This is a section-by-section summary and review of Sapiens: A Brief History of Humankind by Yuval Noah Harari. It's come up on Less Wrong before in the context of Death is Optional, a conversation the author had with Daniel Kahneman about the book, and seems like an accessible introduction to many of the concepts underlying the LW perspective on history and the future. Anyone who's thought about Moloch will find many of the same issues discussed here, and so I'll scatter links to Yvain throughout. I'll discuss several of the points that I thought were interesting and novel, or at least had a novel perspective and good presentation.

A history as expansive as this one necessarily involves operating on higher levels of abstraction. The first section expresses this concisely enough to quote in full:

About 13.5 billion years ago, matter, energy, time and space came into being in what is known as the Big Bang. The story of these fundamental features of our universe is called physics.

About 300,000 years after their appearance, matter and energy started to coalesce into complex structures, called atoms, which then combined into molecules. The story of atoms, molecules and their interactions is called chemistry.

About 3.8. billion years ago, on a planet called Earth, certain molecules combined to form particularly large and intricate structures called organisms. The story of organisms is called biology.

About 70,000 years ago, organisms belonging to the species Homo sapiens started to form even more elaborate structures called cultures. The subsequent development of these human cultures is called history.

Three important revolutions shaped the course of history: the Cognitive Revolution kick-started history about 70,000 years ago. The Agricultural Revolution sped it up about 12,000 years ago. The Scientific Revolution, which got under way only 500 years ago, may well end history and start something completely different. This book tells the story of how these three revolutions have affected humans and their fellow organisms.

The main charm of the book, as I see it, is what I would call the "view from Mars," or what others might call the "outside view" or "view from nowhere." We live in the middle of the Scientific Revolution, of history, biology, chemistry, and physics, and it is hard to imagine the days when biology was *new*. Overarching histories like this help clarify and separate the regimes and underlying trends, which is useful for understanding the past, predicting the future, and directing our efforts.

Following Harari, I'll use "humans" to refer to the members of the genus homo, and Sapiens to refer to homo Sapiens specifically. I'll use "kya" to refer to "kiloyears ago," or thousands of years before now. Harari splits his book into four parts: The Cognitive Revolution, The Agricultural Revolution, The Unification of Humankind, and The Scientific Revolution. I'll discuss those parts separately before giving my thoughts on the whole. Compared to previous reviews I've written for Less Wrong, I'm going to employ quotes far more heavily, primarily because Harari is a good writer who climbs the ladder of abstraction up and down very well, so he often self-summarizes.

The Cognitive Revolution

Harari attributes the cognitive revolution to the ability of Sapiens language (and brains) to communicate about fictions. From an individual perspective, this seems problematic: an individual who only believes true things seems strictly more fit than an individual who believes both true and false things.

But from a collective perspective, fictions can allow cooperation on a much broader scale. This is the first obvious benefit of starting from the lower levels and building up--if you were a Martian biologist, the striking thing about Sapiens is their tremendous ability to cooperate with each other. Other animals do not build cities, and would not find them livable, because there would be too many of their own kind there. But to a city-dwelling human, that humans can meet strangers with only a touch of anxiety seems normal, not necessarily odd enough to demand a powerful explanation.

Many different varieties of animals have tribes, of course, but there doesn't seem to have been much social difference between chimpanzee tribes, elephant tribes, and pre-Cognitive Revolution Sapiens tribes. The social roles of those tribes are often recognizable to us. Typically, the tribe has coalitions that are maintained by close social relationships, frequent contact, and (if the language is developed enough) gossip. But this puts a hard limit on the growth potential of tribes--eventually, the marginal coalition member will get more by joining another coalition than they will from joining the largest coalition, because the largest coalition doesn't have any spare energy, attention, or resources to devote to the potential new member. 

But when we go from cooperating based on truth--that we groomed each other yesterday--to cooperating based on fiction--that both of us are intellectual heirs of Bacon and Laplace--the practicalities of group membership change dramatically. We don't have just coalitions supported by pairwise relationships, by principle-oriented factions, where each person in the faction has a relationship primarily with the faction. (Two articles by Yvain, Is Everything a Religion? and I Can Tolerate Everything Except the Outgroup, seem relevant.)

Strictly speaking, of course, the principles underlying the faction do not "exist." As Harari puts it:

There are no gods in the universe, no nations, no money, no human rights, no laws, and no justice outside the common imagination of human beings.

People easily understand that 'primitives' cement their social order by believing in ghosts and spirits, and gathering each full moon to dance together around the campfire. What we fail to appreciate is that our modern institutions function on exactly the same basis.

But, of course, those modern institutions (as well as the 'primitive' ones) function. One division Harari discusses that I found useful was objective, subjective, and inter-subjective:

An objective phenomenon exists independently of human consciousness and human beliefs. ... [Radioactivity is his example.]

The subjective is something that exists depending on the consciousness and beliefs of a single individual. ... [A child's imaginary friend is his example.]

The inter-subjective is something that exists within the communication network linking the subjective consciousness of many individuals. If a single individual changes his or her beliefs, or even dies, it is of little importance. However, if most individuals in the network die or change their beliefs, the inter-subjective phenomenon will mutate or disappear. ...

Many of history's most important drivers are inter-subjective: law, money, gods, nations.

That last list looks familiar. Gods and prices are not features of the wavefunction of the physical universe--they're features of communication networks, or cultures. The creation of a third, explicitly defined category (phrases that mean similar things are "social construct" and "myth," at least when used non-pejoratively) solves the epistemic crisis of realizing that many, if not most, of the interesting things in life are neither objective nor subjective. The rules of association football are not objective natural laws baked into the universe before there was time, but neither can they be changed by a single person deciding to play differently. (Many authors fall headlong into this epistemic crisis, and Harari every now and then seems to have his presentation, if not his arguments, tripped up by it. But on the whole he manages it well.)

Harari gives the standard history of humans from about 70kya to about 12kya; Sapiens spread out of Africa, decimating and replacing many populations in the way, including both megafauna and other humans. Some managed to contribute genes to modern Sapiens, like Neanderthals, but this is likely cold comfort to animals, peoples, and cultures buried by rivals that were not individually stronger, but more suited to large-scale conflicts.

The Agricultural Revolution

Harari also gives the standard history of the start of agriculture: it seems to have been individually unpleasant but collectively empowering. This is one of the major trends that Harari identifies--the path of history is that stronger collectives absorb or destroy weaker collectives. Much like Dawkins called his account of evolution The Selfish Gene to make obvious that his conception of evolution centered on genes instead of on individuals, one might call this account of history The Selfish Culture to make obvious that this conception of history centers on cultures instead of on individuals. (Contrast with Yvain's article centered on individuals.) Harari states this late in the book:

history's choices are not made for the benefit of humans. There is absolutely no proof that human well-being inevitably improves as history rolls along. There is no proof that cultures that are beneficial to humans must inexorably succeed and spread, while less beneficial cultures must disappear.

And so viewed from Mars, the story of history after agriculture is the story of collectives trading off individual satisfaction for collective power time and time again. Since collective power is what determines survival of a culture, we are left with an immensely strong culture that holds the entire world in its grasp--but, to the individual people living in it, may not actually be any more satisfying than life as a nomad. When we broaden our view to other organisms, domesticated and wild animals make the story even more clear and extreme. Industrially managed cattle are more 'collectively powerful' (in the sense of being economically useful to Sapiens) than wild aurochs herds, but by almost any scale their lives are tremendously miserable compared to their undomesticated ancestors. Sapiens today are not quite industrially managed and only partially domesticated, but potential futures where there is more management and more domestication strike most moderns with horror. 

The Unification of Humankind

The ability to reason about inter-subjective objects allows humans to scale their cooperating collectives; larger collectives have more power, intelligence, and investments, which allows them more control over the physical world. This control is reinvested, and the trend of increasing collective power continues. This period of history marks the transition from many independent and mostly unconnected collectives of humans into one connected collective.

Over the millennia, small simple cultures gradually coalesce into bigger and more complex civilisations, so that the world contains fewer and fewer mega-cultures, each of which is bigger and more complex.

The default behavior of all social animals is to divide the world into "us" and "them," and what is remarkable about Sapiens is the capacity to enlarge the "us" to include more and more power (and individuals). The three trends Harari identifies leading to more unification:

The first millennium BC witnessed the appearance of three potentially universal orders, whose devotees could for the first time imagine the entire world and the entire human race as a single unit governed by a single set of laws. Everyone was 'us', at least potentially. There was no longer 'them'. The first universal order to appear was economic: the monetary order. The second universal order was political: the imperial order. The third universal order was religious: the order of universal religions such as Buddhism, Christianity, and Islam.

Merchants, conquerors, and prophets were the first people who managed to transcend the binary evolutionary division, 'us vs them', and to foresee the potential unity of humankind. For the merchants, the entire world was a single market and all humans were potential customers. The tried to establish an economic order that would apply to all, everywhere. For the conquerors, the entire world was a single empire and all humans were potential subjects, and for the prophets, the entire world held a single truth and all humans were potential believers. They too tried to establish an order that would be applicable for everyone everywhere.

I won't go through the details of Harari's history of how those three forces worked to bring collectives together. Instead, I'll just share the passages I highlighted from those chapters:

Christians and Muslims who could not agree on religious beliefs could nevertheless agree on a monetary belief, because whereas religion asks us to believe in something, money asks us to believe that other people believe in something.

For thousands of years, philosophers, thinkers, and prophets have besmirched money and called it the root of all evil. Be that as it may, money is also the apogee of human tolerance.

The Chinese Mandate of Heaven was given by Heaven to solve the problems of humankind. The modern Mandate of Heaven will be given by humankind to solve the problems of heaven, such as the hole in the ozone layer and the accumulation of green-house gases. The colour of the global empire may well be green.

When animism was the dominant belief system, human norms and values had to take into consideration the outlook and interests of a multitude of other beings, such as animals, plants, faeries, and ghosts.

(Consider Gwern's article on The Narrowing Circle.)

Harari discusses two philosophical problems that religions suggest answers for: order and evil. It is perhaps surprising that we live in a universe that seems mechanical and orderly, with universal laws closely related to fairly simple mathematics. It is also perhaps surprising that we live in a universe with tremendous amounts of suffering and wickedness.

So, monotheism explains order, but is mystified by evil. Dualism explains evil, but is puzzled by order. There is one logical way of solving the riddle: to argue that there is a single omnipotent God who created the entire universe - and He's evil. But nobody in history has had the stomach for such a belief.

That no one can stomach it is not quite true, especially if one lets "evil" include indifference. Lovecraft's Cosmicism seems to fit, and Moloch and Gnon both seem to fit. The most heartening version is the "dualism" that sees the mathematics behind the universe as fundamentally uncaring, indifferent, and omnipotent, and humans and human culture as the force of caring, growing in power and strength. One might unite behind the humanist Ahura Mazda against the mathematical Angra Mainyu; one probably won't unite over identification of evolution with Azathoth.

One can see that as an example of what Harari identifies as the dominant religion of the day, "humanism," which he splits into three broad sects:

Today, the most important humanist sect is liberal humanism, which believes that 'humanity' is a quality of individual humans, and that the liberty of individuals is therefore sacrosanct. According to liberals, the sacred nature of humanity resides within each and every individual Homo sapiens. The inner core of individual humans gives meaning to the world, and is the source for all ethical and political authority. If we encounter an ethical or political dilemma, we should look inside and listen to our inner voice - the voice of humanity. The chief commandments of liberal humanism are meant to protect the liberty of this inner voice against intrusion or harm. These commandments are collectively known as 'human rights'. ...

The liberal belief in the free and sacred nature of each individual is a direct legacy of the traditional Christian belief in the free and eternal souls. Without recourse to eternal souls and a Creator God, it becomes embarrassingly difficult for liberals to explain what is so special about individual Sapiens.

Another important sect is socialist humanism. Socialists believe that 'humanity' is a collective rather than individualistic. They hold as sacred not the inner voice of each individual, but the species Homo sapiens as a whole. Whereas liberal humanism seeks as much freedom as possible for individual humans, socialist humanism seeks equality between all humans. According to socialists, inequality is the worst blasphemy against the sanctity of humanity, because it privileges peripheral qualities of humans over their universal essence. For example, when the rich are privileged over the poor, it means that we value money more than the universal essence of all humans, which is the same for rich and poor alike.

Like liberal humanism, socialist humanism is built on monotheist foundations. The idea that all humans are equal is a revamped version of the monotheist conviction that all souls are equal before God. The only humanist sect that has actually broken loose from traditional monotheism is evolutionary humanism, whose most famous representatives are the Nazis. What distinguished the Nazis from other humanist sects was a different definition of 'humanity', one deeply influenced by the theory of evolution. In contrast to the other humanists, the Nazis believed that humankind is not something universal and eternal, but rather a mutable species that can evolve or degenerate. Man can evolve into superman, or degenerate into a subhuman. 

The Scientific Revolution

Harari identifies the scientific revolution as a feedback loop between research, power, and resources that led to runaway growth. But 'research' is as old as the cognitive revolution, in the sense that there have always been scholars of one form or another. The three differences underlying the Scientific Revolution were the willingness to admit ignorance, the centrality of observation and mathematics, and the acquisition of new powers.

No rationalist will be surprised by the importance of ignorance, uncertainty, and curiosity. No empiricist will be surprised by the centrality of observation (while the necessity of math remains potentially puzzling). And unless it led to the acquisition of additional powers in the realms of physics, chemistry, or biology, it seems unlikely that the Scientific Revolution would be an epoch of history, rather than just a philosophical curiosity.

The Scientific Revolution has not been a revolution of knowledge. It has been above all a revolution of ignorance. The great discovery that launched the Scientific Revolution was the discovery that humans do not know the answers to their most important questions.

The description of previous eras centers on what Eliezer calls a "mere Ultimate Prophet." Either an individual person doesn't know something (but could learn it by studying the prophets / ancients), or that thing is unimportant, or it is important and this new prophet can explain it. Acceptance of ignorance on the important questions leads to observation on the important questions, and more importantly a sustained community of observations. Instead of taking a single observation and centering a community around that answer ('eating an apple a day will extend your life'), a community can be centered around a question ('what behaviors extend lives?').

Modern-day science is a unique tradition of knowledge, inasmuch as it openly admits collective ignorance regarding the most important questions. Darwin never argued that he was 'The Seal of the Biologists', and that he had solved the riddle of life once and for all. After centuries of extensive scientific research, biologists admit that they still don't have any good explanation for how brains produce consciousness.

The willingness to admit ignorance has made modern science more dynamic, supple, and inquisitive than any previous tradition of knowledge. This has hugely expanded our capacity to understand how the world works and our ability to invent new technologies.

As science began to solve one unsolvable problem after another, many became convinced that humankind could overcome any and every problem by acquiring and applying new knowledge. Poverty, sickness, wars, famines, old age and death itself were not the inevitable fate of humankind. They were simply the fruits of our ignorance.

A critical part of the feedback loop, of course, is resources. Research is funded by governments, corporations, and individuals because they expect to see some political, economic, or religious good from that research. Progress is not in every direction or a random direction; it is in a direction determined by the values of the funders of research.

The book ends with a description of transhumanism. With power and intelligence comes the ability to design, and historically we have mostly thought about designing our environments. The organisms around us were inherited and partially designed, but we can see a time when farm animals are designed like farm machinery, and even intelligences like ourselves are intelligently designed. But Harari is no techno-optimist who assumes that everything will turn out well; if anything, he draws the trendline towards dystopia. He recognizes the value problem as perhaps the most important issue of the near future.

But, much like Robin Hanson thinking that Ems will lead lives they consider worthwhile, Harari spends about a chapter pointing out that we live in a dystopia relative to our ancestors, alienated from many deep relationships that they would have trouble imagining a worthwhile life without. It looks to me like Harari identifies Moloch as a major force of history, and retaining the View From Mars, does not see a point in extolling its virtues or condemning it, asking what will happen instead of what should happen, and pointing out that we should think long and hard about what should happen, and how to turn that into what will happen.

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The other book that I've read that I think this is most similar to is Why The West Rules--for Now by Ian Morris (some discussion on LW here). Both are written by historians, both start their description of the universe 13 billion years ago, and both conclude with transhumanist predictions that the story of the universe from 2050 onwards will differ from the story beforehand in deep and meaningful ways. (Morris makes the claim that the two possibilities are "singularity" and "collapse," with "business as usual"--how most people expect the future to go--being entirely unreasonable on historical grounds.)

But while I just thought Morris's book was neat as an independent summary and confirmation of this view of history, I thought Harari's book was important enough to write up this article because Sapiens seems to have much crisper abstractions, more developed causal relationships, and more focus on the non-material aspects of historical changes. (It's also shorter, at about 460 pages instead of about 700, which puts it at a length such that I can recommend it more easily.)

Overall, the book is remarkably even-handed and broad, which is difficult when talking about the possibilities of the future, including the values that we might take on. The parts I found weakest were when the I thought the View From Mars slipped, though that may be personal taste (and none of the points seemed egregious enough to quote and attack). I want to say it's the best introduction I've come across to this perspective of history and the future and the underlying trends and principles that unite them--but, really, what I mean it's the most compact and readable presentation of them. Whether or not it actually functions as an introduction is something I'm too deep into this view to evaluate (but, once I've subjected my parents to the book, will probably be more able to determine).

Who should read it? I found it interesting, despite having come across most of its component claims before. I suspect that anyone who wants to think deeply about Moloch, values, or the project of socially determining values would benefit from reading the book, if just to see how other branches of thinkers are thinking about these issues. I suspect most people would benefit from reading about early human history at least once, and if you've haven't this is probably a treatment more suited to the interests of LWers than others.