Is Farming Good for Our Health?

Kate Roach

Updated February 2004

Bird flu, SARS, CJD, heart disease and diabetes – do our farming practices spread these modern maladies? The evolution of farming displaced hunter-gatherer lifestyles, leading to higher food yields and larger human populations. Villages, towns and cities began to grow. But the change also brought with it shorter lifespans and more disease. So, is farming actually a healthy way of life?

10,000 years ago, a transformation was underway that would change the face of the globe and the life of its inhabitants forever. It's known as the New Stone Age or Neolithic Revolution. It covers the first technological breakthroughs that led to organised farming. With the breakthroughs came shifts in human lifestyle: from nomadic to settled, from hunting and gathering to cultivation. But also from health to disease. For although this first agricultural revolution meant more food and expanding human populations, it also brought a host of new diseases that humans had not known before.

10,000 years on, we in the civilised West have been shaken to the core by a shocking outburst of deadly new diseases. Legionnaire's disease appeared out of air conditioning vents. HIV arrived in humans via a little monkey called the sooty mangaby. Lyme disease came from deer ticks. In the UK, farming has been in the front line of the latest disease outbreaks. The BSE scandal all but destroyed public confidence in food safety. Then farming was hit again by the foot and mouth outbreak. And worse, we now live in fear of a global flu pandemic that has arisen out of the high-density chicken farms of east Asia.

Microbiologists who study these bugs and viruses have no shortage of data. Genetic technology has given them the opportunity to look directly into their genes. We now have a host of leads for new vaccinations and medicines. But for all our sophisticated knowledge, the bugs that cause disease, called pathogens, simply live on.

To reap the benefits of research in microbiology we need to understand the bigger picture. This means looking at the issue from several perspectives. Evolutionary biologists can give us insights into the circumstances that trigger the evolution of emerging pathogens. Ecologists can provide data on the interactions between people, disease, animals and the environment. While, anthropologists can provide vital clues about the spread of disease in human history. What all this adds up to is that we must consider our farming practices if we want to fully understand the story of the diseases.

The dawn of farming

The first large human settlements appeared in the Middle East – the origin of faming. Prior to this humans lived in relatively small nomadic bands, earning a living by hunting game and gathering fruits. Plant and animal domestication requires a settled lifestyle – you have to stay in one place to tend crops and care for livestock.

Typically, farming yields more food (10-100 times more per acre) than hunter-gathering. More food leads to more people, by allowing a shortened birth interval. Hunter-gatherers would space their children roughly four years apart, but the birth interval for farming peoples can be about two years. As farming practice spread around the globe, so villages, towns and then cities appeared, and grew in size. Humans had not lived in such high densities before.

These changes happened at different times in different parts of the world. But everywhere that farming spread it carried with it the same perils. Compared to their ancestors, farmers were shorter in stature and their bones were less dense. They suffered higher child mortality and in much of the Neolithic world. Life expectancy dropped from about 40 years to 30. The advent of farming brought both triumph and tragedy.

The evidence that reveals such tales of woe comes from painstakingly minute observations of the bones and teeth of ancient farmers. In childhood, illness or malnutrition slows or even halts bone growth and recovery renews it. The process leaves behind tell tale marks on the bone that can be identified by x-ray. The number and position of these marks amounts to a health record of peoples who lived thousands of years ago. In much the same way, ancient fragments of teeth show the poor health of pioneer farmers.

Farming diseases

The evidence suggests that farmers suffered from three kinds of new diseases: occupational, nutritional and infectious.

Occupational disease

Occupational diseases arose as a result of specialised division of labour. Repetitive strain injuries, arthritis and stress fractures increased dramatically in early farming peoples. For over 100,000 years of human evolution, our ancestors had been generalist labourers. A hunter-gatherer lifestyle does not include the repetitive back-breaking work that farming does. Naturally then, the new farmers, unused to such lifestyles, began to suffer (as some of us also suffer today).

Nutritional disease

Farming yields much more food per acre than hunter-gathering. But more food doesn't necessarily mean better health. As we've been told many times, good health depends upon a balanced diet. Farming disrupted the dietary balance that hunter-gatherers had enjoyed. although we live and eat comparatively well today, we still carry the legacies of poor diet. Diabetes and heart disease are both linked to diet.

A fast-growing population of the sort that typifies farming societies can lead to a population overly dependent upon starchy foods. Carbohydrate-rich cereals, like maize, rice and wheat, lack some proteins and vitamins found in a more varied diet of nuts, pulses and meat. Mineral and vitamin deficiency amounts to malnutrition, which in turn threatens the immune system. This increases the chances of epidemics.

Infectious disease

Farming sustains 10-100 times more people per acre than hunter-gathering and it is these high-density human populations that are able to sustain the pathogens that give us infectious diseases. For example, studies show that measles is likely to die out in populations numbering fewer than half a million people. This is because those who are afflicted either die or become immune, so in a small isolated population the pathogen would perish. But in large human settlements that have contact with other human settlements the bug will constantly find new victims.

Apart from limiting the spread of infection, nomadic people are able to leave their waste behind along with the microbes and worms that live in it. Farmers on the other hand are forced to live with their own dirt. It's easy for bugs to cross from one person's waste to another persons' drinking water. Collecting faeces and urine to fertilise the land is great for the crops but not so good for the workers. Parasites and bugs can literally have a field day infecting those who till the land.

Living in one place in densely packed populations has the advantage of permitting food storage (something that hunter-gatherers could rarely do). The downside is that food storage brings in rodents. They might be harbouring fleas, ticks and mosquitoes, all of which can carry fatal bugs. One ghastly example of this is the infamous bubonic plague.

Irrigation and forest clearance presents yet another opportunity for bugs. It provides ideal breeding grounds for mosquitoes. When West Africans first cleared forest land for farming, they disrupted the breeding sites of the resident species of mosquito. Its niche was taken by another more aggressive mosquito that feeds on the blood of birds but finds human blood a sweeter alternative. It carries a potentially fatal form of malaria – malignant subtertian malaria. This is as grim as it sounds and is now responsible for 95% of all malaria deaths worldwide.

It seems that early farmers were doomed to a life of sickness and disease. It's a wonder that they survived at all when nearly every agricultural practice gives a new microbe the chance of a fresh home.

Bothersome bugs

Almost every time we eat, brush our teeth, kiss a relative or cuddle our pet we are confronted with populations of microbes that are capable of breeding in the soft lining of our orifices and gut. But, we rarely get sick, much less succumb to these infections. The millions of bugs that inhabit our guts, cover our skin and luxuriate in our soft tissues generally maintain themselves in benign coexistence with our bodies. So, why do some bugs make themselves unwelcome?

When we first domesticated social animals like cows and pigs they were already carrying epidemic diseases, just waiting to be transferred to humans. Many of these diseases are new to us – not encountered before in our evolutionary history. Farming constantly brings us into proximity with bugs for which we have not evolved an immune defence. One need only think of the fatal spread of a bird flu virus to humans in Vietnam and Thailand.

Most pathogens are capable of infecting more than one host species. Up to 60% of human pathogens, including flu, sleeping sickness, Lyme disease, food poisoning and variant CJD are able to infect other animals.

Lessons to learn

Exposure to new bugs that we haven't experienced before is ongoing.

It happens because we are disrupting established ecological webs, as did the Neolithic farmers. The ecology of natural environments defines the lifestyles of those animals and plants that inhabit them (including ourselves). We should have learnt that changing our day-to-day habits risks exposure to new diseases. If we had asked an evolutionary biologist to gauge the risks involved in feeding our cattle with the remains of other livestock, perhaps we could have avoided the tragedy of human variant CJD.

But how far can we blame ourselves for feeling invincible? The last century saw the rise and rise of medicine and the fall of disease. Until the Second World War more soldiers died from war-borne microbes than died of battle wounds. Post Second World War we learned that global war could be fought without a single epidemic.

In the decades that followed the Second World War, vaccination against small pox and polio promised to rid the world of epidemics. Antibiotics cured infections in a way that seemed miraculous and sanitation also helped us keep them at bay as well. New pesticides controlled insect-borne diseases. Population numbers rocketed, forcing us to develop new herbicides and fertilisers to increase food productivity.

A complacent view arose, miracle drugs and vaccinations made it seem as though our diseases would dwindle and die. Medical science could turn its mind to modern concerns like cancer, heart disease, genetic disorders, and ageing. Unfortunately, we took our eye off the ball when we ignored our history, evolution and ecology. It's now time to wake up and learn our lessons from the past, if it's not already too late.

Find out more

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Websites

Channel 4 History
www.channel4.com/history/microsites/
H/history/plague/index.html
Takes a look at the devastation and destruction that followed from the Black Death.

The BSE Enquiry
www.bse.org.uk
Site covering the government's BSE inquiry.

World Health Organisation
www.who.int/emc/diseases
Detailed information on infectious disease around the world.

Department of Health
www.doh.gov.uk/publich.htm
Information on public health issues in the UK

The UK Creutzfeldt-Jakob Disease Surveillance Unit
www.cjd.ed.ac.uk
Information on the University of Edinburgh CJD research programme.

Department for Environment, Food & Rural Affairs
www.defra.gov.uk/corporate/consult/
sheepbse/index.htm
Shows the UK government's contingency plan if BSE spread to sheep.

Channel 4 News
News reports on foot and mouth.

Channel 4 News
News reports on BSE.

Books

Plague's Progress: A social history of man and disease by Arno Karlen (Gollancz, 1995) £7.99
Densely packed with information on the spread of disease from the bubonic plague to HIV.

Guns, Germs and Steel by Jared Diamond (Random House, 1997) £8.99
Extravagant and broad sweep through the last 13,000 years of human history. How farming influences the origins of empires, writing and disease.

The Emergence of Agriculture by Bruce D Smith (W H Freeman & Co, 1994) £16.99
A scholarly survey of the origins of agriculture in different parts of the world.

alternative Agriculture: A history by Joan Thirsk (Oxford University Press, 1997) £14.99
The author reveals how the forces which drive our contemporary interest in alternative forms of agriculture – changing eating habits, the needs of medicine – have parallels with earlier periods of our history.

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