AMID an astonishing surge in food prices, which has sparked riots and unrest in many countries and is making even the relatively affluent citizens of America and Europe feel the pinch, faith in the ability of global markets to fill nearly 7 billion bellies is dwindling. Given the fear that a new era of chronic shortages may have begun, it is perhaps understandable that the name of Thomas Malthus is in the air. Yet if his views were indeed now correct, that would defy the experience of the past two centuries.

Malthus first set out his ideas in 1798 in "An Essay on the Principle of Population". This expounded a tragic twin trajectory for the growth of human populations and the increase of food supply. Whereas the natural tendency was for populations to grow without end, food supply would run up against the limit of finite land. As a result, the "positive checks" of higher mortality caused by famine, disease and war were necessary to bring the number of people back in line with the capacity to feed them.

In a second edition published in 1803, Malthus softened his original harsh message by introducing the idea of moral restraint. Such a "preventive check", operating through the birth rather than the death rate, could provide a way to counter the otherwise inexorable logic of too many mouths chasing too little food. If couples married late and had fewer children, population growth could be sufficiently arrested for agriculture to cope.

It was the misfortune of Malthus - but the good luck of generations born after him - that he wrote at an historical turning point. His ideas, especially his later ones, were arguably an accurate description of pre-industrial societies, which teetered on a precarious balance between empty and full stomachs. But the industrial revolution, which had already begun in Britain, was transforming the long-term outlook for economic growth. Economies were starting to expand faster than their populations, bringing about a sustained improvement in living standards.

Far from food running out, as Malthus had feared, it became abundant as trade expanded and low-cost agricultural producers like Argentina and Australia joined the world economy. Reforms based on sound political economy played a vital role, too. In particular, the abolition of the Corn Laws in 1846 paved the way for British workers to gain from cheap food imports.

Malthus got his demographic as well as his economic predictions wrong. His assumption that populations would carry on growing in times of plenty turned out to be false. Starting in Europe, one country after another underwent a "demographic transformation" as economic development brought greater prosperity. Both birth and death rates dropped and population growth eventually started to slow.

The Malthusian heresy re-emerged in the early 1970s, the last time food prices shot up. Then, at least, there appeared to be some cause for demographic alarm. Global-population growth had picked up sharply after the second world war because it took time for high birth rates in developing countries to follow down the plunge in infant-mortality rates brought about by modern medicine. But once again the worries about overpopulation proved mistaken as the "green revolution" and further advances in agricultural efficiency boosted food supply.

If the world's population growth was a false concern four decades ago, when it peaked at 2% a year, it is even less so now that it has slowed to 1.2%. But even though crude demography is not to blame, changing lifestyles arising from rapid economic growth especially in Asia are a new worry. As the Chinese have become more affluent, they have started to consume more meat, raising the underlying demand for basic food since cattle need more grain to feed than humans. Neo-Malthusians question whether the world can provide 6.7 billion people (rising to 9.2 billion by 2050) with a Western-style diet.

Once again the gloom is overdone. There may no longer be virgin lands to be settled and cultivated, as in the 19th century, but there is no reason to believe that agricultural productivity has hit a buffer. Indeed, one of the main barriers to another "green revolution" is unwarranted popular worries about genetically modified foods, which is holding back farm output not just in Europe, but in the developing countries that could use them to boost their exports. Political folly increases in a geometrical ratio

As so often, governments are making matters worse. Food-export bans are proliferating. Although these may produce temporary relief for any one country, the more they spread the tighter global markets become. Another wrongheaded policy has been America's subsidy to domestic ethanol production in a bid to reduce dependence on imported oil. This misconceived attempt to grow more fuel rather than to curb demand is expected to gobble up a third of this year's maize (corn) crop.

Although neo-Malthusianism naturally has much to say about food scarcity, the doctrine emerges more generally as the idea of absolute limits on resources and energy, such as the notion of "peak oil". Following the earlier scares of the 1970s, oil companies defied the pessimists by finding extra fields, not least since higher prices had spurred new exploration. But even if oil wells were to run dry, economies can still adapt by finding and exploiting other energy sources.

A new form of Malthusian limit has more recently emerged through the need to constrain greenhouse-gas emissions in order to tackle global warming. But this too can be overcome by shifting to a low-carbon economy. As with agriculture, the main difficulty in making the necessary adjustment comes from poor policies, such as governments' reluctance to impose a carbon tax. There may be curbs on traditional forms of growth, but there is no limit to human ingenuity. That is why Malthus remains as wrong today as he was two centuries ago.