Is it more dangerous for us than for our ancestors?

The shortest possible answer is: look at the differences between developing and industrialised countries. Isn’t the different life expectancy quite revealing? The comparison is not quite fair, however, because also in developing countries many risks of modern society are present, in some cases they are even worse than in highly developed and controlled industrial countries. Tony McMichael has written in his book Human frontiers, environments and disease that the turning point was in fact the introduction of agriculture and pastorialism about 10,000 years ago. It guaranteed food for more people, but at the expense of an unbalanced diet as compared with the hunter-gatherer societies collecting their food from a number of different sources.

Food availability as the limiting factor

During the early Stone Age, the population of the world was 5 to 8 million people, i.e. about one thousandth of the present number. Because of the long distances between tribal groups, infectious diseases were rare, and illnesses such as measles or tuberculosis had no chance of developing. Food shortages at the most difficult periods of the year limited the increase of populations. In the north, the limiting period was winter, in many warm areas it was the dry period. In addition, hunting, especially big game hunting, was dangerous. Therefore the average life expectancy was a mere 20 to 25 years.

The conditions changed dramatically when pastorialism developed in the Middle East (goats and sheep were tamed about 10,000 years ago), and very soon also agriculture started to develop.

Wheat was created via a genetic recombination in the Middle East, and people started actively to cultivate the new productive plant. In fact, the plant needed human help, because its heavy seeds had no way of spreading naturally. Agriculture was able to provide food for many more people in the same area than could be provided by hunting and gathering natural plant seeds. Continuous agriculture lead to permanent settlements, villages and small towns started to develop, and population increased. Since it was possible to store wheat, the difficult bottlenecks of the year could be overcome, and as we see in the advice of Joseph to the Egyptian Pharaoh, it was even possible to overcome occasional droughts lasting more than one year. It became also possible to support non-productive members of the society, e.g. the elderly. So for the first time in history, the Bible stated: “The days of our years are threescore years and ten.” This 70 years was possible for very few, and the normal life expectancy was still only about 30 years.

Microbes attack

Living together with domestic animals as well as the dense population created many hygienic problems. The availability of food attracted mice, rats and flies, and they also spread microbes causing diseases. Many domesticated animals were herd animals that carried species-specific infectious diseases, and many of the animal microbes adapted themselves to infect humans. This was the beginning of many human infectious diseases. Influenza virus from birds and pigs infected also human beings. Ancestors of smallpox and tuberculosis in cattle adapted themselves into human forms of these deadly diseases. Whooping cough originated from pigs or dogs.

Even now, there are animal diseases that are also infective to humans. Such diseases are called zoonoses, and they include salmonellosis (e.g. murine typhus), listeriosis from cattle or milk, and diarrhoea caused by campylobacteria in drinking water contaminated with animal faeces. Psittacosis of birds can also easily infect humans, as can many infections of monkeys. Therefore tropical pets can be very dangerous unless they are professionally bred and pass strict health inspections. Rabies may be acquired from dog bites. Yersinia bacteria causing plague can take advantage of another kind of route; they are spread to humans from mice and rats by lice.

Man has adapted himself to these new pests over the millennia to some extent. Many of them are now known as children’s diseases (e.g. measles, rubella). After suffering a reasonably mild disease, the individual often gains life-long immunity. These diseases were, however, life-threatening in naïve populations. This was dramatically seen when Europeans brought these diseases to the Americas after the “discovery” of that continent. American Indians were totally susceptible to the diseases, and as much as 90% of the population in some areas died from “children’s diseases” such as smallpox and measles. This was one major reason why Europeans were able to conquer an entire continent with rather limited military might.

Europeans had met this same challenge much earlier. Many contagious diseases resided in India for millennia, because the population density was already high there. The old slow caravans could not bring these diseases to Europe, because individuals who became ill on the voyage either recovered or died before getting back home, and could not infect others.

During the Roman Empire, faster routes were discovered to India, the so-called Silk Road, a shorter caravan route to India and China, and shipping routes became faster. The consequence was the Antonine plague in the years 165 to 180, and other epidemics. The plague in A.D. 165 was in fact smallpox rather than bubonic plague, and some of the epidemics may have been measles. The Roman Empire never fully recovered from these catastrophes. These diseases have changed the history of mankind perhaps more than generally realised. After the times of antiquity, the next deadly wave was the Black Death of the 14th century which probably killed more than a third of the population in Europe.

Only during the nineteenth century were environmental aspects taken into consideration. Drinking water was realized to be crucial in the spread of cholera. Queen Victoria’s physician John Snow proved that by closing certain wells in London it was possible to prevent new cholera cases in their supply region. It was shown that the wells were being contaminated by the water from the River Thames, because sewage was fed into the river upstream of the wells. At that time, bacteria had not yet been proven to be responsible for diseases. Only after the discoveries of Louis Pasteur, Robert Koch and many others was it understood why hygiene was so important. It has been said that one of the greatest achievements in environmental health has been disinfection of drinking water that virtually brought to an end the spread of diseases such as cholera in Europe in the beginning of the twentieth century. It has also prevented many other infections transmitted by water.

Introducing chemicals

Rapid industrialization starting in the 18th century brought with it chemical pollutants. On the other hand, it should be remembered that the writer and philosopher Seneca complained already in A.D. 61 that urban air in Rome was so filthy from the smoke from the many chimneys that he could not breathe, and had to leave for his countryside retreat. Even in the Stone Age, open fires in the caves must have produced a lot of dangerous smoke even though promoting health by heating the immediate surroundings and scaring off potential predators.

The introduction of coal to replenish largely depleted fuel resources of firewood for heating, and for energy production for the newly started industries, soon caused massive problems for urban air. Depending on the area and conditions also other sources of problems emerged: heavy metals, carbon monoxide, and carcinogenic chemicals. Later, motorized traffic became more common – and with that came oxides of nitrogen and ozone. Water pollution also worsened due to the sewage produced by industries and cities.

Crowded conditions, especially of workers housed next to factories, caused also risks of accidents, and many chemical accidents have occurred. Some of the best known are the explosion of a liquid gas tank in Mexico City (1984), and the leak of methyl isocyanate chemical in Bhopal (1984). These accidents killed thousands of people as well as causing tens of thousands of serious injuries.

In other words, problems have gone hand in hand with development. There is probably no new innovation that has not been followed by adverse effects of some sort. However, when the average life expectancy in Western Europe has increased to 80 years, there is no reason to look back with nostalgia to the previous centuries or millennia as being “more healthy than the present time.”

The major risks to humans during history have been food shortage, microbes, and pollutants. Increasing life expectancy is the most unequivocal measure of a decrease in the total risk level.

Notes and references

One level up: Perception of the risks around us

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