Recent events in the Middle East and Europe seem to breathe fresh life into the “clash of civilisations” thesis. Western incursions into the Middle East have triggered an Islamic backlash that has driven millions of Muslim refugees westwards and inspired terrorist attacks from Orlando to Nice; now the EU is unravelling as European voters abandon multicultural dreams in favour of xenophobic local identities. Allegedly, this has happened because the west has chosen to ignore the deep logic of history. According to the clash of civilisations thesis, humankind has always been divided into diverse civilisations whose members view the world in different and often irreconcilable ways. These incompatible world views make conflicts between civilisations inevitable, and these conflicts in turn fuel long-term historical processes. Just as in nature different species fight for survival, so throughout history civilisations have repeatedly clashed, and only the fittest have survived. Those who overlook this grim fact do so at their peril.

The clash of civilisations thesis has far-reaching political implications. Its supporters contend that any attempt at reconciliation between “the west” and “the Muslim world” is doomed to failure. They further maintain that the EU can work only if it renounces the multicultural fallacy in favour of an unabashed “western” identity. In the long run, only one culture can survive the unforgiving tests of natural selection, and if the EU refuses to save western civilisation from Islamic State and its ilk, Britain had better go it alone.

Though widely held, this thesis is misleading. Isis may indeed pose a radical challenge, but the “civilisation” it challenges is a global civilisation rather than a uniquely western phenomenon. Not for nothing has Isis managed to unite Iran with the United States, and to create rare common ground between Israeli PM Binyamin Netanyahu and Hezbollah leader Hassan Nasrallah. And even Isis, for all its medieval rhetoric, is grounded in contemporary global culture far more than in seventh-century Arabia; it caters to the fears and hopes of alienated, postmodern youth rather than to those of medieval shepherds and merchants. In pure organisational terms, Isis has more in common with a large corporation like Google than with the Umayyad caliphate. The surest sign of a real clash of civilisations is mutual incomprehension. Isis, in contrast, comprehends its enemies only too well – otherwise, its propaganda would not have been so effective. It is better, therefore, to see Isis as an errant offshoot of the global culture we all share, rather than as a branch of some mysterious alien tree.

Human groups may have distinct social systems, but these seldom endure for more than a few centuries

Crucially, the analogy between history and biology that underpins the clash of civilisations thesis is false. Human groups – including human civilisations – are fundamentally different from animal species, and historical conflicts differ greatly from natural selection processes. Animal species have objective identities that endure for thousands of generations. Whether you are a chimpanzee or a gorilla depends on your genes rather than your beliefs, and different genes dictate diverse social behaviours. Chimpanzees live in mixed groups of males and females. They compete for power by building coalitions of supporters among both sexes. Among gorillas, in contrast, a single dominant male establishes a harem of females, and usually expels any adult male that might challenge his position. As far as we know, the same social systems have characterised chimpanzees and gorillas not only in recent decades, but for hundreds of thousands of years.

You find nothing like that among humans. Yes, human groups may have distinct social systems, but these are not genetically determined, and they seldom endure for more than a few centuries. Think of 20th-century Germans, for example. In fewer than 100 years, the Germans organised themselves into six very different systems: the Hohenzollern empire, the Weimar republic, the Third Reich, Communist East Germany, the federal republic of West Germany, and finally democratic reunited Germany. Of course they kept their language and love of beer. But is there some unique German essence that distinguishes their country from all other nations, and that has remained unchanged from Wilhelm II to Angela Merkel? And if you do come up with something, was it also there back in the days of Goethe, of Martin Luther and of Frederick Barbarossa?

What will happen when computers replace people in an increasing number of jobs? … Alex Proyas’s I, Robot from 2004 Photograph: Allstar

The Preamble of the European Constitution (2004) begins by stating that it draws inspiration “from the cultural, religious and humanist inheritance of Europe, from which have developed the universal values of the inviolable and inalienable rights of the human person, democracy, equality, freedom and the rule of law”. This may easily give one the impression that European civilisation is defined by these values. Countless speeches and documents draw a direct line from ancient Athenian democracy to the present-day EU, celebrating 2,500 years of European freedom and democracy. This is reminiscent of the proverbial blind man taking hold of an elephant’s tail and concluding that an elephant is a kind of brush. Athenian democracy was a half-hearted experiment that survived for barely 200 years in a small corner of the Balkans. If European civilisation for the last 25 centuries has been defined by democracy and human rights, what are we to make of Sparta and Julius Caesar, the Crusaders and Conquistadores, the Inquisition and the slave trade, Louis XIV and Goebbels, Lenin and Mussolini?

European civilisation is anything Europeans make of it, just as Christianity is anything Christians make of it. And they have made remarkably different things of it over the centuries. Human groups are defined more by the changes they undergo than by any continuity, but they nevertheless manage to create for themselves ancient identities thanks to their storytelling skills. No matter what revolutions they survive, they can weave old and new into a single yarn. Even an individual may knit revolutionary personal changes into a coherent life story: “I am that person who was once a socialist, but became a capitalist; I was born in Senegal, and now live in France; I married, then got divorced; I had cancer, and then got well again.”

Similarly, a human group such as the Germans may come to define itself by the very changes it has lived through: “Once we were Nazis, but we have learned our lesson, and now we are peaceful democrats”. You don’t need to look for some unique German essence that manifested itself first in Hitler and then in Merkel: this radical transformation itself makes the Germans who they are.

Isis, too, may uphold an allegedly unchanging Muslim identity, but their story of Islam is a brand new tale. Yes, they used some venerable Muslim texts and traditions to concoct it, but if I bake a cake from flour, oil and sugar that have been sitting in my pantry for the past two months, does it mean the cake itself is two months old? Conversely, those who dismiss Isis as “un-Islamic” or even “anti-Islamic” are equally mistaken: Islam has no DNA. Just as with Christianity, Islam is whatever Muslims make of it.

Isis wrecked the ancient site of Palmyra in Syria. Photograph: Valery Sharifulin/Tass

Yet there is an even deeper difference distinguishing human groups from animal species. Species often split, but never merge. About seven million years ago, chimpanzees and gorillas had common ancestors. This single ancestral species split into two populations that eventually went their separate, evolutionary ways. Once this happened, there was no going back. Since individuals belonging to different species cannot produce fertile offspring together, species can never merge. Gorillas can’t merge with chimpanzees, giraffes can’t merge with elephants, and dogs can’t merge with cats.

Human tribes, in contrast, tend to coalesce over time into larger and larger groups. Modern Germans were created from the merger of Saxons, Prussians, Swabians and Bavarians, which not so long ago wasted little love on one another. The French were created from the merger of Franks, Normans, Bretons, Gascons and Provencals. Meanwhile across the Channel, English, Scots, Welsh and Irish gradually came together (willingly or not) to form Britons. In the not too distant future, Germans, French and Britons might yet merge into Europeans.

Mergers don’t always last, as people in London, Edinburgh and Brussels are well aware these days. Brexit may well initiate the simultaneous unravelling of both the EU and the UK. But in the long run, history’s direction is clear-cut. Ten thousand years ago humankind was divided into countless isolated tribes. With each passing millennium, these merged into larger and larger groups, creating fewer and fewer distinct civilisations. In recent generations the few remaining civilisations have been merging into a single global community. Political and ethnic divisions endure, but they do not undermine the fundamental unity. Indeed, some divisions are made possible only by an over-arching common structure.

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The process of human unification has taken two distinct forms: weak heterogeneous unification and strong homogeneous unification. The weaker heterogeneous form involves creating ties between previously unrelated groups. The groups may continue to have different beliefs and practices, but are no longer independent of each other. From this perspective, even war is a bond – perhaps the strongest bond of all. Ten thousand years ago, no tribe in America had any quarrel with Middle Eastern enemies, and no African clan bore grudges towards any European. In contrast, during the second world war, people born on the shores of the Mississippi went to their deaths on Pacific islands and European meadows, while recruits from the heart of Africa fell fighting among French vineyards and Alpine snows.

Historians often argue that globalisation reached a first peak in 1913, then went into a long decline during the era of the world wars and the cold war, and recuperated only after 1989. They fear that new conflicts may again put globalisation into reverse gear. This may be true of economic globalisation, but it ignores the different but equally important dynamics of military globalisation. War spreads ideas, technologies and people far more quickly than commerce. War also makes people far more interested in one another. Never had the US been more closely in touch with Russia than during the cold war, when every cough in a Moscow corridor sent people scrambling up and down Washington staircases. People care far more about their enemies than about their trade partners. For every US film about Thailand, there are probably 20 about Vietnam. The global “war on terror” simply continues the process of military globalisation.

Photograph: Benoit Tessier/Reuters

Nowadays, the global unity of conflict is perhaps most apparent on the internet, where Isis and the drug cartels are rubbing shoulders with Google and Facebook, and YouTube offers funny cat videos alongside instructions on how to make bombs. Islamic fanatics, murderous drug dealers and geeky hackers don’t exist on unrelated planets; they share the same global cyberspace. All are thrilled by the blockchain technology that gave us the bitcoin; all count on easy accessibility via ubiquitous smartphones, and all are antagonised by national governments attempting to wrest control of the net.

Yet the world of the early 21st century has gone way beyond the heterogeneous unity of conflict. People across the globe are not only influenced by one another, they increasingly share identical beliefs and practices. A thousand years ago, planet Earth was home to dozens of different political models. In Europe you could find feudal principalities vying with independent city states and minuscule theocracies. The Muslim world had its caliphate, claiming universal sovereignty, but also experimented with kingdoms, emirates and sultanates. The Chinese empire believed itself to be the sole legitimate political entity, while to its north and west tribal confederacies fought each other with glee. India and south-east Asia contained a kaleidoscope of regimes, whereas polities in America, Africa and Australasia ranged from tiny hunter-gatherer bands to sprawling empires. No wonder even neighbouring human groups had trouble agreeing on diplomatic practices, not to mention international laws. Each society had its own political paradigms, and found it difficult to understand – let alone respect – alien political concepts.

Today there are nearly 200 sovereign states, which generally agree on diplomatic protocols and common international laws

Today, in contrast, a single political paradigm is accepted everywhere. The planet is divided between nearly 200 sovereign states, which generally agree on the same diplomatic protocols and on common international laws. Sweden, Nigeria, Papua New Guinea and Paraguay are all marked on our world maps as the same kind of colourful shapes; they are all members of the UN; and despite myriad differences they are all recognised as sovereign states enjoying similar rights and privileges. Indeed, they share many more political ideas and practices, including at least a token belief in representative bodies, universal suffrage and human rights. When Israelis and Palestinians, Russians and Ukrainians, or Kurds and Turks court global public opinion, they all use the same discourse of human rights, state sovereignty and international law.

The world may be peppered with various types of “failed states”, but it knows only one paradigm for a successful state. Global politics follows “the Anna Karenina principle”: healthy states are all alike, but every failed state fails in its own way, by missing this or that ingredient of the dominant political package. Isis stands out in its complete rejection of this package, and its attempt to establish an entirely different kind of political entity – a universal caliphate. But it is unlikely to succeed precisely for this reason. Numerous guerrilla forces and terror organisations have managed to establish new countries or conquer existing ones, but they have always done so by accepting the fundamental principles of the global political order. Even the Taliban sought international recognition as the legitimate government of the sovereign country of Afghanistan. No group rejecting the principles of global politics has so far gained lasting control of a significant territory.

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In pre-modern times, humans experimented not only with diverse political blueprints, but with a mind-boggling variety of economic models. Russian boyars, Hindu maharajas, Chinese mandarins and Amerindian tribal chiefs had very different ideas about money and taxation, and none was even aware of the existence of such a thing as “the economy”. Nowadays, in contrast, almost everybody believes in slightly different variations on the same capitalist theme, and we are all cogs within a single global production line. Whether you live in Mongolia, New Zealand or Bolivia, your daily routines and economic fortunes depend on the same economic theories, the same corporations and banks, and the same currents of capital. When finance ministers or bank managers from China, Russia, Brazil and India meet, they have a common language, and can easily understand and sympathise with their counterparts’ woes.

When Isis conquered large parts of Syria and Iraq, it murdered tens of thousands of people, demolished archaeological sites, toppled statues and systematically destroyed the symbols of previous regimes and of western cultural influence. Yet when Isis fighters entered the banks and found stashes of US dollars covered with the faces of American presidents and English slogans praising American political and religious ideals, they did not burn these dollars. For the dollar bill is universally venerated across all political and religious divides. Though it has no intrinsic value – you cannot eat or drink a dollar bill – trust in the dollar and in the wisdom of the Federal Reserve is so firm it is shared even by Islamic fundamentalists, Mexican drug lords and North Korean tyrants.

Doctors all over the word will dispense similar medicines made by the same drug companies Photograph: Alamy Stock Photo

Yet the homogeneity of contemporary humanity is most apparent when it comes to our view of the natural world and of the human body. If you fell sick in 1016, it mattered a great deal where you lived. In Europe, the resident priest would probably tell you that you had made God angry, and that in order to regain your health, you should donate something to the church, make a pilgrimage to a sacred site, and pray fervently for God’s forgiveness. Alternatively, the village witch might explain that a demon had possessed you, and that she could cast the demon out using song, dance and the blood of a black cockerel. In the Middle East, doctors brought up on classical traditions might explain that your four bodily humours were out of balance, and you could harmonise them anew with a proper diet and foul-smelling potions. In India, Ayurvedic experts would offer their own theories concerning the balance between the three bodily elements known as doshas, and recommend a treatment of herbs, massages and exercises. Chinese physicians, Siberian shamans, African witch doctors, Amerindian medicine men – every empire, kingdom and tribe had its own traditions and experts, each espousing different views about the human body and the nature of sickness, and each offering its own cornucopia of rituals, concoctions and cures. Some of them worked surprisingly well; others were little short of a death sentence. The one thing that united European, Chinese, African and American medical conditions was that everywhere at least a third of people died before adulthood, and nowhere did average life expectancy exceed 40.

Today, if you are taken ill, it makes far less difference where you live. In Toronto, Tokyo, Tehran or Tel Aviv, you will be taken to similar-looking hospitals, where you will meet doctors who learned the same scientific theories in not-too-different medical colleges. They will follow identical protocols and use identical tests to reach very similar diagnoses. They will then dispense similar medicines made by the same drug companies. There are still some minor cultural differences, but Canadian, Japanese, Iranian and Israeli physicians hold much the same views about the human body and human diseases. After Isis captured Raqqa and Mosul, it did not tear down the hospitals; rather, it launched an appeal to Muslim doctors and nurses throughout the world to volunteer their services there. Presumably, even Isis doctors and nurses believe that the body is made of cells, that diseases are caused by pathogens, and that antibiotics kill bacteria.

And what makes up these cells and bacteria? Indeed, what makes up the entire world? Back in 1016, every culture had its own story about the universe, and about the fundamental ingredients of the cosmic soup. Today, learned people throughout the world believe exactly the same things about matter, energy, time and space. Take, for example, Iran’s nuclear programme. The whole problem with it is that the Iranians have exactly the same view of physics as the Israelis and Americans. If the Iranians believed that E=mc⁴, Israel would not care an iota about their nuclear programme.

Churchill wasn’t more western than Hitler; their struggle defined what it meant to be western at that moment in history

People still claim to believe in different things. But when it comes to the really important stuff – how to build a state, an economy, a hospital, or a weapon – almost all of us belong to the same civilisation. There are disagreements, no doubt, but then all civilisations have their internal disagreements – indeed, they are defined by these disagreements. When trying to outline their identity, people often make a grocery list of common traits. They would fare much better if they made a list of common conflicts and dilemmas instead. In 1940, Britain and Germany had very different traits, yet they were both part and parcel of “western civilisation”. Churchill wasn’t more western than Hitler; rather, the struggle between them defined what it meant to be western at that particular moment in history. In contrast, a !Kung hunter-gatherer in 1940 wasn’t western, because the internal western clash about race and empire would have made little sense to him.

The people we fight most often are our own family members. Identity is defined by conflicts and dilemmas more than by agreements. What does it mean to be European in 2016? It doesn’t mean to have white skin, to believe in Jesus Christ, or to uphold liberty. Rather, it means to argue vehemently about immigration, about the EU, and about the limits of capitalism. It also means to obsessively ask yourself “What defines my identity?” and to worry about an ageing population, about rampant consumerism and about global warming without really knowing what to do about it. In their conflicts and dilemmas, 21st-century Europeans are very different from their early-modern and medieval ancestors, but are increasingly similar to their Chinese and Indian contemporaries.

Whatever changes await us, they are likely to involve a fraternal struggle within a single civilisation rather than a clash between alien civilisations. The big challenges of the 21st century will be global in nature. What will happen when pollution triggers global climate changes? What will happen when computers replace people in an increasing number of jobs? When biotechnology enables us to upgrade humans, extend lifespans, and perhaps split humankind into different biological castes? No doubt, we will have huge arguments and bitter conflicts over these questions. But these arguments and conflicts are unlikely to drive us apart. Just the opposite. They will make us ever more interdependent, as members of a single, rowdy, global civilisation.

• Yuval Noah Harari’s Homo Deus: A Brief History of Tomorrow is published by Harvill Secker. ynharari.com