Why don't you tell me why you think ancient man needed to be "shielded" from details that wouldn't be erroneous.
For example, why did they need to be "shielded" from the (supposed) fact that the sun existed before plants on earth? Or, why did they need to be "shielded" from the fact that rain existed?
Ahh, but as a teacher, it is always more fun to let the students work out the details for themselves. Nevertheless, I will spoil it.
Why don't adults teach children about sex? It isn't because they are intellectually incapable of understanding it. The mechanics of sex, when you drill down to the basics, are surprisingly simple. And children even have the biological apparatus (half of it, anyway) to look at for themselves. So what would be the big deal about sex? Why is it that when a 6-year-old comes to us and asks where he came from, we reply with some piety like "from God" or "because mommy and daddy loved each other very much", or with nonsense like "the stork brought you", instead of simply pulling down pants and showing them how it works?
For starters, they are psychologically incapable of understanding sex. Not intellectually, since the basic mechanics are really quite simple. But you have to remember that before a certain age, boys think girls are slimy and icky and play with really dumb toys while girls, thinking themselves made of sugar and spice and everything nice, detest boys as stinky and disgusting and possibly the worst evil to walk the earth ever. Convince a boy that he would some day not just fall in love, and kiss, and marry, but also that he would actually want to lie down with and penetrate (in that order, hopefully) this icky alien from a different planet? Not going to happen. And try telling a girl that she would take this sort of thing lying down! Not going to work either -
even though it is absolutely true.
More importantly, they are incapable of handling the moral dimensions of sex and procreation. In fact, even many adults are still incapable of handling those moral dimensions. To teach a child about sex, within a Christian moral framework, would mean to teach him the whole works about sexuality from submission between sexes to chastity in marriage to why the world tells everyone to have sex to why we shouldn't accept any of that, and right on to the edge of controversy such as whether it is acceptable or not to use birth control (particularly post-zygotic ones, such as IUDs and abortions) and reproductive technologies. A child simply hasn't made enough moral decisions of depth to understand the magnitude of these moral decisions.
More importantly, when a child asks "where did I come from?", what does s/he really need? To know the mechanics of sex? Surely not. Of course a child being put together involves sex at some point, but sex or no sex, the child needs to know that as a human s/he is made in the image of God, and has been God-sent to his/her parents, who love the child to bits. The question of "where did I come from?" is not a question about mechanical origins, it is a question about spiritual significance - a way of determining not where did I come from but "who am I?" and "what do I mean?" Neither of these questions are answered by sex. They
are answered by the old patronizing cliches: you were created by God, and you are a product of mommy's and daddy's love. And that's all the answer the child needs to know even though sex is avoided with a ten-foot-long pole.
When the Israelites ask "Where did the world come from? Where did we come from?" they weren't asking about the
mechanics of how the world was created. God never goes into the detail of just
how He made the world. Genesis 1 narrates it on the level of "God said 'Let there be X.' And there was X. And God liked it.", which if you think about it, isn't too far at all from "Well, uhm, you're a product of mommy's and daddy's love" - no mention of intermediate stages, or processes, or even raw materials, or anything the ancients would have needed to understand the mechanics of creating a world.
And why? Firstly, because they would have been theologically incapable of understanding a God who works through naturalistic methods. Any Christian today who thanks God for the weather has to deal, whether consciously or not, with the tension between attributing good weather to a loving God and explaining it through meteorology - but such a tension only exists if meteorology is understood as a science, and the Israelites would not have been familiar with such a tension because meteorology wasn't a science for them. Not that there aren't fair-weather aphorisms by which people associate certain observations with certain weather phenomena, but the Israelites would never have understood that these things are repeatable and to some people apparently happen without supernatural intervention. Instead, the only way the Israelites could conceptualize God's presence and providence was via wrecking the laws of nature. In their books, anything they couldn't explain was an act of God, from lightning to sunrise to snow.
Would you expect God to give them the entire edifice of modern science just to make the point that God works through naturalistic means? Don't forget that a hundred and fifty years ago the very idea of the atom was still being debated. Would God have waited that long, waited for them to discover all of science (when during the time of Saul the Israelites still didn't know how to work metal properly), and then only revealed Himself and said "Look, this science you're doing here is all Mine"?
You might ask, "Why couldn't He have given them the science there and then?" Well, not just because they wouldn't have had any of the prerequisite
knowledge (not understanding, mind you, but sheer data accumulated over millenia), but because they wouldn't understand it theologically. They were surrounded by nations with entire pantheons of gods who squabbled it out with miracle after miracle. Would they have been ready for a God who, 99.99% of the time, doesn't even use miracles to provide for His creation? Or would they then have gravitated to the pagan pantheons? The Israelites were fickle enough even when God was working plenty of miracles for them; how do you think they would have taken it if He had revealed to them that almost nothing, even the very origins of the universe and of life, was a miracle? Even if it was
absolutely true? Would they still have understood what this God is and why He is worthy to be worshiped? They would have just abandoned Him for the Baals and Ashtoreths who openly promise miracles all the more.
But more importantly, as an answer to the question "where did we come from?", Genesis 1 answers: from God. And if you think about it, when we answer a child that s/he came "from God", we aren't saying that there was no sex - even though we would never go anywhere near sex in the description. We are saying that finding one's origin and identity in God is what's important, no matter the mechanics - whether you were conceived by your parents, or adopted, or picked off the street, or brought by the stork*, you came
from God. And in the same way, in Genesis 1, the mechanics and the details are irrelevant. The point of it is that everything came from God, evolution or not.
*Apparently, in Europe there is a positive correlation between stork arrivals on the mainland and births in hospitals. There must be something afoot. The whole idea that sex brings babies must be some kind of materialistic advertisement ploy.