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Cereal killer: The introduction of agriculture was followed by malnutrition and disease.
Last week, Sir Paul McCartney urged us, amid a blaze of publicity, to curb our carnivorous lifestyles and go meat-free on Mondays, in order to reduce the damage that modern agriculture does to the planet. But for all the recent talk about the pros and cons of farming, and how the methods we use are affecting the environment, a more basic point has been missed that growing crops might be damaging not just to the environment but to the development of our own species. Could it be that rather than being a boon to mankind, the invention of agriculture was, in the words of one academic, "the worst mistake in human history"?

To understand why this extraordinary suggestion could make sense, you need to visit the Leverhulme Centre for Human Evolutionary Studies in Cambridge, a shrine to modern anthropology. Its gates resemble a Cubist take on the DNA double-helix and its clouded glass windows are etched with phrases from Darwin's Origin of Species.

According to Prof Diamond, agriculture evolved about 12,000 years ago, and since then humans have been malnourished and disease-ridden compared with their hunter-gatherer ancestors. Worse, because agriculture allows food to be stockpiled and enables some people to do things other than look for food, it led to the invention of more and better weapons, soldiers, warfare, class divisions between those who had access to food and those who did not, and inequality between the sexes. This idea has been picked up again in a recent book, An Edible History of Humanity, by Tom Standage, which argues that agriculture is a "profoundly unnatural activity".

Beneath the centre's achingly modern exterior lies its greatest treasure, a basement containing 20,000 ancient skeletons. There are rows of skulls, kept in boxes with plastic windows at the front. As you walk along, you can peer into the great dark eyesockets of a skull from Sarawak, or the eggshell-thin cranium of a child from New Guinea. Some are so old they seem to have been stained with nicotine.

"Bones are like a book, recording the history of each person," explains Dr Jay Stock, an evolutionary anthropologist, as he slides out the boxes that contain the remains of ancient human beings. It was this collection that first proved to the world that humanity shares a common African ancestor. And it is this collection that has demonstrated agriculture could be bad for us.

The idea first came to prominence through Professor Jared Diamond, based at the University of California in Los Angeles. In his 1997 book Guns, Germs and Steel, he wrote that "although we believe agriculture has enabled us to lead lives of wealth, health and great longevity, it has in fact been detrimental to the human species."

Dr Stock agrees that farming has played a powerful role in distorting human development. "The disparities we see today between those who are exploited and those who exploit are all based on those early origins of agriculture," he explains. Hunter-gatherers, for example, ate a wide variety of foods, around 60-70 kinds a year. But once humans switched to agriculture, we became dependent on a small number of crops. (Today, these are wheat, rice and corn, which provide the bulk of calories for the world's population.)

The problem is that most of these staple foods do not have the nutrients essential for a healthy life and are vulnerable to disease and drought. Moreover, having a population based in one place led to poor hygiene, just as living in proximity with domesticated animals inevitably resulted in diseases being transferred between species, as today's outbreak of swine flu reminds us.

To illustrate the malign impact of agriculture, Dr Stock and one of his students, Anne Starling, examined a unique set of skeletons. All 9,000 are from the Nile Valley in Egypt, but they span an extraordinary historical range, from Neolithic hunter-gatherers through to 1500 BC.

The researchers were looking for signs of malnutrition, which are reflected in a person's teeth. Just as tree-rings can indicate the health and age of a tree, so a defect in the layers of enamel called linear enamel hypoplasia (LEH) can indicate whether a person has been ill, or deprived of food for several months.

What Dr Stock and Ms Starling discovered was that 40 per cent of hunter-gatherers who lived 13,000 years ago had LEH. Fast-forward 1,000 years, to when the Egyptians had become farmers, and the figure rose dramatically, to 70 per cent. Originally, the hunter-gatherers were about 5ft 8in, with robust skeletons. Yet once farming began, the average height decreased by four inches. Dr Stock showed me the bones of a man who lived 7,000 years ago, which are so thin and delicate they look as if they might snap.

What caused this reduction in height? One possibility is disease. A paper that Dr Stock is publishing with his Cambridge colleague Dr Andrea Migliano, in a forthcoming issue of Current Anthropology, demonstrates the link: the pair looked at pygmy skeletons from the Andaman Islands, whose body size shrank even more dramatically when they encountered Western colonialists, who brought with them diseases like influenza and syphilis. Hostile tribes who kept their distance from the newcomers actually grew taller during this period.

But while the Leverhulme collection demonstrates the drawbacks of agriculture, both in terms of our physical condition and our social development, it also shows the ways in which the benefits eventually came to outweigh the costs. The Egyptian skeletons reveal that around 4,000 years ago, farmers suddenly started to grow bigger and become more healthy, perhaps through the more efficient use of resources. The average height returned to 5ft 8in, and only a fifth of the population showed signs of malnourishment.

These results suggest that our ancestors struggled with poor health for 8,000 years before agriculture started to work in the favour of humanity, as opposed to benefiting the elites who controlled the food supply. "It's a case of whether the glass is half full or half empty," says Dr Stock. "Without the surplus of food you get through farming, we couldn't have the runaway technological innovation we see today. For instance, I can spend a lifetime in school, years doing a PhD, and then teach my students everything I know in a few months. They can then go on to become more expert than I am, pushing the boundaries of knowledge. Without agriculture, we wouldn't be able to stack innovation upon innovation."

While many scientists now agree with Prof Diamond that agriculture did lead to an increase in malnutrition, inequality and warfare, some, like Dr Stock, are challenging such a cut-and-dried assertion. Life as a hunter-gatherer, for example, may not have been quite as idyllic as anthropologists initially portrayed. "Anthropologists in the Sixties and early Seventies described humans as 'Man the Hunter', bringing back meat for the women and children, and there was an academic backlash against this," explains Dr Stock. "Hunter-gatherers became the original flower children. There was a romanticised view of indigenous cultures who were egalitarian and in touch with nature."

In fact, for many, life was probably "nasty, brutish and short", no matter how interesting the range of fruit and vegetables on offer. Dr Migliano has shown that the average life expectancy for a pygmy in the Philippines was 19. This meant that by the age of 14, most girls had already had at least one child. Other research has shown that, in hunter-gatherer societies, 15 per cent of young men are murdered: Prof Richard Wrangham, of Harvard University, has calculated that in spite of two world wars, fewer people die violently today than before the advent of agriculture.

In any case, says Dr Stock, we are quite clearly at the point of no return. Agriculture has led to a surplus of food and this in turn allowed women to have more children (albeit initially unhealthy ones), leading to a global population of almost seven billion. "A lot of the problems we are facing today stem from the advent of agriculture," he says. "But we are ingenious enough to come up with technological solutions.

"We are facing grave environmental and social issues. How we deal with them today will determine how impressed or dismayed the archaeologists and anthropologists of the future will be when they view our remains."