A few years ago, Gibraltar issued a set of stamps commemorating the Rock's Neanderthal heritage. There is much to celebrate. Gibraltar was the site of the discovery of the first Neanderthal skull. Gibraltar was home to the Neanderthals for tens of thousands of years. Gibraltar was the Neanderthals' final European resting place before they became extinct. Today, 35,000 years on, Gibraltar offers the human race an opportunity to take another mighty step up the evolutionary ladder. The choice of whether to seize the opportunity or let it pass has fallen on Spain.
The result of the referendum on Gibraltar's future - in which the rocky outcrop's 30,000 inhabitants will be asked if they wish to cede partial sovereignty to Spain - is a foregone conclusion and will in any case probably be known for sure by the time you read this. The Spanish have been claiming Gibraltar since 1713, when Philip V surrendered it to Britain "to be held and enjoyed absolutely with all manner of right, for ever". As a glance at the map will tell you, the Spanish have a very good point, indeed. However, the Gibraltarians feel British, are British and, motley bunch though they might be (Christians, Muslims and Jews of Genoese and Maltese descent, who mostly speak Spanish at home), British they wish to remain. Which is why they have unilaterally appealed to the democratic conscience of the world, or to whoever in the world may be paying attention, and held a referendum derided by Britain as a waste of money and by Spain as futile meddling.
Yet it could be the best use to which taxpayers' money has been put since Ferdinand and Isabella funded Columbus's voyage to America. If only the Spanish would show a bit of a sense of humour, if only they would stop being so precious, abandon their characteristic huffiness on matters of national pride and rise, Quixote-like, to the occasion, they have it in their grasp to secure humanity's admiration and gratitude for the rest of time. All they have to do is perform the most generous, most unexpected volte-face in history and respond to the democratic will of the Gibraltarian people by declaring that they have resolved to renounce all sovereign claims to a piece of land that is, by just about every conventional measure, so manifestly theirs. And in so doing send a message to the planet that nationalism be damned, condemning to the Darwinian dustbin the impulse to drape paltry instinct in the flag of war, to dress up paranoia as a noble cause.
For Spain to relinquish Gibraltar is not like the British empire relinquishing India or - for that matter - like Spain relinquishing Mexico or Argentina. It would be something far more momentous. This is partly because, geographically, Gibraltar is to Spain as Land's End is to Britain, or Florida to the US. But, above all, it is because the Spanish would forfeit their ancient claim in a perfect act of free will. They would agree voluntarily to what Philip V agreed under duress, and in so doing liberate the human mind of one of its most enduringly pernicious shackles. It would be a pivotal episode in the history of the earth, like that scene in Stanley Kubrick's 2001: A Space Odyssey, where a tall, black, rectangular slab emerges out of nowhere in the colony of apes, announcing, to a blast of Strauss, that life on the planet will never be the same again.
It would also have an impact on Spain itself, where the bane of modern times has been Basque nationalism and the terrorism that attends it. Members of ETA would be shaken by Spain's act of renunciation into at least a reappraisal of their primitive beliefs. And perhaps if they insisted on clinging to them, the rest of Spain would hold a referendum of its own on whether it should not itself secede from the Basques. All kinds of happy consequences might then follow.
Inspired by Spain's moral heroism, the scales that have so blinded the species might lift, leaving open the way for Argentina to consider abandoning its sovereign claim to the Falklands, China to Tibet, Pakistan (or India) to Kashmir, Guatemala to Belize, Israel to Palestine, the US to Texas, Morocco to Parsley Island. If only Spain would seize the day.