The word human ecology is derived from the Greek “oikos”—a dwelling place. The term refers to study of living things in their environment, their interaction with the physical world, and their relationship with other forms of life. It records the constant adjustment to change, which is in turn the basis of natural selection and the evolutionary process as described classically by Charles Darwin in 1859.
Originally, ecology was the study of plants and trees throughout the world; then it enlarged to include mammals and birds,.and their populations. The relationship between food production and population growth was noted by the political economist Malthus (1766-1834), to whom it seemed that food production followed a linear rate of expansion whereas population growth was geometric. In the animal world, there is always a dynamic equilibrium between food production and consumption. When food runs short, the population depending on it must decrease in number; the alternative is migration or starvation. Malthus predicted that the same pressures would apply tc human populations.
The concepts of demography, Darwinian evolution, and the genetic theories of Mendel (1822- 1884) developed into the science of population genetics; with the use of mathematics, further sophistication was obtained so that adaptation and evolution could be expressed quantitatively in the form of indices.
The organism and the environment are delicately balanced in an ecosystem, which is primarily driven by solar energy. Through photosynthesis, plants are the basic producers: herbivores eat the plants; carnivores eat the herbivores and the plants. The waste from these processes is handled by lower orders such as bacteria and fungi, and simple organic substances and minerals are returned to the environment for recycling. Although all these substances are conserved in the ecosystem, energy is dissipated as heat, and this is constantly replenished by the sun.
Thus, it is apparent that modern ecology is essentially, an interdisciplinary subject which probes into the manner of the practical organization of living things in our biosphere. Without this ecologic perspective, many discoveries at the molecular level could be without meaning; and in our search for the understanding of life, it is necessary to realize that both reductionist and interdisciplinary approaches are important.
Man has a special place in the ecosystem because he has learned to cultivate his food sources deliberately and improve the productivity of the land with irrigation and with fertilizers. This behavioral asset has given him dominance in the ecosystem, and has allowed him to adapt easily to ever-changing environmental circumstances. Physiologic adaptation alone would not have given him this unique position. Although man has made a dramatic impact on his own environment, this aspect has hardly been a feature of medical education. The physician and *the ecologist are both devoted to the welfare of a species, but there the contact ends.
The medical man’s traditional primary concern has been for the individual; the applied biologist is more concerned with the population. Their different philosophies may be seen in their attitudes, for example, on the assessment of a pesticide. The medical man is prepared to accept the results of acute or chronic toxicity tests, and will of course be concerned when individuals receive fatal doses by misuse or accident; the ecologist does not consider these physiologic criteria to be adequate, and is more anxious to assess the situation on a population basis and in terms of the other disciplines which make up ecology.
The ecologist has the advantage of seeing the picture as a whole, and the community will increasingly rely on him for early warning signals; his data must therefore be intelligible and precise enough to form the basis of action by the community.
Man’s Adaptability And The Study of Human Ecology You Must Know
Man has remarkable capacity to adapt to diverse environments, and as long as he continues to adapt there will be little to see at the cellular or molecular level. When changes are detected at these levels, it is as if the last bastions of adaptation have fallen; in retrospect, we would have done better to comprehend the various forces that had been assailing the cell. If, in the examination of an adverse environment, one reads that “no lethal or toxic effect has been shown,” this may merely mean that, at present, biologic and statistical techniques are too crude to detect anything except death of the cell.
Such a report would have us believe that the effect is not harmful; this use of null hypothesis — which denies that the phenomenon exists unless it can be proved—has a special appeal for those who are responsible for legislation. For example, in spite of the evidence of clinical intuition and obvious loss of amenity in early stages of a noise nuisance, legislation tends to be delayed until there is proved damage to cochlear tissue and subsequent deafness.
How does one translate from the cell to the individual and to society?
This concept is one of level of organization and was studied by Rudolf Virchow (1821-1902), who had already established the cellular basis of disease. Virchow extended these ideas to include the organization of living matter at the level of the organ and at the level of the individual. He recognized that cells in whatever groups —organs, individuals, societies or populations — depend for their survival on their environment, i.e., their organization; moreover, he saw that there was a human analogy and believed it his own civic responsibility to ensure that attention was given to human organization at various levels. After being a cellular pathologist and physician, he involved himself in epidemiology and public health, which led him logically to politics and anthropology.
The practice of medicine teaches us a great deal about the individual as a patient in hospital. We now need to know much more about his environment and background away from the hospital context, as he faces the reality of his daily life. (Edholm). There are two important reasons for knowing about man’s habitual activity. The first is to give some idea about man himself, anticipating and, if possible, avoiding the hospital situation. The second is to see what effect man’s activities have on his environment.