Homo Deus: A Brief History of Tomorrow

by Yuval Noah Harari

The theory of relativity makes nobody angry, because it doesn’t contradict any of our cherished beliefs.

Our eye is very similar to the eye of Homo erectus, who lived 1 million years ago. It is somewhat less similar to the eye of Australopithecus, who lived 5 million years ago. It is very different from the eye of Dryolestes, who lived 150 million years ago.

Natural selection could produce a human eye, because the eye has parts. But the soul has no parts.

The better we understand the brain, the more redundant the mind seems.

Philosophers have encapsulated this riddle in a trick question: what happens in the mind that doesn’t happen in the brain? If nothing happens in the mind except what happens in our massive network of neurons – then why do we need the mind? If something does indeed happen in the mind over and above what happens in the neural network – where the hell does it happen?

what’s wrong with torture or rape? From a purely neurological perspective, when a human is tortured or raped certain biochemical reactions happen in the brain, and various electrical signals move from one bunch of neurons to another. What could possibly be wrong with that? Most modern people have ethical qualms about torture and rape because of the subjective experiences involved. If any scientist wants to argue that subjective experiences are irrelevant, their challenge is to explain why torture or rape are wrong without reference to any subjective experience.

consciousness may be a kind of mental pollution produced by the firing of complex neural networks. It doesn’t do anything. It is just there.

For all you know, the year might be 2216 and you are a bored teenager immersed inside a ‘virtual world’ game that simulates the primitive and exciting world of the early twenty-first century. Once you acknowledge the mere feasibility of this scenario, mathematics leads you to a very scary conclusion: since there is only one real world, whereas the number of potential virtual worlds is infinite, the probability that you happen to inhabit the sole real world is almost zero.

The Turing Test was invented in 1950 by the British mathematician Alan Turing, one of the fathers of the computer age. Turing was also a gay man in a period when homosexuality was illegal in Britain. In 1952 he was convicted of committing homosexual acts and forced to undergo chemical castration. Two years later he committed suicide. The Turing Test is simply a replication of a mundane test every gay man had to undergo in 1950s Britain: can you pass for a straight man? Turing knew from personal experience that it didn’t matter who you really were – it mattered only what others thought about you. According to Turing, in the future computers would be just like gay men in the 1950s. It won’t matter whether computers will actually be conscious or not. It will matter only what people think about it.

emotions are algorithms, and that no known algorithm requires consciousness in order to function.

In essence, we humans are not that different from rats, dogs, dolphins or chimpanzees. Like them, we too have no soul. Like us, they too have consciousness and a complex world of sensations and emotions. Of course, every animal has its unique traits and talents. Humans too have their special gifts. We shouldn’t humanise animals needlessly, imagining that they are just a furrier version of ourselves. This is not only bad science, but it also prevents us from understanding and valuing other animals on their terms.

Over those 20,000 years humankind moved from hunting mammoth with stone-tipped spears to exploring the solar system with spaceships not thanks to the evolution of more dexterous hands or bigger brains (our brains today seem actually to be smaller).17 Instead, the crucial factor in our conquest of the world was our ability to connect many humans to one another.18 Humans nowadays completely dominate the planet not because the individual human is far smarter and more nimble-fingered than the individual chimp or wolf, but because Homo sapiens is the only species on earth capable of co-operating flexibly in large numbers.

Bees cooperate in very sophisticated ways, but they cannot reinvent their social system overnight. If a hive faces a new threat or a new opportunity, the bees cannot, for example, guillotine the queen and establish a republic.

If you want to launch a revolution, don’t ask yourself, ‘How many people support my ideas?’ Instead, ask yourself, ‘How many of my supporters are capable of effective collaboration?’

All this happened live on Romanian television, as three-quarters of the populace sat glued to the screens, their hearts throbbing wildly. The notorious secret police – the Securitate – immediately ordered the broadcast to be stopped, but the television crews disobeyed.

His wife Elena began scolding the audience, ‘Be quiet! Be quiet!’ until Ceaușescu turned and yelled at her – still live on television – ‘You be quiet!’ Ceaușescu then appealed to the excited crowds in the square, imploring them, ‘Comrades! Comrades! Be quiet, comrades!’

Ceauşescu and his cronies dominated 20 million Romanians for four decades because they ensured three vital conditions. First, they placed loyal communist apparatchiks in control of all networks of cooperation, such as the army, trade unions and even sports associations. Second, they prevented the creation of any rival organisations – whether political, economic or social – which might serve as a basis for anti-communist cooperation. Third, they relied on the support of sister communist parties in the Soviet Union and eastern Europe.

Yet when power slipped from the hands of the clumsy organiser on the balcony, it did not pass to the masses in the square. Though numerous and enthusiastic, the crowds did not know how to organise themselves. Hence just as in Russia in 1917, power passed to a small group of political players whose only asset was good organisation. The Romanian Revolution was hijacked by the self-proclaimed National Salvation Front, which was in fact a smokescreen for the moderate wing of the Communist Party.

In communist Romania almost everything was owned by the state. Democratic Romania quickly privatised its assets, selling them at bargain prices to the ex-communists, who alone grasped what was happening and collaborated to feather each other’s nests.

However, it is one thing to bring 100,000 people to Tahrir Square, and quite another to get a grip on the political machinery, shake the right hands in the right back rooms and run a country effectively. Consequently, when Mubarak stepped down the demonstrators could not fill the vacuum. Egypt had only two institutions sufficiently organised to rule the country: the army and the Muslim Brotherhood. Hence the revolution was hijacked first by the Brotherhood, and eventually by the army.

If Sapiens rule the world because we alone can cooperate flexibly in large numbers, then this undermines our belief in the sacredness of human beings.

A beehive has much greater power than an individual butterfly, yet that doesn’t imply a bee is therefore more hallowed than a butterfly. The Romanian Communist Party successfully dominated the disorganised Romanian population. Does it follow that the life of a party member was more sacred than the life of an ordinary citizen? Humans know how to cooperate far more effectively than chimpanzees, which is why humans launch spaceships to the moon whereas chimpanzees throw stones at zoo visitors. Does it mean that humans are superior beings?

Among pygmy chimpanzees – also known as bonobos – things are a bit different. Bonobos often use sex in order to dispel tensions and cement social bonds. Not surprisingly, homosexual intercourse is consequently very common among them. When two alien groups of bonobos encounter one another, at first they display fear and hostility, and the jungle is filled with howls and screams. Soon enough, however, females from one group cross no-chimp’s-land, and invite the strangers to make love instead of war. The invitation is usually accepted, and within a few minutes the potential battlefield teems with bonobos having sex in almost every conceivable posture, including hanging upside down from trees.

The Ultimatum Game made a significant contribution to undermining classical economic theories and to establishing the most important economic discovery of the last few decades: Sapiens don’t behave according to a cold mathematical logic, but rather according to a warm social logic.

We are ruled by emotions. These emotions, as we saw earlier, are in fact sophisticated algorithms that reflect the social mechanisms of ancient hunter-gatherer bands. If 30,000 years ago I helped you hunt a wild chicken and you then kept almost all the chicken to yourself, offering me just one wing, I did not say to myself: ‘Better one wing than nothing at all.’ Instead my evolutionary algorithms kicked in, adrenaline and testosterone flooded my system, my blood boiled, and I stamped my feet and shouted at the top of my voice. In the short term I may have gone hungry, and even risked a punch or two. But it paid off in the long term, because you thought twice before ripping me off again. We refuse unfair offers because people who meekly accepted unfair offers didn’t survive in the Stone Age.

The second monkey, who was previously very happy with his cucumber, became incensed. He took the cucumber, looked at it in disbelief for a moment, and then threw it at the scientists in anger and began jumping and screeching loudly. He ain’t a sucker.

People are egalitarian by nature, and unequal societies can never function well due to resentment and dissatisfaction.

As Frederick watched his troops assemble for the invasion, he told one of his generals that what struck him most about the scene was that ‘we are standing here in perfect safety, looking at 60,000 men – they are all our enemies, and there is not one of them who is not better armed and stronger than we are, and yet they all tremble in our presence, while we have no reason whatsoever to be afraid of them’.

The leaders of the second group might well accept this unfair offer, siphon most of the $10 billion into their Swiss bank accounts, while preventing rebellion among their followers with a combination of sticks and carrots.

As long as all Sapiens living in a particular locality believe in the same stories, they all follow the same rules, making it easy to predict the behaviour of strangers and to organise mass-cooperation networks. Sapiens often use visual marks such as a turban, a beard or a business suit to signal ‘you can trust me, I believe in the same story as you’. Our chimpanzee cousins cannot invent and spread such stories, which is why they cannot cooperate in large numbers.

People find it difficult to understand the idea of ‘imagined orders’ because they assume that there are only two types of realities: objective realities and subjective realities.

However, there is a third level of reality: the intersubjective level. Intersubjective entities depend on communication among many humans rather than on the beliefs and feelings of individual humans.

At 2 p.m. on 8 December 1991, in a state dacha near Viskuli, the leaders of Russia, Ukraine and Belarus signed the Belavezha Accords, which stated that ‘We, the Republic of Belarus, the Russian Federation and Ukraine, as founding states of the USSR that signed the union treaty of 1922, hereby establish that the USSR as a subject of international law and a geopolitical reality ceases its existence.’

Meaning is created when many people weave together a common network of stories. Why does a particular action – such as getting married in church, fasting on Ramadan or voting on election day – seem meaningful to me? Because my parents also think it is meaningful, as do my brothers, my neighbours, people in nearby cities and even the residents of far-off countries.

Imagine a young English nobleman named John, who left home to fight Saladin. John believed that his actions had an objective meaning. He believed that if he died on the crusade, after death his soul would ascend to heaven, where it would enjoy everlasting celestial joy. He would have been horrified to learn that the soul and heaven are just stories invented by humans. John wholeheartedly believed that if he reached the Holy Land, and if some Muslim warrior with a big moustache brought an axe down on his head, he would feel an unbearable pain, his ears would ring, his legs would crumble under him, his field of vision would turn black – and the very next moment he would see brilliant light all around him, he would hear angelic voices and melodious harps, and radiant winged cherubs would beckon him through a magnificent golden gate.

In the Middle Ages people would have thought he had gone bonkers. Nobody in twelfth-century England knew what human rights were. You want to travel to the Middle East and risk your life not in order to kill Muslims, but to protect one group of Muslims from another? You must be out of your mind.

It all began about 70,000 years ago, when the Cognitive Revolution enabled Sapiens to start talking about things that existed only in their own imagination. For the ensuing 60,000 years Sapiens wove many fictional webs, but these remained small and local. The spirit of a revered ancestor worshipped by one tribe was completely unknown to its neighbours, and seashells valuable in one locality became worthless once you crossed the nearby mountain range. Stories about ancestral spirits and precious seashells still gave Sapiens a huge advantage, because they allowed hundreds and sometimes even thousands of Sapiens to cooperate effectively, which was far more than Neanderthals or chimpanzees could do. Yet as long as Sapiens remained hunter-gatherers they could not cooperate on a truly massive scale, because it was impossible to feed a city or a kingdom by hunting and gathering. Consequently the spirits, fairies and demons of the Stone Age were relatively weak entities.

The Agricultural Revolution, which began about 12,000 years ago, provided the necessary material base for enlarging and strengthening the intersubjective networks. Farming made it possible to feed thousands of people in crowded cities and thousands of soldiers in disciplined armies. However, the intersubjective webs then encountered a new obstacle. In order to preserve the collective myths and organise mass cooperation, the early farmers relied on the data-processing abilities of the human brain, which were strictly limited.

Today, corporations are fictional legal entities that own property, lend money, hire employees and initiate economic enterprises. In the ancient cities of Uruk, Lagash and Shurupak the gods functioned as legal entities that could own fields and slaves, give and receive loans, pay salaries and build dams and canals.

This obstacle was finally removed about 5,000 years ago, when the Sumerians invented both writing and money.

Writing and money made it possible to start collecting taxes from hundreds of thousands of people, to organise complex bureaucracies and to establish vast kingdoms.

For example, pharaohs Senusret III and his son Amenemhat III, who ruled Egypt from 1878 BC to 1814 BC, dug a huge canal linking the Nile to the swamps of the Fayum Valley. An intricate system of dams, reservoirs and subsidiary canals diverted some of the Nile waters to Fayum, creating an immense artificial lake holding 13 trillion gallons of water.1 By comparison, Lake Mead, the largest man-made reservoir in the United States (formed by the Hoover Dam), holds at most 9 trillion gallons of water.

The Fayum engineering project gave pharaoh the power to regulate the Nile, prevent destructive floods and provide precious water relief in times of drought. In addition, it turned the Fayum Valley from a crocodile-infested swamp surrounded by barren desert into Egypt’s granary. On the shore of the new artificial lake was built the new city of Shadet, which the Greeks called Crocodilopolis – the city of crocodiles. It was dominated by the temple of the crocodile god Sobek, who was identified with pharaoh (contemporary statues sometimes show pharaoh sporting a crocodile head). The temple housed a sacred crocodile called Petsuchos, who was considered to be the living incarnation of Sobek. Just like the living-god pharaoh, the living-god Petsuchos was lovingly groomed by attending priests who provided the lucky reptile with lavish food and even toys, and dressed him up in gold cloaks and gem-encrusted crowns. After all, Petsuchos was the priests’ brand, and their authority and livelihood depended on him. When Petsuchos died, a new crocodile was immediately elected to fill his sandals, while the dead reptile was carefully embalmed and mummified.

Sousa Mendes, armed with little more than a rubber stamp, was responsible for the largest rescue operation by a single individual during the Holocaust.

In fact, within less than ten years Tanzania was transformed from Africa’s biggest food exporter into a net food importer that could not feed itself without external assistance. In 1979, 90 per cent of Tanzanian farmers lived on collective farms, but they generated only 5 per cent of the country’s agricultural output.

In the late nineteenth century, several European powers laid claim to African territories. Fearing that conflicting claims might lead to an all-out European war, the concerned parties got together in Berlin in 1884 and divided Africa as if it were a pie. Back then much of the African interior was terra incognita to Europeans. The British, French and Germans had accurate maps of Africa’s coastal regions, and knew precisely where the Niger, Congo and Zambezi empty into the ocean. However, they knew little about the course these rivers took inland, about the kingdoms and tribes that lived along their banks, and about local religion, history and geography. This hardly mattered to the European diplomats. They unrolled a half-empty map of Africa over a well-polished Berlin table, sketched a few lines here and there, and divided the continent among them.

It was the mass education systems of the industrial age that began using precise marks on a regular basis. After both factories and government ministries became accustomed to thinking in the language of numbers, schools followed suit. They started to gauge the worth of each student according to his or her average mark, whereas the worth of each teacher and principal was judged according to the school’s overall average. Once bureaucrats adopted this yardstick, reality was transformed.

If you distort reality too much, it will weaken you, and you will not be able to compete against more clear-sighted rivals. On the other hand, you cannot organise masses of people effectively without relying on some fictional myths. So if you stick to unalloyed reality, without mixing any fiction with it, few people will follow you.

Thus the ancient Jews believed that if they suffered from drought, or if King Nebuchadnezzar of Babylonia invaded Judaea and exiled its people, surely these were divine punishments for their own sins. And if King Cyrus of Persia defeated the Babylonians and allowed the Jewish exiles to return home and rebuild Jerusalem, God in his mercy must have heard their remorseful prayers. The Bible doesn’t recognise the possibility that perhaps the drought resulted from a volcanic eruption in the Philippines, that Nebuchadnezzar invaded in pursuit of Babylonian commercial interests and that King Cyrus had his own political reasons to favour the Jews. The Bible accordingly shows no interest whatsoever in understanding the global ecology, the Babylonian economy or the Persian political system.