The Spread of People, Agriculture, and Disease

by Katherine Athanasiades


            It is obvious that as humans have traveled and exploited the world for their own purposes, their actions have had drastic effects on the environment as they deforest the land and introduce foreign flora and fauna to different ecosystems that may not be able to cope with them.  What is not as obvious is that as humans have affected the environment, so the environment has also affected humans.  While humans have settled down and chosen an agriculturalist, sedentary lifestyle over the semi-nomadic life of the hunter-gatherer, they have become susceptible to a barrage of diseases that have adapted specifically to afflict human beings.  Because we, as humans, have come to believe that we completely dominate our environment, we find it hard to accept that perhaps the environment can also affect us in ways that may be out of our control.  However, I think that the complimentary effects of humans and the environment on each other are important facts to explore and understand in order for coexistence to continue.


            Several millennia ago, there were certain groups of humans (mainly in Eurasia) who believed that an agricultural lifestyle was more desirable and would increase chances of survival more so than the hunter-gatherer way of life that had been in existence for millions of years.  With the rise of agriculture came the domestication of the ‘farm’ animals – for example, pigs and cows (dogs had been domesticated well before these other animals).  Farmers and herders began to need more land for their crops and animals, as well as for their offspring who also became farmers and herders, and so they expanded their territories.  This territorial expansion continuously pushed hunter-gatherers off the land they had traditionally used to sustain themselves.  Eventually, agriculturalists overran most of Eurasia.  Once they discovered the New World, they similarly transported the technologies and techniques they knew for farming and herding to their new homes and took over the Americas as they had taken over Eurasia.


            Agriculture and herding has had detrimental effects on our environment in numerous ways.  Land must be cleared in order to plant crops or allow grass to grow.  This not only kills native plants, but it also alters the habitat of the location and destroys the natural homes of many wild animals.  By introducing plants and animals that are not native to the area, humans alter the environment in order to suit their own needs.  However, human alterations are not always compatible with the ecosystem, which is extremely complex and has evolved into its own sustainable system.  As we continue to alter our environment, we are speedily changing the ecosystem with high levels of destruction that it may not be able to cope with fast enough.


When agriculture is not practiced in a sustainable fashion, soil can be quickly depleted and more land may have to be cleared in order to continue the practice.  Flax is a very good example of this.  Flax quickly depletes the soil so that it is extremely difficult for anything else to survive for some time after flax has been raised.  Flax has additional environmental drawbacks in its processing – when it is “retted,” or held underwater so that undesirable parts can ferment, it releases a harmful by-product that is capable of killing fish and other beasts (Schneider).  This may alter the food chain and therefore cause food deficiencies in certain areas.


Cattle can also have harmful effects on the environment, especially when they are raised in large quantities (like in the present day).  Cattle need large areas on which to graze, and so plots of land must be cleared for these animals to roam.  In addition, they release a lot of methane into the atmosphere, which acts as a greenhouse gas and therefore affects the Earth’s climate.  As people have spread and brought with them the technology and knowledge for agriculture and herding, they increased their effects on the Earth dramatically.


            The consequences of the spread of humans and agriculture, however, are not limited to humanity’s effects on the Earth.  Our environment has responded with challenges to human existence of its own.  Though it is not necessarily directly because of the environment, humans developed many nutritional deficiency diseases when they first undertook agriculture because they were not getting a wide enough variety of food (Ponting).  This is still the case in many Third World countries.  In addition to deficiency problems, infectious diseases that were previously unknown in hunter-gatherer societies began to emerge and have negative effects on human livelihood.  Infectious diseases appeared, spread, and were sustained in response to several factors arising from the way in which humans altered their environment and living styles.  The domestication of animals provided an environment in which humans were constantly in very close contact with these animals, and consequently with the germs that these animals carried.  Over the course of time, some of these germs infected humans and mutated so that they became strictly human diseases.  One of the most well-known of these transmitted diseases is smallpox, which mutated from cowpox.  Tuberculosis also originated from a related disease afflicting cattle (Ponting).  These diseases were able to remain in existence because of the new way of life that had been adopted – people, becoming sedentary, lived in close proximity to one another and lacked effective sanitation.  Thus, they were exposed to theirs and others’ waste.  Human excrement is a very effective method of disease transmission – for example, it plays a large role in the spread of cholera.


In addition to becoming sedentary, people began to trade and communicate more with each other (Ponting).  This allowed the spread of diseases to different societies and therefore the perpetuation of their existences.  The most recent and relevant example of this is the SARS epidemic, which originated in Asia.  Because of today’s extremely fast methods of communication, SARS has been able to spread all over the world within a period of months due to people traveling the globe and carrying the disease to all different countries.


            Once infectious diseases arose with agriculture, they were aided by the grouping of people into cities.  The continuation of extremely poor sanitation allowed these “crowd diseases” to spread rampantly and unchecked (Diamond).  Poor health, due to lack of quantity and range of food, lack of sanitation, and environmental factors also contributed to the spread of disease.


            Though infectious diseases evolve and kill many humans, humans in turn evolve to have better genetic and immune defenses against the diseases.  Once a disease has been subdued or eradicated, however, new diseases arise to afflict humanity.  It is an ever-continuous cycle of humans and diseases overcoming each other.  However, the reasons for the continuation of these diseases can be found in the patterns of human settlement and survival skills.  The creation of medical technologies to help combat and prevent these diseases has been beneficial; however, sometimes nasty side effects occur like the creation of ‘super-bugs’ that are immune to current medicines and medical techniques.  Better nutrition has also helped to change the nature of disease, in that it helps people to be healthier and thus less susceptible to infection.


            In conclusion, the rise of agriculture and the spread of people have had detrimental effects on the environment.  However, these same factors have also contributed to the environment responding with infectious human diseases that have the ability to kill large portions of the population.  With new technology, many of these diseases have been stemmed in their range; however, when a new disease arises that medicine cannot yet control, it is easier for the disease to become a global epidemic because of the improvements in human travel and trade.  I think that although it is theoretically possible to change the factors that allow the destruction of the Earth and the rise of diseases, it is actually impossible to achieve the sustainability and health of the human race.  However, by understanding the complimentary effects of each on the other, I think that it is possible to alter our behaviors in such ways that problems in both directions can be greatly reduced.




Works Cited


Diamond, Jared. Guns, Germs, and Steel. New York: W.W. Norton & Comp., 1999.


Ponting, Clive. A Green History of the World. New York: Penguin, 1993.


Schneider, Jane. Rumpelstiltskin’s Bargain: Folklore and the Merchant Capitalist Intensification of Linen Manufacture in Early Modern Europe. From Cloth and Human Experience, ed. Annette Weiner and Jane Schneider. Washington: Smithsonian Institution Press, 1993.


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last updated 5/21/03