Most past and many present societies would be unable to distinguish where work ends and the rest of life begins. Certainly, that Monday morning feeling would not have meant much to our ancient ancestors, constantly on the move scavenging for food. Nor did it affect the farming communities that predominated in most of the world until the past couple of centuries.
What they did and when and where they did it was dictated by the seasons, the availability of light and, for most of that time, basic personal needs.
Colleagues were family and neighbours, and men and women worked as soon as they were old enough to contribute and stayed working until they died. The idea of work as something distinct from simply existence is a relatively modern concept.
The only characteristic of work that appears to have remained consistent is that it is something many people would rather not do. After all, according to the Bible, it was to punish Adam for disobeying him that God cursed the ground so that "In toil you shall eat of it all the days of your life" and "In the sweat of your face you shall eat bread".
In the 17th century Sir Dudley North wrote: "It is incident to the true nature of work not to delight in it." And for Samuel Johnson: "Every man is, or hopes to be, an Idler." This helps explain why activities such as hunting, fighting and food shopping can be work in one context and leisure in another, and why what one person regards as work, another sees as hobby.
Early English colonists accused Native Americans of being idle because they were warriors and hunters rather than farm workers.
Today, people pursue activities for pleasure that others do merely to pay the mortgage - something especially true in creative fields; it is only in the modern age that intellectual labour has been regarded as work at all.
While it remains uncool to admit to enjoying work, a recent study by the Work Foundation found that two-thirds of respondents were satisfied or fairly satisfied with their jobs. It also identified two million people in the UK who loved their work so much they said they wanted to do little else.
While it may be difficult to define work, it is work that helps define us as human. Although other species do use tools, the ability to make them has long been considered a human characteristic. Thanks to the long infancy of our young and their inability to cling to a mother who is off scavenging, we are also the only primates to have specific places where females and their young stay and where males bring back the food they find. Evidence of both tool-making and what historian John Roberts calls the "home base" dates back two and a half million years to the Olduvai Gorge in Tanzania.
However, the hunter-gatherer existence persisted for many more thousands of years until small nomadic groups first began to settle and farm land in the Near East about 10,000 years ago.
While specialist skills were useful in hunting and tool-making, it was settlement and the production of food that was surplus to the needs of individuals and their immediate families that really allowed specialisation to develop - in everything from grain cultivation to art. It also introduced the notion of private property, material wealth and social and cultural divisions.
This was where another characteristic long associated with work comes in: doing something for somebody else. Struggles between different settlements and the wars and conquests that followed, as well as different levels of skills and the power and property that went with them, made slavery a feature of most early civilisations. It persisted in many different guises across the world for centuries, from Babylon to ancient Greece, where Aristotle suggested some men were by nature slaves, and from the Slavs in early Russia - thought to have given slavery its name - to the serfs of medieval Europe.
While slaves performed functions ranging from administrators to doctors and prostitutes, most were tied in some way to the land, because that is where most work was carried out. This began to change in medieval Europe through a combination of labour shortage, due to war and famine, technological innovation, the expansion of trade, and beginnings of globalisation.
Slowly, work stopped being something carried out mainly within a household unit, with master, family and serfs working alongside one another at home or on the land. Instead, master craftsmen evolved into entrepreneurs, responsible for a team of workers and more concerned with selling the finished product than making it.
Serfs evolved into labourers and were able to demand payment from various competing employers for their particular skill. With these changes came disputes about wages and working hours, and with that came the beginning of trades unions in the form of craft guilds.
Working conditions really became issues with the factories that followed industrialisation in 19th-century Europe. It was then that work was first related to fixed hours for fixed payments and expected productivity, as well as with profits that directly benefited a single employer rather than those doing the work.
The movement of work to the factories and away from the home also highlighted problems with the employment of women and children. Divisions, and therefore inequalities, between men and women at work predate those between any other sections of society. However, when work was multi-skilled, home-based and mainly carried out for the direct benefit of the household, men and women tended to operate more as co-workers.
In the 19th century, new machines and factories destroyed the cottage industries in which many women were employed. Instead they became farm or factory hands or took sole responsibility for care of the home. Some also became "ladies" who were expected, as a sign of social standing, to do as little as possible other than read poetry and dance. Florence Nightingale described how this could lead to frustration: "The accumulation of nervous energy, which has had nothing to do during the day, makes them feel every night, when they go to bed, as if they were going mad."
Children had also always been involved in working for the benefit of the household. The writer Daniel Defoe (1660-1731) noted in the clothing manufacturing region of West Riding: "Hardly anything above four years old but its hands were sufficient for its support."
However, the slow initiation to working life, as children began to labour alongside their families in the fields or at home, gave way in the 19th century to a sudden fixed working day of 12 hours or more in a factory or coal mine. Often child workers were especially prized because their small hands were considered more dextrous, and their size meant they could reach otherwise inaccessible areas of mines or chimneys. It was only in 1875 that use of child sweeps - rare outside the UK - was outlawed.
One mill owner, Robert Owen, consciously used his New Lanark Mills to try to improve the welfare of the working classes and urged the state to take up his ideas, which included setting up a school for children under the age of 10. In 1847, parliament introduced the Ten Hours Bill, limiting the daily work of women and youths in textile factories, and this was later extended to other industries. It effectively limited everyone's working day, since the men could not usually continue their jobs without the women's input.
This was the first legislation to limit working hours, although not the first time a restriction had been considered. The ancient Greeks felt six hours were about right for a working day - a period of time echoed in Sir Thomas More's Utopia, written in the 16th century. More's ideal described men taking turns at different kinds of work, which they finished in six hours, leaving plenty of time for personal interests.
Recent moves to limit working hours have not been quite so generous. Recent European Union legislation set a limit of a 56-hour week, and even France's controversial restriction on the working week still only limits it to 35 hours, and has recently been amended to allow for overtime. Britons work about 100 hours a year more than other Europeans, although last year average hours worked did fall by an hour a week. Americans work 200 hours a year more than us. One benefit cited by those arguing for limits on working hours is a reduction of unemployment. This is a concept that only arrived with industrialisation. While people had been without work before, specialisation and the concentration of labour in towns meant that unemployment became a recognisable state and the unemployed a social problem.
In the early 1990s, an American commentator, Jeremy Rifkin, estimated that globally more than 800 million people were unemployed or underemployed - the highest level since the 1930s Depression. In a book called The End of Work, he predicted that software technologies would lead to a near workerless world by the early decades of this century and that by 2050 less than 5 per cent of the population would be needed to produce all the goods and basic services required by the human race. For him the answer was creating a "third sector" civil society based on volunteering and human relationships.
None of this seems to be happening quite how Rifkin envisaged, although he did not get everything wrong. Traditional jobs are certainly under threat, not only from new technology, but also from newly industrialised countries.
China now has 800 million workers earning a dollar a day and millions of Chinese are on the move from rural areas to the cities. There is no way Western economies can compete with China or India in terms of labour costs.
Instead, the emphasis has turned to developing "knowledge economies" - highly skilled workforces that are able to churn out a constant supply of ideas for manufacturing and marketing new products that can then be made elsewhere.
It also seems that Rifkin was right about the future lying in human relationships. Nick Isles, associate director of the Work Foundation, says business success in the future will depend not only on a well-qualified population, but also on being able to interact successfully with customers.
Managers need to put more into frontline staff with all the human skills of approachability and adaptability that computers lack.Having a more sophisticated workforce of this kind also means being nicer to them, hence current trends towards giving employees more autonomy and being more flexible about when and where they work. In April 2003 new legislation came into force in the UK allowing parents with children under six years old and those with disabled children the right to apply for flexible working. This is something which can also be attractive to employers who need to meet the demands of a 24-hour culture.
In addition, there is evidence that today's employees also want to be nicer to society in general. A recent survey by Common Purpose, which develops leadership programmes, found that nearly 90 per cent of employees were looking for careers that would add purpose to their lives, and more than a quarter said their firm was not as ethical as they would like it to be.
In a number of ways, the history of work has come full circle. Thanks to new technology, more and more people are working at home and working for themselves; numbers of self-employed in Britain increased by more than 100,000 last year.
There is new emphasis on multi-skilling and on the "portfolio career", made up of a number of different jobs, as described by business guru Charles Handy. Transitions into and out of work are also becoming less stark, with education, often on a part-time basis, continuing for many into their twenties and beyond. Retirement is also coming later for many and often through a slow reduction in hours.
As more people expect and demand to enjoy their work, and to pursue it around the clock, it is again becoming difficult to distinguish exactly when it stops.
* The Work Foundation www.theworkfoundation.com
Common Purpose www.commonpurpose.org.uk
In the past
Early classical civilisations regarded work as something that had to be done but that got in the way of the pursuit of virtue, which was why it was best left to slaves. However, work and virtue have been linked ever since Adam's expulsion from the Garden of Eden. For the early Judeo Christian tradition, it made work harder - something that continued into the 6th century when Benedictine monks, following a strict regime of mental and physical work and prayer, regarded manual labour as penance.
Medieval theologians stressed the social and moral benefits of work, although it was still not valued for its own sake, but viewed as part of the organisation of human society ordered by God. It was important for avoiding idleness which led to sin. They also taught that it was sinful for people to look for work other than that passed on from father to son.
It was the Reformation and Martin Luther in the 16th century that really started what we now recognise as the work ethic. Luther believed that people could serve God through their work, whatever it was, making manual labour as important as any other. His ideas agreed with those of John Calvin, who taught that work was the will of God, that everyone must do it and that there was no harm in looking for a job best suited to your skills or in making profits, provided that it was ploughed back into society for further improvements. This is why capitalism has often been linked with Protestantism.
When Protestants who were fleeing the turbulent religious atmosphere of post-Reformation Europe arrived in America they brought the work ethic with them. This was especially handy as the conditions they faced in setting up a new society demanded hard work. This attitude persists in the long-hours culture of modern-day America and much of the rest of the world, although nowadays it is often related to valuing work for its own sake rather than for any virtuous link.
Into the future
Forget ambitions to become a car dealer or insurance broker - both careers, along with those of estate agents, farmers, milkmen, postmen, printers and telephone operators are predicted to suffer heavy job losses by 2010, due to technology and changing social patterns. Where they do survive, they are likely to demand new skills. For example, instead of postal workers delivering letters, they are likely to use information technology to organise specialist courier services.
Today's students should be thinking about becoming time consultants, either auditing how people use their time or providing services for those who do not have enough of it - booking holidays and organising repair s.
Research carried out for City and Guilds, the UK's leading awarding body for work-related vocational qualifications, found that personal dieticians, psychologists, plastic surgeons and even global matchmakers will also be in high demand due to increased wealth, reduced time and greater longevity. In fact, a new job of longevity consultant is predicted to emerge to advise retired people on health and financial planning.
Other boom areas will be in nanotechnology, concerned with building tiny structures to incorporate into our bodies or the environment, or bioinformatics - using genetics in drug development.
Another profession could be that of "fun employee". City and Guilds predicts that businesses will soon employ people to make work more enjoyable and, therefore, more productive.