This is not easy to explain on the basis of Darwinian evolution of the individual. After all if you sacrifice your life for others before you reproduce then your genes die out. If you stay at home and take advantage of others there is a good chance you'll reproduce. When you model the implications of this mathematically it looks at first sight as if selfish behaviour is bound to win out and become increasingly prevalent in any society. There is a huge gain to the individual who takes a free ride off the hard work of others and no obvious gain to the individual who works on behalf of the community whilst someone else takes advantage.
It is only when you start to model the impact on a community that the evolutionary mechanism that allows selflessness to continue to exist becomes clear. If a group of hunter gatherers has a very strong gene for individual selfishness then there is a good chance that the group as a whole will die out as they fail to work together successfully. By contrast a group that can depend on each other and knows that one member of society will always look out for another will survive. So some evolutionary theorist such as E.O. Wilson are now concluding that early humanity could not have survived without passing on a gene for collaboration. Individuals with an urge to co-operate tended to live long enough to pass that gene on.
Humanity would not have successfully survived without a degree of invention and so our successful evolution also depended on not every individual always doing what everyone else in the group expected them to do. We needed collaboration but we also needed experimentation, risk taking, and invention.
Once you move beyond a society of simple hunter gatherers things are somewhat different. Large complex societies have developed a whole series of different ways of allocating resources that enabled people to live together. They included allocating them mainly on the basis of religion (Tibet), warlike behaviour (Gengis Khan), defined social status (Indian caste system) and economic success.
The prime method being used at the moment is the free market. It is one of many different possibilities - a social system not an inevitability. This way of organising society does some things very well. It ensures that people who provide goods and services that people want get rewarded for doing that and those that don't become poor. It therefore is very good indeed at ensuring that the things most people want now are what gets produced instead of what some part of society such as the church or the army has decided should be produced. That is why computer software was developed in the West and why the Soviet Union couldn't provide its citizens with a decent pair of jeans or interesting rock music. A free market system works by enabling every pound we spend to be a vote for what we want to be produced.
Successful as this system has been it also comes with huge problems. The votes aren't equal. If you are ill, or disabled, or old or you have learned skills that are now out of date then it is much less likely that you will be able to make and sell things that people want. Your income will be very low. If you can write a piece of software that the whole world wants to use and control its ownership then it will be very high. Left without control the free market system produces extremes of wealth and poverty. Steve Jobs ends up with more money than he knows what to do with and an unskilled labourer in Bhopal ends up working for a pittance in an unsafe factory and living in a horrible slum.
Put simply the capitalist system gives a huge incentive for selfish behaviour and leaves people who contribute selflessly feeling like mugs. Ask anyone who chose to work for the NHS on low pay because they want to help others and they will tell you that there is a huge incentive to quit the job and go and work for a private agency for more money. Every time someone does so the pressure on those staff working for something they believe in becomes greater. As they see their colleague return as an agency nurse on higher income for less responsibility those who remain have to make a hard decision. Carry on working to help the community or increase their income by moving themselves to work for an agency. The desire to help others is so firmly rooted in the psychology of some people that many nurses stick with the NHS. All the incentive is in the other direction.
So the free market system tends to produce extremes of affluence and poverty and it tends to undermine community spirit. It turns us all into competitors and gives a huge disincentive to be collaborators. In the world of hunter gatherers such a system would begin to collapse as the individuals looked to their own interests and the community became too weak to survive. In the nineteenth century when the UK produced the nearest thing the world has ever had to an entirely free market system it produced very rapid economic growth. It also produced life expectancy rates as low as 16 for a labourer in Bethnal Green in the 1840s.
Faced with these extremes ordinary people engaged in decades of long hard struggle to create a system that tried to keep the best of the vibrancy of the free market but get rid of the ugly horrors of its excesses. They worked to build a welfare state in which it was possible to get rich but it was also possible to live an ordinary life successfully as a member of a community. That system has now been under attack for over 30 years and the strains are starting to show.
Instead of living in a regulated and managed free market within a nation state we now live in a largely unregulated and uncontrolled world market that operates a reward system very similar to that which existed in the UK in the 1800s. If you win then you win big. If you lose then the chance of anyone looking out for are slim and getting slimmer by the day.
Left to its own devices the free market will always work to reward the few and to provide heavy disincentives for those who look after others. So we have a choice. We can either let the market do its job and slowly watch as the incentive system drives out the collaborative element from humanity and makes us all steadily more selfish. Or we can try and take control of the situation and start to use the power of government and international organisations to ensure that humanity doesn't go down this route. High levels of progressive taxation, the re-creation of a reliable welfare net and huge incentives to adopt environmentally sensitive ways of working and living would be where I would start. Others may have a different view. But the simple truth remains that where you decide to draw the line between the free market and social controls is the critical political choice you can make.
Margaret Thatcher famously didn't believe there was such a thing as society. Do we really want to let her successors make that a reality?