First World, Third World, East, West, North and South; every few years economists come up with yet another supposedly more acceptable way of slicing humanity into manageable chunks. Mostly these great divides are riven by wealth; sometimes (RIP Second World) by ideology.

But I think it’s time to name a new divide, a more fundamental, more puzzling one — a split between worlds that will define the 21st century much as the Iron Curtain defined the 20th. I am talking about the morality gap.

It is now clear, though not much talked about, that humanity, all 7.1 billion of us, tends to fall into one of two distinct camps. On the one side are those who buy into the whole post-Enlightenment human rights revolution. For them the moral trajectory of the last 300 years is clear: once we were brutal savages; in a few decades, the whole planet will basically be Denmark, ruled by the shades of Mandela and Shami Chakrabarti.

And there’s some truth in this trajectory — except for the fact that it only applies to half the planet. The other half resolutely follows a different moral code: might is right, all men were not created equal and there is a right and a wrong form of sexual orientation.

You can identify those countries in the dark half of the divide by their attitudes to homosexuality and women; to honour killings, race, disability, mental illness, religious minorities and to crime, torture and punishment, even animal rights and the environment.

This gap is new (only about 60 years old in fact) but it is widening and deepening every year. Put simply, and brutally, for about two billion people, living mostly in Europe, the Americas, Australasia and eastern Asia, the attitudes prevailing in the rest of the world are beyond the pale and getting further beyond it by the minute.

So what is going on? Let’s start with attitudes to gays, not because gay rights are the most important issue, but because attitudes to homosexuality show the morality gap in sharpest relief.

Fifty years ago, male homosexual acts were illegal in both the US and much of Europe, including Britain. The idea that two men — or women — could marry, inherit pensions and adopt children would have seemed an absurdity in Macmillan’s Britain, never mind Attlee’s.

Fast forward to 2013. Britain has a posh, Eton-educated Tory Prime Minster who is proselytising for gay marriage. In many countries it is now illegal to discriminate against gays on any grounds. And this is not just a political hobbyhorse; the most recent British Social Attitudes Survey illustrates the astonishing wave of liberalism that has swept our nation. As recently as 1983, 50 per cent of those polled thought same-sex relationships were ‘always wrong’; by last year that number had dropped to just 22 per cent. We are simply not bothered, and becoming less bothered every year. As long as they do no harm, individuals are increasingly free to choose their own way of life without being condemned by their community.

Similar trends are found across a swath of northern Europe, much of the US and Canada, Latin America, Israel and much of east Asia. A look at the timeline of gay rights shows a seemingly unstoppable barrage of permissiveness, with state after state passing laws first legalising homosexuality, then going further: permitting gay marriage and gay adoption and formalising gay relationships in terms of pensions and property rights. It’s tempting for those of us in this enlightened half of the world to think of this as a great wave of progress that rose up in the mid-20th century and will sweep across the world.

Tempting, but wrong. In fact, in much of the world, received wisdom on homosexuality appears to be going into reverse. Across the old USSR, Africa, south-western Asia and the Caribbean, huge numbers of people hold views that, were they to be expressed openly here, could land them in prison.

In 2006, the Republic of Cameroon’s leading newspapers vied to ‘out’ a series of prominent gays, the editors saying they had a duty to expose ‘deviant behaviour’. The publisher of the weekly L’Anecdote, Jean Pierre Amougou Belinga, defended headlines such as ‘Gays are among us!’ and Yaoundé’s answer to Kelvin MacKenzie promised more revelations to come. ‘We could not remain silent. We had to ring the alarm bell.’

It is tempting to believe that this is simply the time lag at work; just as Africa and the Muslim world catch up with the West economically, they will catch up with us in permissiveness as well.

But there is little sign that this is actually happening. Africa is — hearteningly — getting richer. But it is not getting more tolerant. Uganda is in trouble for debating laws that would make it illegal not only to be gay (which it already is) but illegal not to report gay people to the police. It is hard to imagine any European politician — even the nutters of Golden Dawn — arguing for that.

Guardian-ista opinion excuses Middle Eastern, African and Caribbean homophobia by blaming ‘colonial era’ laws, but these countries have had decades to repeal the laws and have chosen not to do so.

Why? The non-partisan American think tank Pew Research Center has the answer. It carries out social attitudes surveys in Africa, and the most recent one found that in most African countries between 80 and 98 per cent of the population believe homosexual behaviour to be ‘morally wrong’. Even in Russia, gay rights are in retreat. President Vladimir Putin signed a law at the end of June prohibiting the promotion of nontraditional sexual relationships to minors. It has been interpreted as banning gay pride parades — children might see them — and preventing talk of homosexuality among teenagers.

The morality gap is not, of course, just about gay rights. Recently a disturbing survey conducted by the UN found that a quarter of all men in the ‘Asia Pacific’ region have admitted committing rape. The survey was flawed — I am not entirely clear how they define the region in question (Papua New Guinea is in, as is China, but for some reason Japan is not, and there is the whole problem of self-reporting bias) but even so, a quarter. If a poll found eight million British men (or 40 million Americans) cheerfully admitting to being rapists, we would go into shock. But in a culture where men are dominant and their needs privileged over women’s, it becomes alarmingly normal.

The two worlds are moving further apart. While we agonise about glass ceilings and discrimination — beatings, torture, rape and floggings are de rigueur at police stations across the world. Again, it is fashionable to blame ‘poverty’ for this state of affairs, but rich old Saudi Arabia still cuts people’s heads off in public, bans women from driving and tortures with impunity.

There has been a lot of debate about the seeming lunacy of the UK giving aid money to India. But actually there is a moral case for doing so, if only we’d admit it, which is that rich Indians, of whom there are many, don’t much care about poor ones — at least not nearly enough of them do.

Most of Europe has a homicide rate of 0 to 2 people per 100,000 per year (in the UK it is 1.2). This low baseline rate is now matched by several Asian countries, including Japan, Singapore and Hong Kong. But in the rest of the world things are a little different. The murder rate in South Africa is 69 per 100,000. In Colombia it is 52. In most of the Third World you are between ten and a hundred times more likely to die a violent death than you are here.

People persist in thinking that time will close the morality gap. According to Steven Pinker, whose 2011 book The Better Angels of our Nature charts the extraordinary decline in human violence, the ‘civilising process’ that saw an end to burning, flogging, mass rape, hanging, judicial torture, slavery and homicide stats that made modern Detroit seem like Oslo began in Europe and spread outward. ‘In the late 1800s, Europe had a peaceable bull’s eye in the northern industrialised countries — Great Britain, France, Germany, Denmark and the Low Countries’.

This peaceability spread east and south because, says Pinker, of the spread of information about the world (the more we learn about each other, the less we want to kill each other) and the industrial and scientific revolutions that freed us from the tyranny of mass poverty, class divides and primitivism.

My fear is that the spread of peaceability has stalled, and we’re too politically correct to point it out. We simply cannot accept that there are several billion people out there who do not think as we do, and perhaps never will. So we prefer to focus on trivia.

Recently, Amnesty International became het up about the fact that in Denmark the penal code has an ambiguous definition of rape-within-marriage, calling it ‘disturbing’.

No doubt the Danes could do better, but: have a sense of perspective! For most women in this world, rape is commonplace, and moreover in many places hardly any women dare to report it, not because they don’t think they will be believed, but because they will be raped again by the policemen and then murdered by their own family. How can we agonise about Danish laws — Danish! — when every year several million girls in 28 countries suffer genital mutilation in the name of ‘purity’?

This is not to say that Africans or Russians or Muslims are intrinsically worse people than, say, the British or the Danes. This is not about race or nationality. There are people alive who were involved in the quite legal persecution of British homosexuals in the 1950s and 60s. Our grandparents’ generation was on the same side of the morality gap as today’s Saudis and the Ugandans. We used to be ghastly, and hold ghastly views. And we in the West do some things that Africans and Middle Easterners find repugnant, and rightly so, especially the appalling way we treat our elderly.

Nor am I arguing that one has to accept the changes in mores in most western countries as ‘right’. You may support capital punishment and hate the gay liberation movement, but the fact is that if you live in the West, your views are increasingly out of kilter.

A moral gap is dividing us — one we really don’t need in this ever more crowded world. Let’s hope everyone eventually learns to behave.