What Changed:
Before the agricultural revolution humans were migratory creatures that only carried the bare necessities for survival. It was not uncommon for these small packs of humans to go weeks, if not months, without any contact with others outside of the tribe. This hindered our population, but also prevented diseases from proliferating as well. It was only with the advent of the domestication of crops, such as wheat, barley, and other grains, that we began to settle down and build permanent residence. As technology for crop production increased our sedentary lifestyle became more prominent and a large increase in population is observable.
What This Means:
Our nomadic lifestyle may have limited both birth rates and lifespan, but it also prevented diseases from spreading to more than a dozen persons due to environmental barriers. Agriculture introduced animal fecal matter, dense population centers, and an increase in travel between communities.
Animals were a pivotal component in the progress of agricultural technology due to the fact that heavy loads could be added onto them, increasing food production and job specialization. Plows were a revolutionary concept that allowed for fields to yield more crops and more land to be cultivated. This relationship had its downside though; diseases such as measles (that would later go on to kill millions) is theorized to have been a bovine disease originally. It was the close proximity to fecal matter that facilitated this deadly step in evolution.
Population density increased exponentially with the permanent settlements established by farmers only increased the rapidity of disease communicability. This was largely to due with a lack of sanitation measures in houses such as: running water, ventilation, food preservation, and the ability to sanitize clothing and bed material. These factors led to not only a high rate of contagion, but also allowed for many diseases to travel with a family if they moved to avoid a plague.
Movement along rural roads has played an integral role. The domestication of horses allowed for quicker and more efficient travel, increasing the radius of available land and contacts for the average farmer. This travel was facilitated by the advent of job specialization, a consequence of the surplus of food produced by agriculture. Diseases now had a greater reach of infection as well as perfect environments awaiting them.
The New Revolution:
Many call the age of exploration a pivotal moment in human history. The blank edges of the map beguin to take shape and humans are traveling at unprecedented speeds around the globe. This progress of course carried the same problems as the ancestors of these explorers faced when they first planted the seeds of farms. With increased speed of travel for humans, infectious diseases also traveled just as quickly.
While sail boats have been replaced by aircraft and horse and buggy by automobile, the effect remains the same. Diseases today are combated by new advanced in medicine, but as Ian Morris discussed in his book “War, What is it Good For” the “Red Queen Effect” is created. This phenomenon is the relationship of offensive and defensive tactics, when one side builds a wall the other builds a siege engine to knock it down and the cycle perpetuates. This concept can be attributed to diseases today, each side advances to counter the other in an endless arms race where victory is only temporary.
The rules to this arms race are constantly changing due to the environmental factors that each side is heavily effected by. The recent changes in ocean temperatures has caused for varying weather patterns that have aided diseases in spreading. Mild winters with hot, humid summers, allow for mosquitoes carrying diseases such as Zika, Malaria, and Lyme disease to breed in different regions. The movement of these diseases into North America from deep in South American countries is signaling an alarming spread.
To combat this new advances in medicine are employed, but do little to tip the scales in favor of humans. With each new antibiotic a new, stronger, strain is discovered. This is the paradox of progress against diseases, with every advancement there is no gain in the long run. This perpetual arms race of man and germ is a relatively new, yet endless battle that will be waged for many years to come.