Disease and Death

Epidemics and plagues wiped out vast numbers of the population in a wide area. Persistent infection in certain regions have made human habitation impossible there.Overall endemic low-level diseases throughout human civilization have produced low levels of health and shortened life expectancy. Often the result of inadequate diet.

Hunting and Gathering Groups

Hunting and gathering ranged over a wide range of food. Malnutrition was rare. Food consumption was as high if not higher than the earliest agricultural groups. Deficiency diseases would have been rare. Modern hunting and gathering groups suffer from intestinal parasites, such as worms. These may have been common in prehistoric groups, especially in Africa. The spread of civilization out of Africa into temperate climates would likely have reduced this problem. Death in childbirth and infant mortality would likely have been high. Probably no worse than early agricultural societies or even early modern Europe. In France, ¼ of all children died before their 1st birthday. Life expectancy was short, though older people would not have been unknown. Among the San of Africa, about 1 in 10 are over 60.

Early Agricultural Societies

Agriculture exposed humans to a range of diseases not previously encountered. Result was a major deterioration in health. Settled societies meant that increasing numbers of people were living in close proximity to each other. This increased exposure to infectious disease.

Relation of Animal and Human Diseases

The domestication of animals exposed people to diseases which affected animals. In many cases domestic animals shared the same living quarters. Some animal diseases adapted to human hosts and flourished unchanged. Others altered their characteristics and became human diseases.

Many common human diseases are close relatives of animal diseases.

Smallpox is similar to cowpox. Measles is related to rinderpest and to canine distemper. Tuberculosis and diphtheria originated in cattle. Influenza is common to humans and hogs. The common cold came from the horse. Leprosy came from water buffalo. Humans now share 65 diseases with dogs, 50 with cattle, 46 with sheep and goats, and 42 with pigs

The Problem of Greater Concentration of Population

A large number of people living in cities of several thousand or even villages of a few hundred posed a major problem of waste disposal. Few early societies kept human excrement out of their drinking water. Most used one watercourse for both purposes. The mixture of water and human waste was a perfect habitat for intestinal Diseases such as cholera and dysentery were endemic.

Infectious Diseases Require Crowding Together

The steady rise in population and increasing density allowed new diseases to become established. Many infectious diseases (e.g., measles, mumps, and smallpox) require a minimum number of human hosts to
survive. Measles will die out on islands with a population of less than ½ million. The cities of Mesopotamia reached population levels this high. Other cities were close enough to make contact between
them frequent.

Bubonic Plague

It broke out in the Mediterranean in 542, arriving by a ship from northeast India, spread by fleas on black rats. The population was vulnerable and the death rate was high. The disease arrived in China in 610, again by boat from India, and killed about ¼ of the population.

Arrival of the Europeans

The Spanish conquistadors brought with them a wide range of European diseases.
Smallpox, 1518-1526 – many millions died.
Measles, 1530-1531
Typhus, 1546
Influenza, 1558-1559
Estimated casualties:
In central Mexico, the centre of the Aztec empire, the population fell from 25 million before the conquest to 1
million in 1600. The effect was to completely destroy the flourishing Aztec society.

Winning the Battle Against Infection

The pattern that has existed throughout human history has been broken in the last 200 years in the industrialized nations. Life expectancy has increased dramatically. Infant mortality has all but disappeared in the developed nations, except for those with inherited or incurable diseases. Reason: Fewer are killed by infectious diseases.

The Decline in Infectious Diseases

Factors in the decline of infection:
Some diseases have evolved into less virulent
forms.
Vaccines.
Antibiotics.
But these have all had a minor effect relative to the overwhelming importance of:
Better diet.
Improved environmental conditions.

Successes and Failures
Immunization programs:
Successful with smallpox.
Less successful with malaria.
Plague
Controlled, but not eliminated.
Influenza
Virulent strains still appearing.
The 1918 outbreak swept the entire world, resulting in 15-20 million deaths.
(Especially in Europe where people had been weakened by poor diet due to
World War I.)
Aids
First recognized in 1980s. May have crossed from monkeys. No vaccine
available.
nfection rates rising rapidly, especially in Africa