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BIOLOGY IN THE SERVICE OF MAN
true measure of this research enterprise is to be found in the hopeful spirit
of the biomedical research community as it faces the future. The increas-
ing wealth of information and insight provided by molecular understanding
of normal structure and function and their pathological aberrations render
this community confident that it will be armed with ever more powerful
tools with which to undertake its noble task.
ON FEEDING MAN
In ten years' time, human beings will eat human beings in Pakistan.
PRESIDENT MOHAMMED AYUB KHAN, 1964.
If man is to control his own destiny, he must understand his world as
profoundly as he must understand himself. Only when there is a balance
between the human population and its food supply will the threat of mass
starvation be lifted. But calories alone will not suffice; the protein and
vitamin content of the food supply must also be adequate to human need.
Moreover, a balance in planetary terms could well be misleading. In the
long term, each major population group must feed itself.
Accomplishment of these goals is a major challenge to the human race,
but it is feasible. Indeed it is in prospect, although that seemed unlikely
only a few years ago. Mild optimism in this regard rests on the facts that:
1. On a worldwide basis, food supply has been increasing faster than
has population for several years.
2. Recently introduced strains of wheat, rice, maize, sorghum, and millet
have dramatically increased food production in areas in which food shortage
has been traditional.
3. Population control is gaining worldwide acceptance and its practice
is increasing, albeit less rapidly than might be hoped.
4. A sound scientific basis has been constructed for agricultural practice;
its extension, worldwide, coupled with provision of the necessary capital,
could undoubtedly assure an adequate food supply for a world population
that can limit its numbers to only moderate growth in the future
-
Modern agricultural practice is one of the greatest of scientific triumphs.
Since the turn of the century, agriculturists have been quick to utilize the
most recent applicable understanding of genetics, plant physiology, soil
chemistry, and physics. The result, combined with generous use of fer-
tilizer in the developed nations, is that an ever-diminishing fraction of the
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178 THE LIFE SCIENCES
working population is required to feed the remainder, who enjoy the most
diverse and nutritious food supply in history.
Crop Yields
GENETICS AND AGRICULTURAL PRACTICE
The primary challenge to the farmer is to achieve the greatest possible
yield of his crops. His actual choice of crop rests on market forces price
and regional eating habits-coupled with the suitability of his farm for
specific forms of tillage. Thereafter, the result depends upon the genetic
strain employed, application of fertilizer, soil and cultivation management,
control of pests and weeds, water supply, and harvest. The first, choice of
genetic strain, is undoubtedly the most successful of all applications of
genetic understanding, and in the United States is the basis of a significant
industry. For example, dozens of strains of wheat, tomatoes, and hybrid
corn are under cultivation in this country. They have been developed to
maximize crop return under diverse local circumstances mean tempera-
ture, temperature maxima and minima, amount of rainfall, soil structure,
and resistance to infection by specific viruses and fungi and also to take
advantage of heavy applications of fertilizer. Mutants tested in research
stations are selected and improved by commercial breeders, who make
stocks available to seedsmen, who in turn make them commercially avail-
able. A few examples will suffice.
Photosynthesis is the function of the leafy structure of the plant, and
crop yields can be significantly increased by maximizing that fraction of
solar energy per acre that is absorbed by the crop leaves. This is achieved
in part by the spacing of rows, but a major limitation is imposed by the
shading of lower by upper leaves. This problem can be minimized by in-
creasing the verticality of the upper leaves. Strains of all major grains are
now being bred to achieve this; already it is clear that substantial gains
will thus be realized, particularly in semitropical regions where intense
sunlight exceeds the light-absorptive capacity of the upper-leaf canopy.
Selective breeding has also improved the desirable intrinsic properties
of many major crops. Tomatoes now under commercial cultivation contain
several times the vitamin C concentration of older strains. Sugar beets
were made competitive with cane by raising their sugar content from 6 to
18 percent, while, at the same time, new strains of cane were developed
that do not flower for several months, thereby doubling their sugar content.
Success in the breeding of maize affords examples of the use of genetics
and breeding methods in agriculture. Maize, or Indian corn, originated in
prehistoric times in the highlands of southern Mexico. It has remained to
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BIOLOGY IN THE SERVICE OF MAN 179
become the most productive of grains, sometimes referred to as the back-
bone of American agriculture. At first, it was improved, even by prehistoric
man, by field selection of outstanding plants for seed. But early in this
century, the possibility of greatly increased productivity by hybridization
of inbred lines was realized. Most corn now produced in the United States
is grown from hybrids that best fit the many demands of local conditions.
When the opportunity is taken to aid corn production in developing coun-
tries, field selection of varieties is first resorted to for expediency before
undertaking the slower development of hybrids.
Corn has the drawback of being deficient in the content of the nutrition-
ally required amino acids lysine and tryptophan. Fortunately, the corn
plant was chosen early for detailed genetic mapping and study of the func-
tioning of inherited characteristics. Among the genes studied were two
designated as opaque-2 and floury-2. The action of these genes determines
in part the degree to which synthesis of the protein zein in the grain is
replaced by glutelin of higher lysine content. Incorporation by breeding
methods of one or both of these genes in the chromosomes of desirable
varieties and hybrids is now in progress. This promises to alleviate, in part,
the protein deficiency of world diet, particularly in some Latin American
and African nations.
An improvement in protein quality similar to that realized in corn is
now in progress for rice. Rice protein is nutritionally excellent, qualita-
tively, but the amount of protein per serving is rather limited. The results
to date indicate that a gain of more than 25 percent in protein content of
the rice grain over that of varieties now in use can be attained. The situa-
tion for wheat and sorghum is also promising.
Wheat and rice, like sorghum, corn, and other grains, can be bred as
dwarf varieties. The wheat and rice dwarf varieties have short, stout stems,
allowing greater numbers of plants per acre and use of fertilizers at the
higher rates necessary for attaining high yields. Resistance to some of the
prevalent diseases can be incorporated into the dwarf varieties, and the
protein content of the grain can be changed. All these endeavors are in
progress in the strikingly successful programs of the Rockefeller and Ford
_ _ _
it_ . .. ~ . . ~ . .. . ~ ~ . .
Foundations for improvement ot agriculture In developing countnes.
The soybean, which is valuable as a crop because of its high protein and
oil content, presents considerations somewhat different from those pertain-
ing to the grains. Although its use was recorded in Chinese malaria medica
as early as 2838 ~c, it was not used as a crop in the United States until
about 1900. The United States is now the leading producer, with an annual
crop of about one billion bushels.
The soybean plant was at first poorly adapted to growth in many areas.
It was discovered that its flowering and yield depended on the length of
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THE LIFE SCIENCES
the day and consequently varied strongly with latitude. Vaneties were
therefore bred for restricted latitude regions. A variety suited for culture
in Arkansas would be killed in bloom in Iowa, where the season is too
advanced for matunug when days become short enough for blooming. This
property of the plant is a display of the endogenous biological rhythm that
is also important for reproduction of many animal species and is present
in man.
The quality of the soybean can be varied by breeding to vary the oil or
protein content. The slowly changing economic need for the one or the
other allows adequate time for development of appropriate strains. Yields
of fields, however, even now are relatively low in terms of maximum known
yields; the reasons for this are now being sought, with interest centering
on factors controlling the extent of powering and retention of fruit.
Like animals, higher plants are subject to infection by many micro-
organisms by bacteria, fungi, and viruses. In a field unmanaged by man,
an equilibrium is achieved among all these, as well as insects and predators.
But man-managed monoculture, with great acreages planted with a single
strain of one crop, are far more susceptible to such infections, which are
not tolerable in agricultural practice. Moreover, few useful therapeutic
measures are either available or desirable in view of the low value of in-
dividual plants. Accordingly, the success of monoculture rests on the breed-
ing of resistant strains.
Although, even now, 10 to 15 percent of each major crop is lost to
infectious disease, virtually the whole of American agriculture consists of
plantings of strains especially bred for resistance to specific pathogens. In
this way, the wheat crop was saved from attack by bunt (stinking smut)
and rusts. Genetically based resistance to both of these diseases exists and
is constantly being exploited. Varieties are bred that have resistance to the
dominant strains of rust in a particular region. After a few years, however,
mutant strains of the rust fungus develop that are capable of invading the
wheat varieties in use. Meanwhile, other wheat varieties selected for re-
sistance to the mutant rust are developed and introduced. There is yet little
hope of breaking this cycle of resistant plant, mutant fungus, and back
again.
Beans and cotton have been protected, albeit only in part, from fungi
and root rot. The sugar-beet industry was almost abandoned because of the
huge losses to "curly top" virus until resistant strains were developed. And
the oranges of Southern California were almost lost to the virus causing
"quick decline," which was transferred by aphids through the sour-orange
rootstocks in common use. Only the last-minute discovery of resistant
rootstocks saved this industry. Numerous other instances of the application
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BIOLOGY IN THE SERVICE OF MAN 181
of genetics to practical agriculture could be described, but these should
suffice to indicate the scientific sophistication of these endeavors.
Agricultural Practice
Once a suitable strain of crop plant is available, adapted to local climate,
and as resistant as possible to serious disease, successful agriculture then
requires an adequate water supply, intelligent management of the soil,
and minimization of ravages by pests. The soil is the farmer's principal
resource, and its conservation is imperative. Optimal filth depends upon
a suitable combination of sand, silt, and clays maintained in miniature
aggregate by the degradation products of plants formed many years before
that lead to the formation of humus. The combination should prevent
puddling or compacting, permit easy penetration by root hairs, water, and
air. Salinity and lack of drainage must be avoided. Only recently has soil
received the close attention it warrants so that crop production can be
maximized by application of rather precisely formulated fertilizers, addition
of nitrogen-fixing bacteria, pesticides, and herbicides. In combination,
these have been responsible for the increments in crop yields of recent
decades. Moreover, attention must be paid not only to the major minerals-
potassium, nitrogen, phosphorus, calcium but to trace elements as well.
The nutrition of citrus trees growing on sandy soils in particular must be
watched carefully. In many of the western states particular difficulties are
met by assuring adequate iron supply for many crops and taking care with
interaction of iron, copper, zinc, and phosphate nutrition. If legumes such
as soybeans, alfalfa, or clover are raised, the presence of suitable strains of
nitrogen-fixing bacteria-the Rhizobia is necessary. Few agricultural
triumphs exceed the rich reward gained by application of traces of cobalt
to Florida grazing ranges. This metal, then found in the grasses, is utilized
by rumen bacteria for synthesis of vitamin Be.,. For grazing cattle, rumen
bacteria are the only source of this vitamin, which is entirely essential to
them as to all animals. The entire Florida cattle industry rests on the scien-
tific detective work that elucidated the basis for the emaciation of Florida
cattle in early years and provided this almost absurdly inexpensive solution.
Soils are living microcosms; if permitted to die, their useful rejuvenation
is extremely difficult. Below the surface are bacteria, actinomycetes, fungi,
and algae in prodigious numbers. An equal living mass of animals nema-
todes, mites, springtails, earthworms, potworms, ants, insect larvae, and
even the larger burrowing animals-cohabit this domain. Successful agri-
culture requires continuation of this equilibrium. But it can be seriously
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THE LIFE SCIENCES
altered by monoculture; crop rotation was long ago recognized as a partial
answer to this problem, although devised entirely empirically. It is an
expensive way to use valuable land and today need be done only for spe-
cific reasons. For example, rotation with barley can be used to reduce the
population of saprophytic fungi in the soil, which otherwise cause "take-
all" disease of wheat, or rotation of corn with beans in areas of Michigan
can be used to reduce the fungal population responsible for bean-root rot.
But it is no longer necessary to rotate other crops with legumes in order to
enrich the soil with nitrogen. When these considerations are added to
well-understood aspects of plant physiology, which dictate the manner of
seedbed preparation, use of irrigation, density of planting, and soil salinity
and acidity, soil management becomes an increasingly scientific enterprise,
which feeds us today and assures that we will transmit this paramount
heritage, the soil on which life depends, to future generations.
Meanwhile, the standing crop must compete with weed plants and sur-
vive its predators long enough to come to harvest. For centuries, manual
and then mechanical hoeing required much of the farmer's labor. The dis-
covery of a cheap chemical analog of the natural plant hormone auxin,
2,4-dichlorophenoxy acetic acid (2,4-D), in 1941 ushered in a new era.
In low doses, this compound is highly toxic to some plants and innocuous
for others. Ideally, of course, the former is the weed and the latter the
crop. A great diversity of effective compounds allows the ideal to be
approached, particularly where a broadleaf weed infects a gramineous
crop or a grass infests a broadleaf crop, as is common. A series of congeners
have since become available to spare the farmer in this classical task, be-
cause spraying with appropriate herbicides, tailored both to the major
weeds and the crop to be spared, is even more successful than mechanical
procedures.
Similarly, recognition of the insecticidal properties of DDT in 1939,
initially used against insects directly injurious to man, indicated that intel-
ligent application of understanding of insect physiology, entomology, phar-
macology, and the arts of the organic chemist could prevent crop destruction
by insects. To date, the use of 2,4-D has increased yearly even though it
has been replaced in part, and DDT is being withdrawn because of concern
for its potentially adverse effects on man, transfer to the general environ-
ment, prolonged persistence, destruction of beneficial insects and possibly
other wildlife, and stimulation of resistance in the target insects. These are
now matters of broad general concern, and it is regrettable that public
decisions must be made on the basis of our limited knowledge. But these
compounds paved the way for modern agriculture. Without their equiva-
lent, modern intensive agriculture is not possible, and, just as the continual
breeding of new crop strains is imperative, so too is a continuing search for
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BIOLOGY IN THE SERVICE OF MAN
effective herbicides and pesticides, optimally with specific effects on offending
organisms, degradable in the soil and nontoxic to man and animals. Attain-
ment of these goals will require continuously increasing understanding of
plant and insect physiology and life cycles.
Control of undesirable species by biological means is, in many ways, the
most attractive possibility for future exploration. The notion is by no
means new; attempts at such control began late in the nineteenth century.
Indeed, some 650 species of beneficial insects have been deliberately intro-
duced into the United States from overseas, of which perhaps 100 are
established. These are now major factors in the control of aphids and a
variety of scale insects and mealybugs. More recently, microbes and viruses
have been considered for these purposes, a few of which are being used;
for example, spores of the bacterium B. thuringiensis are used to control
the cabbage looper and the alfalfa caterpillar. Some insects have been
utilized for control of weeds e.g., prickly pear in Australia and the Klamath
weed in the western United States while a combination of the cinnabar
moth and the ragwort seed fly is required to keep down the population of
the toxic range weed, the tansy ragwort.
Still more imaginative and dramatic are such special procedures as the
elimination of insect species, e.g., the screwworm, by introduction of sterile
males (sterilized chemically or by gamma irradiation), thereby eliminating
this longtime scourge of southern cattle; the use of minute quantities of
synthetic or natural attractants, combined with an insecticide, have been
used to eliminate the oriental fruit fly; and the setting of traps with flashing
ultraviolet lights, which reduced the population of tobacco hornworm in
some southern regions of the United States. The sterile-male approach is
now being attempted for control of other insects, including some fruit flies
and such devastating species to man and stock as the tsetse fly. Despite the
successes in control of crop diseases and pests, losses are still serious, as
can be seen from Table 4. In the United States, much labor could be saved
and product quality enhanced through better controls. In underdeveloped
countries, the margin of safety between an adequate diet and malnutrition
is so narrow that an unusual loss, as in a locust plague, is a disaster. At
this time, it seems likely that current biological research will have some
success even against the locust.
Each of these biological and chemical procedures has necessarily been
the result of many years of investigation. Each is put into practice only
when its consequences appear to be adequately understood. Yet each must
necessarily alter the ecology of the affected region. When the pest species
is successfully eliminated, some other species will probably take its place
and may also require control. For the foreseeable future, the prospects are
bright if the requisite research effort is maintained.
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184 THE LIFE SCIENCES
TABLE 4 Crop Loss Due to Pests and Disease
PERCENTAGE OF TOTAL CROP LOST TO
CROP
Diseases Nematodes Insects Weeds
Corn 12 3 12 10
Rice 7 4 17
Wheat 14 6 12
Potatoes 19 4 14 3
Cotton 12 2 19 ~
Source: Scientific Aspects of Pest Control, NAS Publ. 1402, National Academy of Sciences, Wash-
ington, D.C., 1966, p. 27. (Data from USDA Agricultural Handbook Number 291, Losses in Agri-
culture. )
Animal Science
Meat and milk are important components of the total food supply. They
provide protein of high quality and make otherwise uninteresting diets
attractive. The herbivores, moreover, harvest the cellulose of plants, which
man cannot digest. They can graze sparsely vegetated rangeland and can be
brought to very high efficiency through management and use of biology.
In the United States, more than two thirds of the total crop production is
fed to animals.
Cattle, hogs, and sheep in the United States, taken together, total about
180 million, and there are twice that many chickens. The domestic ani-
mals of the Western World are the highly specialized results of careful
breeding and selection. Biological understanding has been crucial to
achievement of the desired goals of these breeding programs and will con-
tinue to be so.
No enterprise applies more science to the problems of breeding, nutrition,
disease, and economics than does the poultry industry. Genetic improve-
ment of poultry has yielded superlative results and holds even greater
promise for the future. There is no reason to believe that the growth rate,
efficiency of feed utilization, meat quality, and egg-laying capacity have
reached the highest possible levels. In spite of much progress in disease
control and nutrition, the mortality of older fowl is often. as high as 50
percent during the first laying year; since these animals are genetically
capable of high egg productivity for two years, reduction of this mortality
rate would yield great economic benefit. While chickens have been bred
for high laying capacity and meat production, deliberate adaptation to
diverse environments is only beginning. On a worldwide scale, geographical
conditions of day length, temperature, humidity, and altitude warrant con
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BIOLOGY IN THE SERVICE OF MAN
sideration in breeding programs if other nations are to share the boon of
abundant inexpensive eggs and chicken meat.
In light of detailed understanding of chick nutrition and of the environ-
ment conducive to maximal growth and to egg laying, chicken growing has
passed from an aspect of farming to a large industry, in which individual
"chicken factories" grow tens of thousands of chickens simultaneously,
each in its own enclosure, automatically fed, watered, and cleaned. In the
most advanced practice, a computer program, containing the nutritional
requirements of chickens and the composition of food grains, recomputes
the most economic satisfactory mixture of cereal grains, based on daily
or even hourly changes in grain prices and directs the mixing machinery
accordingly. To be sure, this conversion to a chicken industry is not without
cost. Such factories are deliberately located close to their urban markets.
Grains are transported from their sources, but whereas the chicken farmer
once returned the manure to the soil, it is uneconomic to transport manure
back to Midwestern grain fields. The latter use chemical fertilizer while
the manure accumulates outside the chicken factories, a problem not yet
adequately managed.
When dependence on milk fat in the American diet was greater than at
present, dairy-cattle breeders selected simultaneously for milk volume and
high butterfat content. With increasing "calorie watching," avoidance of
saturated animal fats and acceptance of products based on plant oils, breed-
ing attention has turned to emphasis on protein quality and content. Many
genes control the various characteristics of cattle and, unless their herita-
bility is reasonably high, selective breeding presents difficulties that will be
overcome only with expanded knowledge of the mechanisms of genetic
regulation. Attempts have been made to transplant the highly productive
dairy animals of temperate zones to more tropical climates, where animal
productivity is low and the need for dairy products great. These have
failed; even when the cows themselves thrive, their milk production is
dramatically reduced. But there is reason to suppose that genetic under-
standing, coupled with improved awareness of the environmental factors and
the physiological response of milch cows to increased temperature and
humidity will surmount the difficulty.
Like cattle breeders, swine breeders have been forced to react to in-
creased consumer demands for unsaturated fats and avoidance of hard
animal fat. Breeding for large deposits of fat beneath the skin and within
the abdominal cavity is no longer profitable because a large portion of the
market in which lard once brought high prices has been pre-empted by
vegetable oils. Now, limited fat content, maximum muscle mass, and
larger litter size are the important considerations, but crossbreeding has
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186 THE LIFE SCIENCES
been less successful than commercial breeders had hoped. Again, one must
turn to research for a solution.
The sea is one source of food that man has certainly not exploited
wisely or fully. Today about 200 species of fish are used in the human diet.
Their protein content is high and of excellent quality, their saturated fats
meager. With few exceptions, including trout, salmon, and shrimp, fish
are not harvested or farmed efficiently. Fishing is still a form of hunting
economy. If fish farming were to be undertaken on an extensive scale
worldwide, governments would be forced to reach clear and workable
agreements governing fishing rights and territorial waters. And the scien-
tific stage has not yet been set. Knowledge of the ecology of aquatic regions
is inadequate to sustain much more extensive fish catches. Fish rearing,
currently practiced for freshwater forms, is more art than science. The
behavior patterns of fish species will have to be established, with knowledge
of breeding grounds, reproductive potential, feeding habits, natural diseases,
and predators. The females of many species produce millions of eggs. If
adequate protection could be offered to fry and fingerlings, decidedly larger
catches seem possible, based on current estimates of primary photosyn-
thetic production at the sea surface. There is great potential for raising
and stabilizing production by protecting the young of food species from
hazards during this critical period.
But before such potential can be exploited, more thorough exploration
of ecological factors must be accomplished. The consequences of intro-
ducing into the natural environment large numbers of certain kinds of
animals with a high survival rate are not well known. There is a growing
awareness that, even in the sea, the consequences of man-made changes in
abundance can be far-reaching and not always to man's benefit.
There are other inadequately exploited opportunities. Shellfish could
serve as an important source of dietary protein if full advantage were taken
of available estuaries and shallow bays. Marine-biology stations have been
studying the life cycles, physiology, and nutrition of such species for many
years. Were legal obstacles removed and were there a genuine will to
achieve these goals, a substantial industry could be established and improve-
ment in human nutrition could result. There is reason to believe that sev-
eral food species can be grown in inland impoundments. The per acre
yield of catfish protein in Arkansas ponds is more than 10 times the per
acre yield of chicken or beef protein. Current studies offer the prospect
of success of shrimp culture in saltwater impoundments in areas such as
the Louisiana bayou country. In each instance, long years of study of
these species have prepared the way for an attractive future. But the task
is by no means complete. Aquatic animals also are subject to diverse
diseases; knowledge of those diseases is almost trivial, and knowledge of
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B IOLOGY IN THE SERVICE OF MAN 187
their control is even scarcer. Increased populations of edible pelagic fish
must alter the ecology of a vast region, but with unforeseen consequences.
Transplantation of major species from the Atlantic to the Pacific e.g.,
shad and striped bass- has only occasionally been successful; each such
trial must be followed closely for its secondary consequences.
One opportunity may already have been lost the opportunity to harvest
oceanic mammals, particularly some species of whales. These have already
been overhunted. But it may yet be possible to manage the supply of the
greatest of all animals in such a way as to utilize them as a steady supply
of high-protein food.
Finally, it must be remarked that the marketing of fish offers special
problems. Fish spoil readily; thus, processing plants must operate close
to the sources and inspection procedures must be rigorous. A long-sought
development now appears close to commercial realization. Fish-protein
concentrate can be prepared from a variety of "trash" fish. An almost
tasteless and odorless powder, it can serve as an important supplement to
the diets of millions of malnourished individuals at very low cost. The
alternative, enrichment of cereal flours with lysine, tryptophan, and me-
thionine, may yet prove to be economically competitive, but both must be
socially acceptable to the affected people. Meanwhile, the scientific bases
for both endeavors have been well established.
We cannot close this subject without drawing attention to what should
prove to be one of the major events in the history of human nutrition,
already well under way the "green revolution" which consists in apply-
ing breeding and management to production of the basic grain crops in
underdeveloped nations. The bleak image of lone farmers gathering meager
crops is being supplanted in some areas by scenes of abundant harvest.
Two to three years ago, for the first time since 1903, the Philippines pro-
duced more than enough rice for its own people, utilizing a new, short
stiff-strawed rice carefully engineered to thrive in Philippine paddies.
-r r -- '
In the same year, India harvested a landmark crop of wheat, some of it
the product of a sturdy short plant, bred for adaptation to the Indian farm-
ing milieu. Much of the harvest came from the north, from the fertile
Punjab, but throughout the wheat-growing area, some fields were cultivated
in the short new wheat, which yields 10 times or more the harvest of tra-
ditional varieties. In Pakistan and Turkey, farmers encountered similar
success. In southern India, some farmers planted the new rice and were
rewarded with abundant yields, as were Filipino farmers. To be sure, both
crops were aided by a year of abundant rainfall. But the remarkable
success of the new strains was self-evident, and the Indian Ministry of
Agriculture declared that the nation had turned the corner to modern agri-
culture and predicted optimistically that within a decade India might be
Representative terms from entire chapter:
agricultural practice
