In the archives of the Istanbul archaeological museum there is a cracked tablet. Written in about 1,250 BC it is the office copy of negotiations carried out in the late Bronze Age. A princess from Amurru (in central Turkey) has been given in marriage to the King of Ugarit. But when the young girl gets to the court she behaves badly - the implication is that she has an affair - and the two states come to the brink of war. The negotiators do their job well and the situation is diffused; had it not been, the history of the Near East, of Persia, Turkey and Greece could have been very different - and all because of a small sexual scandal, an immature girl's peccadillo.
This historical fact was recorded at a time when much of Greece and the whole of the rest of Europe was still lingering in pre-history. Yet it has immediate resonance today. That affair took place close on 3,500 years ago: the curious irony is that rather than being studied because of its great age, it is ignored. The majority of children drop antiquity as a topic after Year 6. The overwhelming bulk of history taught in secondaries focuses on the modern world. Most A-level history students study only the very recent past. The implication is that human acts have most relevance when they occupy the same time frame as our own. That is sheer lunacy.
Take a dreadful recent example; the latest Bali bombings. To understand these we do not just need to look at the reaction to Iraq or 911. The group responsible for those bombs, Jemaah Islamiah, was built on Muslim resistance to Dutch and Japanese occupation of Indonesia in the 1940s. And to understand the origins of East-West conflict we need to look back much, much further; beyond the world wars, crusades, birth of Islam, back perhaps, as far as the Bronze Age. This antagonism was a live issue, much debated, at least as early as the fifth century BC.
Poor old Helen of Troy was blamed. Isocrates, in his Encomium on Helen, said "because of her Europe set up a trophy of victory over Asia". Teaching the story of East-West terrorism with a 21st-century cut-off is worse than irresponsible. It does not clarify our place in history, but obfuscate it.
Of course it is unrealistic to know everything about all things. But the roots of our lives run deep. By tracing them back we will find lessons from the dead to arm the living.
One problem with selective history teaching is that the later you mark your starting point, the more deterministic history becomes. Victorian specialists claim the birth of the middle classes for their period, 18th-century experts for theirs. A medievalist will tell you it goes back to the after-effects of the Black Death. Without offering a broad sweep of history it is impossible to understand its eddies, flows and cycles.
And by cutting out the histories of the ancient and early medieval worlds, we deny students the opportunity to study societies before democracy was a twinkle in a demagogue's eye, a time when women were on top - at least in matters religious, when the known world was dominated by teenagers (we imagine the heroes of the Iliad to be grizzled warriors - skeletal evidence indicates most would have been active on the battlefield in their teens and early 20s - dead by the time they were 28).
I studied classics when it was deeply unfashionable so to do. There were only three of us learning Greek, everyone thought we were potty - "do something more glamorous" I remember one teacher shouting at a careers meeting. But now TV executives and publishers are vigorously shoving media studies CVs into the bin and putting to the top of the pile those who have read ancient history or the classics. A study of the past encourages the student to analyse a range of data, to look beyond the obvious. And exploring the distant past - where men and women were living without the accretions of time and experience - brings us all closer to the essence of what it is to be human.
Focusing predominantly on 20th-century history is like trying to understand the human body only by observing the skin. History is not a single organ, or even a row of organs on a surgeon's slab, it is a corpus. And if government advisers continue to degrade the distant past, to determine what is and isn't "relevant" in what we study, to restrict our field of knowledge, not only is the next generation missing out, we are on a very slippery slope indeed.
Bettany Hughes's latest book, Helen of Troy, Goddess, Princess, Whore, is published this week by Jonathan Cape. A documentary based on the book will appear on Channel 4 on October 22 Primary forum 24