Fitness. The changes that occur in organism and
environment as a consequence of the interplay between
the two may be beneficial or detrimental to one or
both components of the system. The quality of fitness
expresses the beneficial results of this interplay.
As used by theoretical biologists, the word “fitness”
denotes the set of attributes enabling a particular orga-
nism to function effectively and to reproduce abun
dantly in a particular environment. Such fitness is
progressively achieved through the multifarious adap-
tive responses that the organism continuously makes
to environmental forces in the course of its life span.
The Harvard chemist and physiologist Lawrence J.
Henderson considered the problem of fitness from a
point of view which appears at first glance different
from that of the biologist, but is in reality comple-
mentary to it. Instead of concerning himself with the
attributes of organisms, Henderson placed emphasis on
the characteristics of the earth which are essential for
life. In his book The Fitness of the Environment (1913),
he pointed out that life as we know it implies the
existence of a certain set of physicochemical properties
in both the organism and the environment. He de-
fended the thesis furthermore that the physicochemical
conditions prevailing on the crust of the earth are
ideally suited—and perhaps uniquely so—for the
emergence and maintenance of life. The fitness of the
earth environment for life has developed progressively
in the course of cosmic evolution. In Henderson's own
words, “Darwinian fitness is compounded of a mutual
relationship between the organism and the environ-
ment. Of this, fitness of environment is quite as essential
a component as the fitness which arises in the process
of organic evolution.”
The use of the same word—fitness—to designate the
beneficial consequences of two sets of processes as
different as the organic evolution of living things and
the cosmic evolution of the earth may appear a seman-
tic artifact and indeed misleading. Yet, it has a justifi-
cation that transcends verbal analogy. As already
mentioned, organisms become transformed by re-
sponding to environmental stimuli, and they simulta-
neously transform the environment which harbors
them. Some of the physicochemical conditions that are
now regarded as essential for most forms of life were
in fact created by living things. For example, the
chemical composition and physical structure of the soil
are determined not only by its mineral basis and by
the effects on it of atmospheric elements, but also by
the effects of the animal, plant, and microbial life it
harbors. Even more striking is the fact that the con-
centrations of free oxygen and carbon dioxide that exist
today in the atmosphere of the earth differ profoundly
from those that prevailed before the appearance of life.
Our present atmosphere is the product of biochemical
phenomena that have been going on since the begin-
ning of life on earth. The compositions and structure
of the soil and of the atmosphere determine in turn
the kind of microbial, plant, and animal life that can
become established, prosper, and multiply in a given
area of the earth at a given time. Thus, life and envi-
ronment evolve simultaneously through a series of
feedback processes.
It is impossible at present to understand how the
organism-environment interplay began, since nothing
is known concerning the origin of life—unless one
counts as knowledge the crude, vague, and unsubstan-
tiated hypotheses that have recently been formulated
to explain how precellular, self-duplicating, organic
systems originally emerged from inanimate matter. It
is relatively easy, however, to imagine what kind of
feedback processes took place between even very
primitive cellular organisms and the physicochemical
environment that prevailed during the early biological
history of the earth's crust. Darwinian fitness now
implies a complex system of mutual relationships be-
tween organism and environment progressively
reached through the evolutionary mechanisms guided
by natural selection. But, as pointed out by L. J.
Henderson, “Fitness of the environment is quite as
essential... as the fitness which arises in the process
of organic evolution” (p. v).
As everyone knows, the earth environment is be-
coming further and further removed from the ideal of
fitness that Henderson had in mind. Most societies seem
willing to sacrifice environmental quality at the altar
of economic wealth and political power. Wherever
conditions are suitable for technological development,
the earth is losing not only its ecological balance and
pristine beauty, but also its fitness for biological and
mental health. The deterioration of the earth is so rapid
that environmentalists are now concerned less with
fitness than with the social and biological dangers of
modern life, in other words with the destructive aspects
of the environmental problem. In fact, the word “envi-
ronment” now evokes almost automatically pollution
of air, food, and water; wastage of natural resources;
exposure to excessive and abnormal stimuli; the dese-
cration of natural and humanized landscapes; in brief,
the thousand devils of the ecologic crisis. Yet, there
are other aspects of the relations of the environment
to life that are at least as interesting scientifically, and
as important practically, as are the nefarious effects
of human activities on environmental conditions.
Environmental factors exert such a powerful gov-
erning influence on the development of all human
characteristics that they literally shape the body and
the mind. The adaptive responses that man makes to
the physicochemical, behavioral, cultural, and even
historic stimuli that he experiences during the forma-
tive stages of his development constitute the mecha-
nisms through which he achieves biological and mental
fitness to his surroundings.
Most ancient people had empirically acquired the
poetical faith that health depends upon ways of life
in harmony with the natural world and the social
environment. In The Yellow Emperor's classic of inter
nal medicine—the oldest medical treatise in the
Chinese language—men are admonished to live in
accordance with the laws of the seasons, and with the
doctrine of the yin and the yang (Huang..., 1949).
Half a century ago, the Navajo Indians spoke in a
similar vein of their wish to live “in accord with the
mountain soil, the pollen of the native plants, and all
other sacred things.” And comparable expressions of
man's personal and indeed intimate relationship with
his total environment can be found in the legends and
mythologies of all archaic people.
The theme of man's dependence on his environment
pervaded the religious as well as the rational aspects
of early Greek civilizations. Hygeia, from whose name
our word “hygiene” is derived, was one of the personi-
fications of Athena, the goddess of wisdom. She sym-
bolized the belief that men would retain physical and
mental health if they lived within the golden rule, and
according to the laws of reason. In a more concrete
manner, the physicians of the Hippocratic school
taught that man's well-being is influenced by the qual-
ity of air, water, and food; by the topography of the
land and the direction of the predominating winds; and
by his general living habits. The fundamental principle
of the Hippocratic doctrine was that health can be
achieved only by conducting life in accordance with
natural laws and in such a manner that the body and
mind are in harmonious equilibrium with the total
environment.
The Greek philosophers and physicians were also the
first to realize clearly, or at least to communicate to
us explicitly, that man's relationships to his environ-
ment go much beyond the problems of health and
disease. In a prophetic passage of his treatise, “Of Airs,
Waters, and Places,” Hippocrates asserts boldly that
food, water, climate, soil, and topography affect not
only man's biological welfare, but also his physical
stature, temperament, behavioral patterns, military
prowess, and even political institutions.
Until late in the nineteenth century, most European
physicians held to the Hippocratic view that human
characteristics, in health and in disease, are profoundly
influenced by the external environment and therefore
could be manipulated and improved by sending pa-
tients to appropriate climates, altitudes, or geographic
situations. Needless to say, this belief was not limited
to medical circles. It was shared by many philosophers,
historians, and critics who believed that man was as
much a product of his environment as of his genetic
endowment. To illustrate the point of view of those
who took the side of the environmentalists in the nature
versus nurture controversy, it will suffice to quote here
a passage from the essay “Uses of Great Men” by Ralph
Waldo Emerson: “There are vices and follies incident
to whole populations and ages. Men resemble their
contemporaries even more than their progenitors.”
We resemble our progenitors because we inherit
from them our genetic endowment. But we resemble
our contemporaries even more, because, within a given
social environment, most members of a given genera-
tion are exposed to the same forces in early life. The
human genetic pool remains essentially the same from
one generation to the next, but its phenotypic expres-
sions change rapidly because the surroundings and
events that shape physiological characteristics and
behavioral patterns differ from place to place and from
one person to another.
As a moralist, Emerson was concerned with the
intellectual and emotional attributes of human beings,
but his aphorism is just as valid for anatomical and
physiological attributes, as can readily be illustrated
by examples taken from recent history and modern life.
