devices or indicators to make the stories impossible to be confused with literal reports (such as telling one creation story in Genesis 1 and then suddenly telling a conflicting one right afterwards; it's not a mistake, but a common earmark that says: The details are not where the truth lies, so look for a moral).
The following stories in Genesis are more historical with less allegory, but mythos nonetheless (again, not to be confused with the vernacular use of "myth" meaning "falsehood;" the literary meaning of "myth" is here meant, an "origin" story, usually wrapped in a religious lesson or view of the meaning behind historical events). The story centers around Abraham, then Moses (as Genesis is one book with the four that follow it in the Tanakh, a combination known as simply as Torah, "Law").
The critical approach teaches that the main thrust behind this book is not what the Adam and Eve story tells us about history but what that story has to do with why God called Abraham to follow him, and why later God sent Moses to call Abraham's children to freedom. The reason? Simple: Humans have a tendency to throw God out of the picture, even when it is evident that to do so is to their detriment.
The Adam and Eve story is not a story of how sin came about, but that we are subject to concupiscence, a desire to do things based on our limited experience and even deifying that experience, often comparing it to that of God's knowledge and wisdom, or supplanting the need for it.
In the story, Adam and Eve lose paradise because of this. But we never really are told exactly what they did, besides eating fruit, that introduced this concupiscence in the first place. As the apostle Paul later stated in one his letters, eating doesn't cause a person to get closer or further from God. Only doing something with the full knowledge that it will displease God and even cause harm to another, even their neighbor's conscience, is considered sinful when Paul discusses food. (Romans 14) Therefore it is would mean even throwing away the logic of an apostle to teach that Adam and Eve's eating of fruit was literal, since there is no power in food itself, for good or evil.
So the question as to when Adam has sexual intercourse with Eve is moot. The story is merely saying that Adam and Eve passed on this condition we seem to be unable to conquer on our own, and that God intervened by befriending Abraham and then freeing them through Moses because people cannot follow God's law if left to themselves, even if it were offered to them via theophany like a burning mountain, a loud horn, and the thundering voice of God himself.
An interesting note: Both Adam and Eve and the newly freed nation of Israel get to hear God's voice, and then both are said to replace God, one by throwing him aside for their own wisdom and the other for making God into something God is not.
Of course, I'm not saying this is the only accepted understanding or there aren't other details offered by critical theory used in Biblical study. Neither am I trying to insult those who are atheists or agnostic and claim another set of convictions. I am merely stating that the Watchtower view is nothing like that held by the majority of Jews, Orthodox, Catholics, and Protestant Christians outside of the ignorance offered by the Governing Body as "food at the proper time."
The food of the Governing Body is like a stale candy bar compared to what "Christendom" feasts upon via the use of critical analysis.