Monday, 25 May 2015

Sapiens: a tale of human history

There have been several recent books that attempt to survey the whole of human history. Each one has a particular perspective. Thus Jared Diamond's Guns, Germs and Steel is a stab at how physical geography might explain why some regions of the world have made faster progress than others since the Agricultural Revolution; and Daron Acemoglu and James Robinson's Why Nations Fail is a similar project but here the emphasis is on which institutional factors enable some states to flourish more than others. These two books each have a definite thesis - a framework of opinions - that they defend in detail. The books are interesting because the authors' opinions are defended quite convincingly but they are opinions nevertheless.

I have just finished another book of the same type whose scope is even broader. It is Sapiens: A Brief History of Humankind by Yuval Noah Harari. The book covers the span of human existence from the plains of Africa through to our 21st century existence. One thing I like very much is that this tale is not presented as a tale of progress or advancement; it is told much more neutrally, sometimes almost as though by an observer from some distant star system. In this post I cannot do justice to every chapter but I will highlight only some of the viewpoints that impressed me the most.

In the first chapter the early origins of the Sapiens species are discussed. Since 2010 there has been a controversy about the biological relationship between that species and other human species such as Neanderthals and Denisovans. To review that controversy let me remind you that 100,000 years ago there were several species of the genus Homo alive on earth. They were the descendants of a migration of ape-like ancestors around 2 Million years ago who spread from Africa around the planet evolving into separate species such as Homo Neanderthalenis, Homo Soloensis, Homo Floresiensis, Homo Denisova and Homo Sapiens (the latter species evolving in Africa about 150,000 years ago).

Until 2010 it had been thought that, when Sapiens left Africa around 70,000 years ago to spread throughout the world, they displaced (peacably or forcibly) all other hominid species; there was no interbreeding as the species were too genetically dissimilar. So, according to this theory, all members of Homo Sapiens are pure descendants of African ancestors of 70,000 years ago and, in particular, we are all genetically alike.

However, in 2010, it was discovered that modern humans in Europe and the Middle East had about 1.4% of their DNA of Neanderthal origin; and a few months later it was discovered that up to 6% of Melanesian and Australian aboriginal DNA was of Denisovan origin. This is a major and very recent discovery and I would think that it might be wise to await confirmation before accepting it fully. However, if confirmed, a rather different picture is painted. The theory now would be that, when Sapiens met Neanderthalenis and until around 50,000 years ago, Sapiens and Neanderthalensis were genetically sufficiently close for interbreeding to occur (and similarly for interbreeding of Sapiens and other hominid species). In other words Sapiens has much more genetic diversity than had been thought previously.

This controversy is not purely a scientific one because the interbreeding side of it offers ammunition to those who would use it to promote discrimination on the grounds of DNA differences. Whether this will happen yet remains to be seen. Harari does not pursue this question - an early indicator that he is more interested in presenting a factual narrative uncontaminated by value judgements.

The next few chapters of the book are about that long period between the birth of the Sapiens species and the Agricultural revolution. We have very little to go on but we can make some plausible assumptions. Perhaps the major thing to explain is how Sapiens went from being a minor player at the beginning of that period to becoming a creature that was near the top of the food chain at the end. All other hominids had disappeared together with many of the largest animals - and we can correlate quite well their disappearance with the moment they first came into contact with Sapiens so it is reasonable to believe that Sapiens was becoming more and more formidable. From what source were these powers derived?

While confessing that there are no certainties Harari advances some interesting explanations. They are all cognitive and the idea I found the most interesting was the idea that only Homo Sapiens was capable of inventing myths. The word 'myth' for me used to mean an unfounded belief, or a story, about something fanciful. But Harari uses it in a wider sense. For him a myth is any concept about something that has no objective existence (and it carries no negative connotation despite that - myths are simply ideas).

He makes it plain by an example - the Peugot example - of how general a meaning the word 'myth' has.  Small groups of individuals can act cohesively on an enterprise by everyone being able to communicate with everyone else. Clearly this won't work for larger groups. Larger groups need to be unified behind a myth, some shared belief that binds them together. A nation state can only operate because its members share the myth of national identity. A legal system can only operate because its members believe in the system of laws, justice and human rights it promotes and defends. A motor company, such as Peugot, binds its employers together because they all believe in the myth of limited liability companies. And national identities, the idea of justice, the notion of a limited liability company really are myths in that none of these things would continue to exist if the minds of the believers all perished in an instant.

This general idea of myth surfaces several times later in the book. One can raise a philosophical objection depending on how Platonic a frame of mind one is in. Is it really the case that 'Justice' is no more than a belief or does it have some "real" aspect? Once upon a time I, as a practising Pure Mathematician, would have been quite susceptible to strong mathematical Platonism. Now I am not so sure; as I have retreated from the subject so has my conviction that mathematical notions have an independent reality. In any case I found myself very persuaded that for non-mathematical thought objects there was really no case that they had an independent existence. The French Revolutionaries all believed in Liberté, Egalité, Fraternité and Americans believe in 'American exceptionalism'; but there's no objective reality to these terms - they are myths.

Once one renounces the Platonic inclination that these myths do have an objective reality a lot of contradictions disappear. Liberals like the ideas of equality and freedom. But they are contradictory (and, in a stroke, we see why politicians are always fighting). If you champion equality you must place checks on individual freedom - otherwise people would be free to trample on their equals. We don't need myths to be consistent - but we do want our Physics to be consistent!

The next tranche of chapters in the book concerns the period from the Agricultural Revolution through to the Enlightenment. This period began between 10,000 and 15,000 years ago. It is far too short a time for any significant gain in the raw power of Sapiens by way of natural evolution. Yet since number of changes in that time to the way Sapiens live far outnumbers those occurring in the previous 100,000 years (I will return to the post-Enlightenment changes later).  What happened?

Harari points out that the change from the hunter-gatherer life-style to that of a permanent small communities centred around farming was possibly a change for the worse for most people. The hours were long and diseases caught from farm animals were usually mortal. But the ability to have reliable and abundant food allowed a rapid increase in population; unfortunately the benefits of more abundant food would have been counter-balanced by the need to feed a larger number of people.

The Agricultural Revolution is ostensibly about how Sapiens domesticated their food sources, the most extensive food source being wheat. Harari offers an opposite perspective: that wheat domesticated us! It's a compelling point of view. Wheat the grass that once grew only in the East has spread throughout the world, spreading its genes far and wide, and become one of the most successful life-forms ever. It has done it by having Sapiens creatures in their millions tend to its health, prepare stone-free soil for it to grow strong, defend it from disease, fetch and carry water for it from dawn to dusk, and build fenced areas to keep it safe from predators.

Once Sapiens began to live in agricultural communities myths were needed to keep them from fragmenting. Some of these were religious: serving the gods of the seasons and the spirits that protected animal and food sources was vital and rituals grew up to bind people to a common purpose. But other myths became important as communities grew in size. Legal codes such as that devised by Hammurabi depend on myths: the notion that rights and wrongs were absolutes is mythical. If you feel uneasy about that just think how opinions have changed over the treatment of those members of Sapiens who have two X-chromosones. Nations states are sustained by myths: seriously, would you voluntarily die to defend the 'honour' of your country?

But if the pace of change picked up after the Agricultural Revolution it became a frenetic Scherzo once the Scientific Revolution got underway. This is the subject of the third quarter of the book. Since this occurred within historical times we know much more about what triggered this second revolution (sometimes called the Enlightenment but this term emphasises the questioning and rejection of religious authority more than the discoveries made by the new scientific method).

Harari gives a lot of attention to a new practice that began to pervade learned society: the free admission of ignorance: 'ignoramus' was less and less a term of opprobrium. He points out that ancient traditions recognised two kinds of ignorance. An individual might be ignorant of something important (where did human beings come from? - ask the priest) or an entire society might be ignorant of something apparently unimportant (how do spiders weave their webs? - it matters not because God knows). But eventually it dawned on certain thinkers that there were important things that the entire society might not know and so they had to find these things out for themselves. This turned out to be possible by adopting what we now know as the scientific method: systematic observation, gathering data, forming hypotheses, testing these hypotheses. Amazingly this worked and after a few hundred years of it we can look back and compare the knowledge so acquired since 1500AD with the knowledge acquired in the previous 150,000 years - it is an astonishing comparison.

The Scientific Revolution had many knock-on effects. One such effect which I had not previously considered until Harari highlighted it is the rise of capitalism. Capitalism is characterised by investing the profits of an enterprise rather than blowing it all on war or good living. When it began to be apparent that scientific discoveries often gave advantages to a society it became necessary to finance the work of scientists. Thus when James Cook sailed to claim new territories for the English King he took with him men who had no military skill at all: their purpose was to collect more knowledge to further science. Harari very skillfully describes how from these humble origins our capitalist societies grew into the behemoths we see today. And, as usual, he describes these societies without giving value judgements.

So, if there was one thing that really impressed me about the author it was his ability to keep his opinions out of the narrative. As he might himself say: my opinions are myths - they will vanish when I die. This lack of polemic is actually rather a good technique for persuading his readers. It does not back them into corners and they can come to their own conclusions about which aspects of Sapiens culture they are comfortable with and which they abhor. For example, I myself found his laconic description of how Sapiens has enslaved other animals as food sources all the more compelling because it was so muted.

There is much in the book that I haven't mentioned, particularly about modern societies. It is a tour de force as well as being a fascinating read and I strongly recommend it. As a general guide to the book I give below its detailed Table of Contents.
  1. Cognitive revolution
    1. An animal of no significance
    2. The tree of knowledge
    3. A day in the life of Adam and Eve
    4. The flood
  2. Agricultural revolution
    1. History's biggest fraud
    2. Building pyramids
    3. Memory overload
    4. There is no justice in history
  3. Unification of humankind
    1. The arrow of history
    2. The scent of money
    3. Imperial visions
    4. The law of religion
    5. The secret of success
  4. Scientific revolution
    1. The discovery of ignorance
    2. The marriage of science and empire
    3. The capitalist creed
    4. A permanent revolution
    5. And they lived happily ever after
    6. The end of Homo Sapiens