In the hindsightian sense.

About 12,000 years ago people embarked on an experiment called agriculture and some say that they, and their planet, have never recovered. Farming brought a population explosion, protein and vitamin deficiency, new diseases and deforestation. . .

Take a snapshot of the old world 15,000 years ago. Except for bits of Siberia, it was full of a new and clever kind of people who had originated in Africa . . .

They were “hunter-gatherers”. On the whole the men hunted and the women gathered: a sexual division of labour is still universal among non-farming people and was probably not shared by their Homo erectus predecessors. This enabled them to eat both meat and veg, a clever trick because it combines quality with reliability.

Why change?

I'm sure they didn't decide to change. There we're almost certainly individuals aflame with various notions about better living through, errr, whatever, but there is no record of them. Perhaps small groups did change, but they didn't prosper and continue, and so we are left to speculate. Free to speculate. And so we do, with abandon.

In the late 1970s Mark Cohen, an archaeologist, first suggested that agriculture was born of desperation, rather than inspiration. Evidence from the Fertile Crescent seems to support him. Rising human population density, combined perhaps with a cooling, drying climate, left the Natufian hunter-gatherers of the region short of acorns, gazelles and wild grass seeds. Somebody started trying to preserve and enhance a field of chickpeas or wheat-grass and soon planting, weeding, reaping and threshing were born.

Quite independently, people took the same step in at least six other parts of the world over the next few thousand years: the Yangzi valley, the central valley of New Guinea, Mexico, the Andes, West Africa and the Amazon basin. And it seems that Eden came to an end. Not only had hunter-gatherers enjoyed plenty of protein, not much fat and ample vitamins in their diet, but it also seems they did not have to work very hard.

I think it was neither desperation nor inspiration. It was simply an inevitable result of doing things repeatedly. Enough people over enough time will alter their range, like any other critter. Just as squirrels and birds plant trees - never intending to do so - and so midwife forests, people inadvertently engineer improved cultivars of favored food plants and animals. The simplest example to understand is the selection of larger and better seed heads for harvest in the wild, carrying them back to camp, dropping some in the process. Over time those seeds would spread and perhaps be somewhat protected by the mere presence of humans. Eventually someone would notice and begin to do it with more attention to outcomes.

The first farmers were less healthy than the hunter-gatherers had been in their heyday. Aside from their shorter stature, they had more skeletal wear and tear from the hard work, their teeth rotted more, they were short of protein and vitamins and they caught diseases from domesticated animals: measles from cattle, flu from ducks, plague from rats and worms from using their own excrement as fertiliser.

Less healthy? Yet there were more of them, had a lower infant mortality rate, and likely lived longer. Their diet was poor and their work was hard but they had fewer "industrial accidents" and less belligerent temperaments, and so fewer injuries and deaths from conflict. Health is a slippery word whose definition reflects preferences.

They also got a bad attack of inequality for the first time. Hunter-gatherers' dependence on sharing each other's hunting and gathering luck makes them remarkably egalitarian. A successful farmer, however, can afford to buy the labour of others, and that makes him more successful still, until eventually—especially in an irrigated river valley, where he controls the water—he can become an emperor imposing his despotic whim upon subjects. Friedrich Engels was probably right to identify agriculture with a loss of political innocence. . .

From the !Kung in the Kalahari to the Inuit in the Arctic and the aborigines in Australia, two-thirds of modern hunter-gatherers are in a state of almost constant tribal warfare, and nearly 90% go to war at least once a year. War is a big word for dawn raids, skirmishes and lots of posturing, but death rates are high—usually around 25-30% of adult males die from homicide. The warfare death rate of 0.5% of the population per year that Lawrence Keeley of the University of Illinois calculates as typical of hunter-gatherer societies would equate to 2 billion people dying during the 20th century.

Egalitarian? Only for exceedingly small values of egalitarian. The smaller, weaker and less talented "equals" died first, and the rest lived in constant awareness that they might be next. When your brother has your back you care for him much like you care for yourself, and he had better do the same to avoid being traded in for a better brother. Murder within tribes as well as between tribes was always a concern.

Constant warfare was necessary to keep population density down to one person per square mile. Farmers can live at 100 times that density. Hunter-gatherers may have been so lithe and healthy because the weak were dead. The invention of agriculture and the advent of settled society merely swapped high mortality for high morbidity, allowing people some relief from chronic warfare so they could at least grind out an existence, rather than being ground out of existence altogether.

Notice a close parallel with the industrial revolution. When rural peasants swapped their hovels for the textile mills of Lancashire, did it feel like an improvement? The Dickensian view is that factories replaced a rural idyll with urban misery, poverty, pollution and illness. Factories were indeed miserable and the urban poor were overworked and underfed. But they had flocked to take the jobs in factories often to get away from the cold, muddy, starving rural hell of their birth.

Eighteenth-century rural England was a place where people starved each spring as the winter stores ran out, where in bad years and poor districts long hours of agricultural labour—if it could be got—barely paid enough to keep body and soul together, and a place where the “putting-out” system of textile manufacture at home drove workers harder for lower pay than even the factories would. (Ask Zambians today why they take ill-paid jobs in Chinese-managed mines, or Vietnamese why they sew shirts in multinational-owned factories.) The industrial revolution caused a population explosion because it enabled more babies to survive—malnourished, perhaps, but at least alive.

The events described surely happened but the language used to describe them implies intention that was surely absent. Warfare to maintain sparse population wasn't necessary or intended so much as an inevitable consequence of hunting and gathering. With armed fellows roaming the fields and forest in search of food, and their women and weans gleaning behind them, turf battles are a sure bet. A similarly good bet is that when the range is reduced - due to higher local productivity via technology - population will be less sparse. It's the same for kings as for cabbages.

In times of prey scarcity, Homo erectus, like other predators, had simply suffered local extinction; these new people could innovate their way out of trouble—they could shift their niche. In response to demographic pressure, they developed better weapons which enabled them to catch smaller, faster prey, which in turn enabled them to survive at high densities, though at the expense of extinguishing many larger and slower-breeding prey. Under this theory, the atlatl or spear-throwing stick was invented 18,000 years ago as a response to a Malthusian crisis, not just because it seemed like a good idea.

Nonsense. People didn't invent technologies in response to demographic pressure. They invented them because there were more minds to do the inventing. New technologies are an inevitable result of population increase. It's true that this, in turn, enables even more minds to flourish, but it is opportunity rather than necessity that whelps invention.

Agriculture was presumably just another response to demographic pressure. A new threat of starvation—probably during the millennium-long dry, cold “snap” known as the Younger Dryas about 13,000 years ago—prompted some hunter-gatherers in the Levant to turn much more vegetarian. Soon collecting wild grass seeds evolved into planting and reaping crops, which reduced people's intake of proteins and vitamins, but brought ample calories, survival and fertility. . .

There is a modern moral in this story. We have been creating ecological crises for ourselves and our habitats for tens of thousands of years. We have been solving them, too. Pessimists will point out that each solution only brings us face to face with the next crisis, optimists that no crisis has proved insoluble yet. Just as we rebounded from the extinction of the megafauna and became even more numerous by eating first rabbits then grass seeds, so in the early 20th century we faced starvation for lack of fertiliser when the population was a billion people, but can now look forward with confidence to feeding 10 billion on less land using synthetic nitrogen, genetically high-yield crops and tractors. When we eventually reverse the build-up in carbon dioxide, there will be another issue waiting for us.

This morality tale may be useful, but it is wrong. Humanity is affected by technological advancement. There's a sort of step function when looked at in hindsight as population periodically jumps. But it isn't useful to see those steps as being a result of pressures, especially "ecological crises". It's possible to correlate ecological changes with population, but it isn't a causal relationship. Technology would advance over time without crises. All that is needed is more minds. Better minds could help too, but that's another discussion.