Three great eigenmodes

Societies have existed so far in three basic eigenmodes. (Some might argue for a fourth eigenmode; see below.)

I have described two of these eigenmodes already: hunter-gatherers such as the San, and cities such as New York. The third eigenmode is intermediate between these two. It consists of societies whose members grow their own food and live in isolated settlements with no formal governmental structures.

Let us characterise these eigenmodes more closely...

Family-level	Example: San Size of typical community: 10 people Political mechanisms: Egalitarian; no formal leaders (elders may be respected). Those who try to 'act big' are mocked and resented. Friction/conflict is resolved by one party moving away to join friends, relatives or in-laws in another group (or by violence). Economic mechanisms: Foraging (living off the land); nomadic; very simple equipment. Philosophy of share-and-share alike. Intricate customs give members rights to specific parts of the day's catch. Those who do not 'pull their weight' are subject to teasing and gossip, but there is no explicit reckoning of debits and credits. Social identity: Each family-level group considers itself part of a tribe of several hundred people, coming together a few times per year.
Village-level	Example: New Guinea highlands Size of typical community: 1000 people Political mechanisms: 'Big men' attain prestige through ability, hard work, accumulating wealth and careful cultivation of social networks. They wield influence not formal power. Disputes lead to feuds, where a man allies with his brother against his cousin, and with his cousin against a more distant relative. Big men or priests mediate to break the spiral of violence. Economic mechanisms: People farm/garden. They help each other, e.g. in harvesting/housebuilding, but debts must be repaid (perhaps many years later). Elaborate displays of generosity gain prestige. People are self-sufficient and specialisation is rudimentary. Social identity: Kinship (degree of relatedness) dictates people's obligations and behaviour towards each other.
City-level	Example: New York Size of typical community: 100,000+ people Political mechanisms: Leaders exert formal power, promulgating laws and enforcing them via police and law courts. The position of leader and the hierarchy of officials are permanent, though the individuals fulfilling these roles may change. Economic mechanisms: People are specialists and must exchange with others to obtain the necessities and luxuries of life. These exchanges are commercial transactions, in which there is an explicit and immediate balancing of value. The political authority demands a share of economic output (tax), to spend on public goods like defence, roads and social security. Social identity: People can be themselves; this contrasts with other modes, where everyone knows everyone else's business, family and background.

If you brought some ancient Romans to modern New York and asked them to buy a bottle of win in a shop, then, apart from the language issue, they would understand exactly what was involved. They would be familiar with shops and money. They would also recognise other aspects of the city such as street signs, public and private buildings, and even wheeled vehicles (though they might be surprised at these being self-propelled).

By contrast, if you brought to New York some people who had lived all their lives in an isolated New Guinea village and asked them to buy wine in a shop, they would have little idea what you were talking about. They would find the whole environment of the city unfamiliar and bewildering.

(Nevertheless, a New Guinea highlander might be at home with particular pieces of technology, such as a transistor radio, where the Roman would not have a clue, so this is not an issue of mental capacity.)

This reflects the fact that the ancient Romans, though they lived two millennia ago, were in the same social eigenmode as modern city-dwellers, whereas the inhabitants of a 21st century village cut off in the highlands of New Guinea, are in a different eigenmode.

Some might say that there should be an intermediate eigenmode, that of the 'chiefdom', between the village and the city. A chief's authority is more permanent and formal than that of the village big man, but less formal than that of a city government. For example, the chief collects tribute, unlike a big man, but this falls short of a proper taxation system. However...

• While the chiefdom is indeed distinctive, the existence of three basic eigenmodes can nevertheless be accounted for by factors that I will explain shortly (in another post). I therefore prefer to see chiefdoms as eigenmode "2½" (with the village as 2 and the city as 3).
• Although there are three basic eigenmodes, there may be many variations on them. A Roman city has its basic features in common with a modern city, but in detail obviously there are differences. Both are eigenmodes in the sense of being self-consistent solutions to the problems of social living. However, in comparison with Rome, the modern city solves the problems with more extensive economic specialisation, more effective policing, higher population density, and a greater ratio of urban to rural population.

It remains a valid question whether there can be a fourth eigenmode beyond the three outlined above, i.e. one that has not yet been realised. I believe the answer may be yes, but I need to discuss other things before I can talk about this properly.

Eigenmodes

In my last post I talked about the lifestyles of New Yorkers or San hunter-gatherers as being each a self-consistent solution to the problems of social living.

I call such a self-consistent way of life a social eigenmode.

'Eigen', from the German, means 'characteristic'. An eigenmode is therefore a characteristic mode of social living, i.e. one that is feasible/allowable as opposed to impossible/inconsistent. (This use of the prefix is derived from mathematics. An eigenvector of a matrix is a vector whose direction does not change after multiplication by that matrix; in this sense the vector is characteristic of the matrix.)

Let us put this symbolically.

Suppose a society's way of life (mode) is designated by M, which includes technology, population density, customs and everything else that describes how the society's members live.

Such a society is then exposed to the problems of social living, e.g. obtaining sustenance, caring for the young, resolving disputes and so on. These problems challenge or 'act on' the society's mode of existence. Let us represent this by P(M).

If the society's way of life is not a successful solution to the problems of social living, the society will necessarily change to a different way of life, say to M'. Let us write this as P(M) -> M'. If M' also does not solve the problems, the society will need to change again, say to M''. I.e. P(M') -> M''.

A social eigenmode is a value of M that satisfies the equation P(M) -> M. A mode that satisfies this equation is one that solves the problems of social living and does not need to change in response to those problems.

An eigenmode is therefore an attractor of the operator P(). [At least, if the operator P() has attractors, they will be eigenmodes.] What this means is that any given mode of existence will evolve, under repeated exposure to the problems of social life, towards one of the allowable and self-consistent eigenmodes successfully solving those problems, and there it will stay.

Societies and self-consistency

The Namibian government was recently criticised for its treatment of the San or Bushman people, hunter-gatherers living in the Kalahari Desert. It had forced them to leave the desert and give up their traditional lifestyle. According to the government, this was so that the San would undergo development and become part of mainstream Namibian society. The San and their supporters said that the government's real motive was to facilitate exploitation of the desert's mineral resources. A court case found in favour of the San, although the dispute will no doubt go on.

Kalahari San (Bushman)

There is a tendency to think of people like the Kalahari San, whose way of life is essentially that of the Upper Paleolithic, as cases of arrested development. It seems as though their society, unlike our own, has failed to progress. They appear to be living fossils, hangovers from the stone age. It may even be thought that the dark-skinned San lack the intellectual resources of the white races, whose technological civilisation now dominates the planet.

Such ideas need to be put aside...

• On the racial issue, the Sami, or Lapps, of Norway and Sweden are fair-skinned, have been hunter-gatherers in modern times and remain so, in part, to this day.
• Rather than being a hangover from the stone age, the San may have taken to their way of life in the Kalahari only a few centuries ago, fleeing from slaveraiders and European colonists.
• The San are just as keen and capable at dealing with modern technology as people belonging to western society. And the average person in western society had no more involvement in developing advanced technology than did the Bushman in the following picture.

San hunter with GPS device

Nineteenth and early twentieth century anthropologists thought in terms of a ladder of social evolution. At the bottom were 'savages' like the San. Next came 'barbarians', who farmed rather than hunted for their food but were otherwise self-sufficient with a simple lifestyle. Above these were 'chiefdoms', and finally 'states' or 'civilisations', with formal governmental structures and complex economies. Societies were presumed to progress through the successive stages.

It might be thought that this website has a similar view of 'progress'. In an earlier post I showed history as a graph of upward movement towards ever higher Kardashev levels. It is true that I consider human destiny to be mastery of the universe, and since we started from nothing there has to be a process of growth or development to get from here to there. However, we are not 'better' or 'cleverer' than stone age people (past or present). Different ways of life are sensible and successful solutions to the circumstances in which people find themselves, while the dynamic that propels societies from one to the other has a rationale of its own--it is not simply the piling up of inventions by particular brilliant individuals. We should not confuse societies with the people that live in them. The greater complexity of some societies can no more be attributed to them being composed of more capable human beings than the greater complexity of some biological organisms can be attributed to them being composed of more capable molecules.

The way of life of the San and other hunter-gatherers has a logic to it...

• Since they live off the land, the San must form small, widely-spaced groups and move regularly in pursuit of food. Most of the time, they separate into bands of no more than ten adults and roam territories hundreds of miles across over the course of a year. The San could not live in a group of 100,000 people because such a group would instantly devour any patch of berries or colony of rabbits it came across. A city-sized community of hunter-gatherers would have to move impossibly far and impossibly often in order to support itself.
• Meanwhile, since the San live in such small groups, their way of life has to be very simple. Think about all the expertise and labour that goes into building a car, or setting up a GPS network. An isolated group of ten people, however capable or intelligent, could never undertake projects of this kind. To have, say, a motor industry you need a large number of people, with some mining the raw materials, others designing and assembling the product, and still others growing the food to keep everyone alive.
• Finally, since they move around so much and carry everything with them, the San's way of life again has to be very simple. Instead of transporting a drinking beaker everywhere, for example, it is easier just to cup your hands.

Therefore, San communities must be small and mobile because they live simply. And the San must live simply because their communities are small and mobile. The two things go hand in hand.

Contrast this with the situation of New York...

• A huge, settled population like that of New York cannot live directly off the land. It has to have an elaborate economy. It needs a large number of specialists doing and making the things without which New York could not function--food retailing, plumbing, building, policing... At the same time, all the complex things that go on in New York, such as stockbroking or providing an underground train service, require the co-operation of a large, dense population.

So New York's large size goes hand in hand with its technological complexity, just as the small size of San groups goes hand in hand with their simplicity.

You cannot mix and match the characteristics of the two lifestyles.

The San lifestyle is incompatible with, say, advanced plumbing, just as the New York lifestyle is incompatible with the lack of advanced plumbing.

If for some reason New York's economy were dismantled and the population were forced to become self-sufficient hunter-gatherers, life in the city would become intolerable. The inhabitants would quickly flee the city and spread across the landscape in search of food. It would not be long before they were back to the San way of life.

Rather than thinking in terms of backwardness and advancement, we might see the San and New York lifestyles as alternative, self-consistent solutions to the problems of social living.

When we look at the San lifestyle, we should not regard it as indicating a failure of intellect or imagination but should recognise it as one of the possible ways that humans may live, whose simplicity is one of its inevitable and essential characteristics.

It might be objected that the San's lack of movement towards a more complex, 'civilised' eigenmode is a kind of backwardness. However...

• Since the San reject the town-life that the Namibian government wants to force on them and have campaigned to go back to the desert, it is clear that they prefer their desert lifestyle. They enjoy hunting and gathering, which gives them all the food they need, for a few hours work a day, while in the desert they are freer than they would be in civilised society, where they would have to obey laws and pay taxes.
• The complex lifestyle of civilisation can be seen as something that was forced on people when hunting and gathering became untenable, rather than as a product of greater cleverness. Civilised people are not necessarily better off than the San. Many still idealise and hanker for the simple, self-sufficient life. Hunting, for example, is often the prerogative of a privileged elite, while gathering, such as blackberrying, may be done for pleasure.

My main aim in this post has been to introduce the idea that all the features of a particular way of life fit together in a logical manner. As a subsidiary point, I have wanted to challenge the notion that social sophistication should be put down to the greater inventiveness of certain races accumulating over time. Rather than ranking societies on a ladder of progress, we will understand them better if we approach and explore them as individually self-consistent systems.

Outward pressure

Easter Island is a triangular speck in the Pacific Ocean, over a thousand miles from the nearest inhabited land. When it was 'discovered' by the Dutchman Jacob Roggeveen, on Easter Sunday 1722, it already had people living on it.

Humans had only been on Easter Island since about AD 1000. Nevertheless, that they had reached this remote spot points to humanity's strong centrifugal tendency. Humans were already in Australia a few thousand years after our emergence as a species, and that journey would have required a sea crossing at some point.

This shows that people do not naturally live together at high densities. They are driven, to some extent, to get away from each other. This outward pressure has several aspects:

1. For a given technology and way of life, a particular land area will support a limited number of people. As population increases, humans find it easier to move to empty land than to develop ways of supporting more people from the same territory.
2. Living together causes friction and conflict. Some people may bully others or may impose themselves on others in an effort to keep order. At least part of the population finds it preferable to move away, rather than stay and have its freedom curtailed.
3. While many humans are happy to drift along with what they know, others have a high degree of 'natural curiosity' that makes them want to explore beyond the known, both geographically and in other ways.

It is now fairly clear, based on genetic data, that humans arose in Africa recently, and spread out from there. Modern humans are therefore all quite closely related.

Nevertheless, I disagree in detail with current reconstructions of the peopling of the world (link requires Google Earth; a Google Maps version is here). According to the view presented in the preceding link, while people reached Australia about 40,000 BC, they did not reach North Africa until 20,000 BC, even though they had evolved on the African continent. Furthermore, while people had got half-way down the African coast by 40,000 BC, they supposedly did not reach the southern tip of Africa until 25,000 BC, even though they were in China and Spain by 40,000 BC and in Britain only a couple of thousand years later. Such a pattern makes little sense and rather shows the limitations of the gene-mapping methodology on which this reconstruction is based.

I suggest that, after emerging in central east Africa, the human species spread to and throughout every continent within a few thousand years, say around 40,000 BC. Only the peopling of oceanic archipelagoes that are not connected to the mainland by chains of intervisible islands did not occur until much later, say from about 5000 BC.

(Although mainstream opinion holds that humans did not move into the Americas until after about 15,000 BC, some archaeologists do place the entry into the Americas around 40,000 BC, on the basis of sites that remain controversial.)

I am still researching this issue...

Now we are awake

Clive Wearing was a musician who in the 1980s suffered an infection that destroyed his hippocampus, the part of the brain that lays down long-term memories. Thereafter Clive was unable to remember anything beyond a few minutes at a time. He lived in an eternally fleeting present, in his wife's words 'with no past to anchor it and no future to look ahead to'. As if to compensate, he maintained a diary in which he jotted down his thoughts every two or three minutes. The entries in the diary looked something like this:

10.20 Awake at last
10.23 Actually now I am awake
10.25 The above is mistaken. I am awake now!
10.28 No, no, no. NOW I am completely awake.
10.31 FINALLY WOKEN UP!!!!
10.33 Now I really am awake.
10.36 AWAKE FOR THE 1ST TIME IN YEARS
Etc. (See C Blakemore The mind machine pp. 55-8)

The human race suffers from a similar kind of amnesia. Each generation believes that it, at last, is awake, and that its parents and all the generations that went before were scarcely conscious.

This is what lies behind the belief that, until very recently, change has been minimal and only in our era has humanity achieved social and technological take-off. Previous generations are thought to have slumbered their way through lives that showed little variation from start to finish.

In my last post, I quoted a recent writer making this point. Another recent expression of it is the claim of the psychiatrist, R D Laing that "We live in a moment of history where change is so speeded up that we begin to see the present only when it is disappearing".

To show that this attitude is itself a constant of history--just as Clive Wearing constantly believed himself to be waking up--I would like to offer some quotations from earlier writers on the same topic...

Our century has more history in its hundred years than had the whole world in the previous four thousand years; more books have been published in the last century than in the five thousand years before it; for it has profited by the recent inventions of typography, cannon and the marine compass.
-- Tommaso Campanella (1568-1639)

We have raised up a truly philosophical age, in which the deepest recesses of nature are laid open, in which splendid arts, noble aids to convenient living, a supply of innumerable instruments and machines, and even the hidden secrets of our bodies are discovered; not to mention the new light daily thrown upon antiquity.
-- Gottfried Leibniz (1646-1716)

No age hath been more happy in liberty of enquiry than this.
-- Francis Bacon (1561-1626)

Whoever reads these chronicles will find that, from the birth of Christ on, the whole history of the world in these hundreds of years is unparalleled, in every way.
-- Luther (1483-1546, in 1521)

I owe all the above to Pitirim Sorokin in Social and cultural dynamics pp. 272-3. To continue...

[The pace of change today] makes my head giddy.
-- Josiah Wedgwood (1730-95)

What marvellous, stupendous accomplishments human effort has achieved.
-- Augustine of Hippo (354-430)

As for the arts and skills, both those useful for the necessities of life and those created for pleasure, they were either invented or tested by our city [Athens], who then passed them to the rest of the human race to use.
-- Isocrates (436-338 BC)

The discovery of a means to test weights by balances and scales has delivered our life from fraud...Countless numbers of machines also exist...[and] are at hand every day: mills, blacksmiths' bellows, wagons, two-wheeled vehicles, turning lathes, and other things...
-- Vitruvius (1st century AD)

Human achievements

It is usual to think of human development as being very slow until recently, when it suddenly took off. Here is a typical quote, from the British sociologist Anthony Giddens, relying on the American political scientist John H Kautsky:

...it is the 'relatively overwhelming absence of major social and economic
change' that characterizes the variant forms of society that existed across the
face of world history until some two or three centuries ago.

(Giddens The constitution of society p. 199)

When one thinks of the inventions of the last one or two hundred years--radio, the internal combustion engine, heavier-than-air flight, spaceflight, computers and the internet--it certainly looks as though many dramatic innovations have occurred in a very short time. Compared to the 30,000 years of the upper paleolithic, when people continued to live by hunting and gathering, the twentieth century seems to have been characterised by dizzying change.

One can also predict this on theoretical grounds. The more people on the planet, and the more technology there already is, the faster we might expect inventions to come.

Yet how should we measure the significance of an invention?

Which was more revolutionary: the invention of the typewriter or the invention of writing? There is a case for saying that the change from a world without writing to a world with writing was more fundamental than the mere technical improvement represented by the typewriter. The word processor is another (impressive) improvement within a long list of improvements affecting writing, such as paper, ink and moveable type, but neither it nor any of these is as revolutionary in its implications as the invention of literacy itself. The word processor is a great boon, but it is just a better way of producing letters and reports. It has not transformed society that much, if we remember that people still managed to organise such things as the Normandy landings or the Apollo programme without it.

The internet, too, could be seen as just another incremental improvement in information technology, building on the original invention of writing. In other words, in this important area of life, the really dramatic change occurred some five thousand years ago. Everything since has been by way of refinement only.

The invention of writing was revolutionary. Everything since can be seen as a technical improvement in the ability to prepare and disseminate written information.

In ancient times, people were already writing letters and books. Through letters, people could carry on conversations when they were physically separated. Through books, people became exposed to ideas and participated in a far-flung intellectual community. What are email and the world wide web but just better ways of achieving the same thing?

All we are seeing today are the latest twists in a long process of getting more information, more quickly to more people. Ever since the invention of writing, there has been almost continual improvement, both technological and institutional. For instance, communications could be improved by better transport or cheaper writing materials, and these could result from technical innovations as well as from the efforts of politicians and entrepreneurs in setting up factories and commercial networks. To give a couple of examples:

• In Roman times, communications were improved not only by the building of roads but by the cursus publicus (public mail), which was initially set up for governmental purposes but was also used by private persons. A system of relay stations, where horses were changed, allowed mail to be carried over hundreds of miles at the rate of a horse's gallop.
• In eighteenth century Britain, communications improved as tarmac and sprung carriages enhanced the speed and ease of road transport. A network of stage coaches was set up, distributing mail throughout the country.

One might also mention things like the postage stamp and the fountain pen, as well as the continuous evolution of printing since the days of Gutenburg and Caxton. A list of all the inventions and improvements that have advanced information technology would be enormous and would show that in every period, not just in recent times, people might have perceived themselves to be living amidst great changes.

An effect of the internet has been a 'democratisation' of information flow. Blogging allows anyone to publish their opinions, and through blogs we are exposed to alternative narratives beyond those of the 'mainstream media'. We need not believe everything we read, but sceptical commentary ('conspiracy theory') surrounding events such as 9/11 alerts us to possibilities that mainstream channels might wish to conceal. We can take a more intelligent view of what we are being told and it is seemingly harder for the authorities to deceive and control their populations. This feels like a revolutionary social change, but such democratisation has always been an accompaniment of improving information technology. It is said that the introduction of printing loosened the hold of the church over what was published, and helped stimulate the Christian Reformation. The first newspapers and journals in the eighteenth century would have seemed as excitingly subversive as blogs do today, and like blogging they were made possible by technological improvements, in this case to do with better printing presses and the distribution networks created by the stagecoach.

If we think of truly revolutionary inventions--those that are not just an improvement to an existing technique but stand themselves at the beginning of a long process of improvement--they might be more evenly distributed throughout history than we appreciate. Things like agriculture and metal-working were enormously transforming in their day, and unleashed tremendous potential for the future progress of the human race. How can we seriously think of the first generations to farm the land or to cast bronze and still agree with the above quotation that 'social and economic change' was 'overwhelmingly absent' until recent times.

Revolutionary, transforming innovations have occurred throughout history, and the more recent innovations are not necessarily more significant than those of the past.

If things that initially seem revolutionary like word processing and printing can be seen as incremental improvements, then what seem to us like small changes in, say, the design of stone tools might have seemed quite revolutionary when they were made. To us stone tools are just stone tools, but to people who knew nothing else subtle variations would have been important, and perhaps made as much difference to their way of life as the move from typewriters to word processing has made to the task of running a business today. In the same way, what seem to us like big changes, such as the introduction of the internal combustion engine, may seem like trivial improvements to people in the far future--yes, we have dispensed with the horse but otherwise we are still crudely travelling around in four-wheeled vehicles along streets and roads on the planet's surface. When people are zipping from galaxy to galaxy by some form of matter transportation, the difference between a motor-car and a horse-and-cart will not seem that great.

Those fundamental inventions that were made long ago, such as farming, writing and metal-working, did not come entirely out of the blue (I will deal with this in a later post). Nevertheless, insofar as their inventors had fewer models to go on than inventors do today, their achievement might be seen as all the greater. Something like the sewing needle has barely changed since it was invented 30,000 years ago. It was brought to perfection by people living in paleolithic times, and yet it remains a vital component of our technology (I thank my sister for this example).

I do not want to turn things on their head and argue that it was the stone age people who were the real innovators. What I do want to point out is that innovation and change have been part of human experience from the beginning, and the idea that things have dramatically sped up in our own time is a matter of subjective perception as much as objective fact.

Periodisation and orientation

In earlier posts, I talked about the overall history of the human race, from its beginnings forty or fifty thousand years ago to its culmination a million or so years from now. I did this so as to dispel the chronocentrism or distortion that comes from viewing history from our particular vantage point.

Since we represent the greatest level of advancement humanity has yet achieved, we tend to have a conceited view of ourselves and of our importance in history. It is common to talk of things happening in our day as 'unprecedented'. Of course, they are unprecedented, but this is an inevitable consequence of the fact that we live in the present and at the forward edge of time, as every generation has done and must do.

The people who lived two thousand years ago did not think of themselves as the ancient Romans, living in the past. They thought of themselves as the most sophisticated, technologically advanced civilisation that the world had ever seen, and that is what they were. Only now do we see them as part of history.

What we must not forget is that we, and our time, are also part of history, which started a long time ago and will continue a long time after we are gone. Once we were the future; today, for a brief moment, we are the present, where everything seems to be happening; and for the remainder of eternity we will be the past, getting deader and more ancient as time goes on.

History is a continuously unfolding saga, and we are just at the latest point of it.

Now that that point has, I hope, been made, I want to concentrate on the history that has actually happened.

We can begin by thinking in terms of the three ages--stone, bronze and iron--that were defined by the Danish archaeologist, Christian Jürgen Thomsen (1788-1865) and his Swedish pupil J J A Worsaae (1821-85). This scheme is a convenient simplification. There was no sharp transition between the various ages, and they occurred at different times in different parts of the world. People continued using stone tools during the bronze age, and they were already experimenting with iron long before the bronze age was over.

The human species emerged in the middle of an ice age, the Würm glaciation, which had then been going on for 60,000 or 70,000 years. (This was just the latest cold snap within the ice age proper, which started 40 million years ago and became more intense 3 million years ago, with repeated cycles of cooling and warming.)

The emergence of humans marks the beginning of the Upper paleolithic (paleolithic = 'old stone' [age]) . Stone tools were being made before this by sub-human hominids, but hundreds of thousands of years could go by with little change in their sophistication. The Upper paleolithic was characterised by more advanced stone-working, a shorter duration, and a process of continual improvement.

With the end of the ice age, it is conventional to recognise the beginning of a new period, the Mesolithic (middle stone age), some 30,000 years after humans emerged. This was characterised by finer stone blades, or microliths, which included arrowheads. It is mainly relevant to Europe, since Africa and the Middle East were already steaming into the Neolithic. This shows the relative arbitrariness of the division into distinct periods; we could as easily consider it a sub-stage within the paleolithic.

The Neolithic (new stone age), from 8000 BC, corresponds to the introduction of agriculture (until now, people had largely hunted and lived off the land). Cities arose in the Middle East, and, though this was still the 'stone age', copper and gold began to be worked (archaeologists sometimes speak of a separate 'Copper Age' or Chalcolithic).

The Bronze age came in from around 3500 BC, when people began mixing copper with tin or arsenic to produce bronze, this being harder and more useful than pure copper.

Finally, the Iron age came in some time after 1000 BC. In so far as hammers and cutting edges continue to be made of steel (an iron alloy known virtually from the beginning of the iron age), we can regard ourselves as in the iron age to this day.

I return to the point that this periodisation is a matter of convenience, to give us some signposts. We should not imagine that a gong rang and suddenly the stone age turned into the bronze age etc. Rather one thing led to another, and everything grew out of what had gone before. Nor should we imagine that the raw materials--stone, bronze, iron--were the be-all and end-all. It is just that these survive best in the soil and are most noticeable to archaeologists. There was also continuous development in other technologies and in the more intangible social, economic and political institutions.