Byline: NIALL FERGUSON
IT WAS the best of times; it was the worst of times. It was the century when human beings got richer than previous generations could possibly have imagined. It was the century when, on average, people lived longer, too.
Breakthroughs in science and technology transformed the quality of life on earth.
The average person became better fed, healthier and taller. A much smaller proportion of the world's population was chained to the precarious drudgery of subsistence agriculture. People had roughly treble the amount of leisure time.
Moreover, thanks to the remarkable spread of the democratic form of government, people were also more free.
Yet - and this is surely one of the greatest of history's paradoxes - the 20th century was also by far the most violent era mankind has experienced since the dawn of civilisation, far more violent in relative as well as absolute terms than any other in history.
Significantly larger percentages of the world's population were killed in the two world wars that dominated the century than had been killed in any previous conflict of comparable geopolitical magnitude.
By any measure, World War II was the greatest manmade catastrophe of all time, killing something like 60 million people, nearly 3 per cent of the world's population in 1938.
Moreoever, the world wars were only two of many 20th century bouts of lethal organised violence.
Death tolls quite probably passed the million mark in at least a dozen other wars, as well as the campaigns of extermination waged against ethnic or social minorities by the Turkish regime during World War I, the Soviet regime from the 1920s until the 1950s and the National Socialist regime in Germany between 1933 and 1945, to say nothing of the tyrannies of Mao Zedong in China and Pol Pot in Cambodia.
There was not a single year between 1900 and 1999 that did not see large-scale organised violence in one part of the world or another. Estimates for the century's total body count attributable to violence range from 167 million to 188 million - perhaps as many as one in every 22 deaths.
So why were those 100 years the century of mass destruction as well as the century of mass consumption?
Why did murder rates rise almost in step with living standards?
To resolve this great paradox, it is not enough just to say that there were more people living closer together, or more destructive weapons.
NO doubt it was easier to perpetrate mass murder by dropping high explosives on crowded cities than it had once been to put dispersed rural populations to the sword. But if those were sufficient explanations, the end of the century would have been more violent than the beginning and middle.
In the 1990s the world's population for the first time exceeded six billion, more than three times what it had been when World War I broke out.
Moreover, weaponry was vastly more destructive. But there was actually a marked decline in the amount of armed conflict in the century's last decade.
In any case, some of the worst violence of the century was perpetrated in relatively thinly populated countries with the crudest of weapons: rifles, axes, knives and machetes.
When I was a schoolboy, the textbooks offered a variety of explanations for 20th century violence. Sometimes they blamed economic crises, as if depressions and recessions could explain political conflict.
Then there was the dreary old Marxist theory that the century was all about class conflict - that revolutions were one of the main causes of violence.
A third argument was that the 20th century's problems were the consequences of extreme versions of political ideologies, notably communism and fascism, as well as earlier evil 'isms', notably racism.
The trouble with all of these theories was that they could not tell me the answer to two simple questions. …