Resources, Population Growth,and Level of Living

A society's wealth depends on the use it makes ofraw materials, energy, and especially ingenuity.

V. E. McKelvey

ter, I believe, but in either case it is im-portant that we make a strong effort toestablish basic principles that can be ap-plied to the solution of our problems. Mypurpose in this article is to try to im-prove understanding of the underlyingprinciples both by examining theoreticalrelations and by analysing observationson the relation of natural and human re-sources to population growth and levelof living (18).

Limitations on Growth ofPopulations of Simple Organisms

Most critical observers agree that thehuman race is currently facing the most

crucial period in its entire history. Theworld population is exploding, for it isnow more than 2.7 billion and ismicreas-ing at the rate of 45 million per year

(1). If this rate of growth were to con-

tinue it would be only a few hundredyears until there would be standing room

only, and "a little after this the hypo-thetical human population would weighmore than the planet" (2). Even if popu-lation growth miraculously ceased now,

known deposits of metals and fossil fuelsof the quality currently mined would notsustain the present standard of living formore than a few scores of years. And, as

if these problems were not enough, themajor part of the civilized world is en-

gaged in a debilitating cold war, theprincipal parties to which are equippedwith weapons powerful enough to destroythe world's major cities in a matter ofhours, and to make much of the rest ofthe world nearly uninhabitable in a mat-

ter of days or weeks. These problems are

not insurmountable, but as Brown (3, p.

265) and others have emphasized, therates at which the population is increas-ing, usable resources are being exhausted,and international relations are worseningare so rapid that we must act at once ifwe are to avoid catastrophe.

Effective action can be based only on

an understanding of the interrelations ofthe basic factors controlling populationgrowth and level of living (4), not onlyamong scientists but also among politicalleaders, business men, and the public at

large. Unfortunately, however, thereseems to be so little agreement amongthe scientists that the general public can-

The author is with the U.S. Geological Sur-vey, Menlo Park, Calif.

3 APRIL 1959

not help but be confused (see 5, pp. 241-262 and 285-287, and 6 for summariesof divergent views). Many believe, as

Malthus did in 1798 and as Sir CharlesGalton Darwin (7, 8) does today, thatthe population will grow until food re-

quirements outstrip supply; it will thenbe brought to equilibrium by famine or

disaster. Others believe that advancingtechnology will make it possible to ob-tain raw materials and energy fromsources that cannot now be exploitedeconomically (3, 9, 10), so that short-ages of natural resources will not curbpopulation growth or depress the levelof living, or at least will do so only inthe very remote future. Some feel thatsince population growth appears to fol-low a logistic curve (11) that flattens as

the population becomes literate and in-dustrialized (12, 13), world populationwill stabilize before the starvation levelis reached. According to this view, "it isby no means certain that the maximumpopulation will be determined by thefood supply. It may well be that com-

fort and convenience will determine thelimit" (13). And while some believe thatpopulation growth is likely to reduce thelevel of living (14), others believe thatit has a beneficial effect on economicprosperity (15); that "in an advancingtechnology, more people mean more

plenty" (16). Even war and preparationfor war are sometimes regarded as bene-ficial economic stimulants (17).

Because the extremes of these viewsare nearly those expressed by ThomasMalthus and William Godwin at thestart of the controversy 160 years ago, itseems safe to conclude either that littleprogress has been made since then in theunderstanding of basic principles or thatnew information is not widely under-stood. The latter explanation is the bet-

A spatially limited medium favorableto the existence of some simple organ-ism could nourish only some finite num-ber of individuals if the food supply werenot replenished. The total number of in-dividuals that could be supported in sucha medium would vary directly with theinitial size of the food supply, and in-versely with the mean life-time food con-sumption of the individual. This situa-tion, in which an unreplenished foodsupply sustains only a limited number ofindividuals, is usually observed only inthe laboratory culture of such organismsas yeast, bacteria, fruit flies, and flourbeetles (19; 12, p. 31); but natural popu-lations of certain insects are known todie because of having completely ex-hausted their food supply (20).Most animal populations, however, are

supported by a continually or periodi-cally replenished food supply. Thegrowth of a given population is limitednot only by the size of the available foodsupply but also by disease, predators, orunfavorable extremes of temperature,salinity, moisture, or other physical orchemical variables in the environment.The maximum size such a populationcould attain would tend to increase assome function of the rate at which foodgenerally becomes available and of theorganism's comparative resistance to itsphysical and biologic enemies, and to de-crease in some way with increasing meanrate of food consumption of the indi-vidual organism. It should be noted thatwhile the organism may exert some in-genuity in searching for food, it is un-able to increase the amount of foodavailable in its environment.Many observations of natural and lab-

oratory populations show that when smallnumbers of a species are introduced intoa bountiful environment, the rate ofgrowth is slow at first but then increasesrapidly (12). The maximum is reachedin a surprisingly small number of gen-

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erations. After this, the size of the popu-lation oscillates slightly with seasonalchanges in food supply and environment,but it may fluctuate greatly and perhapseven decrease to zero if the food supplyor the organisms' comparative resistancediminish sufficiently. Where food is themost, critical factor, as it is likely to be,the, ize of the population is limited bycompetition for food among the indi-vidual members; many, particularly theyoung, are undernourished and do notlive out their normal life spans.

Growth of Population and Levelof Living in a Human Society

The limitations on the growth of popu-lations of simple organisms are essen-tially those cited by Malthus as control-ling the growth of human populations.Although he recognized that man can in-crease his own food supply, he believedthat it can be increased only in "arith-metic ratio," whereas population tendsto increase in "geometric ratio." Mal-thus also recognized that man might ex-ercise "moral restraint" to limit thegrowth of his numbers. He largely dis-counted this possibility, however, andconsidered that growth of human popu-lations is likely to be kept in check byundernourishment, disease, war, and dis-asters, and that because the populationwould always grow to the very limit ofits subsistence, most of mankind wouldalways be doomed to subsist at the mini-mum level.

Since Malthus' analysis and predic-tions were published, both the popula-tion and the level of living have risen tolevels that he would not have dreamedpossible (3, p. 5). Although his reason-ing is thought to have been sound bysome of his present-day supporters-whobelieve that the development of new

lands, new resources, and new techniquesmerely postponed the fulfillment of Mal-thus' predictions-subsequent develop-ments and further analysis of the prin-ciples involved show that he vastlyoversimplified the relation man bears tohis environment and underestimatedman's ingenuity in developing and utiliz-ing its resources. For example, becauseman not only seeks but, in all but themost primitive cultures, grows his foodand makes his clothing and shelter, hisessential needs include not only food butalso tools and raw materials; and even inprimitive societies he wants many morethings than are necessary for mere sub-

sistence (21, p. 86). He can satisfy bothhis needs and his wants only by exercis-ing ingenuity, and his success in defend-ing himself against his natural enemiesis in large part a measure of his ingenu-ity. In addition, man helps satisfy hisrequirements by capturing nonfood en-ergy for his own use, and-most impor-tant-his ingenuity permits him to satisfyhis needs from new kinds of sources,many of which are more copious thanthe older ones.

Fairfield Osborn (22, p. 202) speaksof the "eternal equation" that controlsthe level of living and the growth ofhuman population in various areas or so-cieties, and he implies that this equationmay be stated as follows:

Level of living =resources of the earthnumber of people

This is a fuller concept of the relationman bears to his environment than Mal-thus had, because it recognizes that man,unlike simple organisms, makes directuse of many other things besides food,and that the consumption of goods andservices is a variable in human popula-tions analogous in importance to thenumber of people. But even this conceptdoes not adequately represent the rela-tion among the factors that controlhuman life, for it implies that the "re-sources of the earth" constitute a fixedquantity that will yield a given outputper capita.A similar but less adequate concept is

that of Vogt (23), in which populationand level of living are determined mainlyby the "carrying capacity" (C) of theland; this, he says, is equal to the ratioof the biotic potential (B) of the landto produce plants for shelter, clothing,and food and the environmental resist-ance or the limitations (E) that the en-vironment places on the productive ca-pacity of the land ("C=B: E"). Vogtrecognizes that it is possible for man toalter the environmental resistance andhence to increase the carrying capacity,but the statement itself does not takeinto account the importance of other re-sources, nor does it give any direct indi-cation that the carrying capacity of theland varies with ingenuity. The carryingcapacity of the land, for example, for afood-gathering culture is several ordersof magnitude less than it is for the mod-ern science and machine culture. BothOsborn's and Vogt's concepts imply thatthe land will support no more than someoptimum number of people, but, asBauer and Yamey (21, p. 61) point out,

"the most fundamental weakness of theconcept of optimum population . . . isthe underlying idea that, with given nat-ural resources, output per head is a func-tion of numbers alone. In fact, however,real income is vitally affected by thequality of the population, and the theo-retical optimum would depend upon theskill, resourcefulness, and thriftiness ofthe population." As Kuznets (21, p. 129)put it, the major capital stock of an in-dustrialized country is not its physicalequipment; it is its body of knowledgeand the capacity and training of thepopulation to use its equipment effec-tively.

Although the factors that control hu-man life are highly complex and in largepart intangible, the fundamental ones,therefore, must include constructivetechnologic, socioeconomic, and politicalingenuity-the collective ability of agroup to obtain, distribute, and use rawmaterials and energy efficiently and todefend itself from its enemies, includingdisease and natural disaster. And insteadof thinking of "resources of the earth" asa fundamental factor controlling thelevel of living and population at a giventime, it is better to think of the net con-structive rate of consumption and use ofall types of raw materials, such as min-erals, food, and water; and of the netconstructive rate of consumption of allforms of energy, including a relativelysmall but essential amount of humanenergy as well as energy derived fromother animate and inanimate sources.We can then say that the average level ofliving of an individual in a given societywould tend to increase as some functionof the net constructive rate of consump-tion or use of raw materials, energy, andingenuity, and to decrease in some waywith increase in the number of consum-ers.

This means that if the total consump-tion and use of raw materials, energy,and human ingenuity is at some fixedvalue (as it is in a given society at agiven time), the level of living of theaverage individual decreases as the popu-lation increases; it also means that bothpopulation and level of living can berelatively high if consumption and useof raw materials, energy, or constructiveingenuity is also high. The expressiondoes not tell us, however, what the po-tential maximum limit to the means ofhuman subsistence is, nor does it tellwhether or not population in a given so-ciety will come to equilibrium at a lowor a high level of living.

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These questions will be consideredlater, but before going on it is desirableto mention that the dependence of levelof living and population on consump-tion of natural and human resources inthe various countries of the world todayis shown semiquantitatively by publishedstatistics (see 5, 24). For example, theper capita income in various countriescorrelates closely with the per capitaconsumption of steel and of energy ob-tained from commercial sources. A faircorrelation exists also between per capitaincome and such things as literacy, per-centage of students in secondary schoolsand colleges, per capita consumption ofnewsprint, and numbers of books pub-lished per capita. The correlation amongthese things is not exact because they areonly partial measures of the controllingfactors. Per capita income, for example,is a measure of level of living, but be-cause it takes no account of materialsalready purchased and in use, it is onlya partial measure of it. Steel is a key rawmaterial, but it is only one of hundredsthat are essential to industry, and againthe annual production is merely sugges-tive of the amount in use. The consump-tion of energy is hard to evaluate, forpublished statistics exclude solar energyand energy from other noncommercialsources. And of course no statistic pro-vides more than a feeble clue to theamount of ingenuity accumulated and inuse.

Yet, in spite of the difficulty of meas-uring the controlling factors, the evi-dence is ample to show that level of liv-ing is generally a function of the percapita consumption and use of naturaland human resources. Perhaps some op-timum combination of raw materials,energy, and ingenuity is required toraise the level of living of the individualto the maximum, but it seems obviousthat a large quantity of one will offseta shortage of the others, to some extentat least. Thus, it is due to "the skill andefficiency of the Swiss people that theyhave secured one of the highest standardsof living in the world" despite their pov-erty in natural resources (25, p. 154).

Limitations on Growth of Populationand Rise of Level of Living in Time

Is it possible to predict the potentialpopulation and level of living of a givenarea or of the world as a whole? Thisproblem is far more complex than theone just considered. As a beginning, we

could say that the potential level of liv-ing is an increasing function of the po-tential resources of raw materials, energy,and human ingenuity and a decreasingfunction of the potential population.This is not an adequate expression. how-ever, for it does not take adequate ac-count of additional complexities, suchas the fact that some things, like war andpopulation growth, that tend to decreaseprosperity in the long run may tend toincrease it for short periods because theycreate an expanding market and full em-ployment. These stimulants are only oftemporary value, however, and if theycome at a time when they cannot be ade-quately supported by available resourcesthey reduce the level of living and mayeven lead to disaster (26). With respectto ultimate world population growth, an-other factor not previously considered isman's requirement of a minimumamount of space in which to live. Theamount of space required is not known,but whether it is an acre or a squareyard need not concern us here; the pointis that there is a minimum space require-ment and that this would ultimatelylimit the earth's population if other fac-tors did not.The most important complication,

however, is that man himself has dem-onstrated the ability to control every oneof the variables (27, p. 18). He has notoften deliberately fixed his standard ofliving at a low level, although he hasdone even this in certain religious socie-ties, but in both primitive and advancedsocieties he has shown at times the will-ingness and ability to control populationgrowth by one or another means of fam-ily limitation. And human history re-cords an endless succession of discoveriesthat enabled man to utilize resourcesthat were not utilizable before.The discovery of fire, for example,

made it possible for man to eat foodsnot edible before and to live in placesnot previously habitable. The discoveryof agricultural methods made it possiblefor him to obtain many times as muchfood from a given area as the areayielded to the food gatherer, and the dis-covery of irrigation methods and of theuse of fertilizers during earlier civiliza-tions increased the yield many timesmore (28, p. 12; 3, pp. 13-45). And theapplication of modern science and en-gineering to agriculture-the develop-ment of mechanized farm implements,fertilizers, insecticides, modern breedingpractices, and so on-has increased theproductivity of the land beyond anything

imaginable even a half century ago. Forthe first users of copper, the only min-able copper ore consisted of good-sizedmasses of native copper, but the discov-ery of smelting and similar technologicaladvances made it possible to mine im-pure ores; the cut-off grade has droppedsteadily until it is now about 0.4 percentin the large porphyry deposits. Alumi-num, magnesium, and titanium were noteven known to the ancients and werenot thought to be valuable as structuralmaterials even by the technologists ofthe early 20th century. Examples of dis-coveries that created usable resourceswhere none existed before could beadded indefinitely. Sociological, eco-nomic, and political discoveries, such asthe invention of writing, money, andbanking, the development of trade andof specialization in labor, and the devel-opment of systems of government thatencouraged individual initiative, had asimilar and perhaps even greater effectin making it possible to obtain moregoods and services from a given areathan had been possible before.

If it were possible, therefore, to writean equation showing the interrelations ofpotential population, potential level ofliving, and potential resources, the ex-pression would show these variables todepend in some way on potential humaningenuity. It is unlikely, of course, thatman will be able to control the othervariables entirely, at least in the nearfuture, but it is highly probably thateven within short periods he will makenew discoveries or acquire new knowl-edge that may alter his future com-pletely. A recent and important exampleis the new look given the energy pictureby the discovery of nuclear power. Priorto 1939, the world's energy supplies werethought to consist mainly of the fossilfuels-a few scores of years' supply inthe form of petroleum and at most a fewthousand years' supply in coal. No oneconsidered that fissionable or fusionableelements might one day be a source ofpower, and the outlook for future sup-plies of power was dark. As recently asfive years ago, well after the productionof power by fission was known to be pos-sible, Ayres and Scarlott (29), Darwin(7, p. 65), and others who did not havethe benefit of the then classified dataon results of postwar exploration foruranium, considered it likely that theenergy derivable from nuclear powerwould not be any greater than that inthe world's coal reserves, if as great. Theenergy in high-grade deposits of uranium

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in Western countries alone, however, isnow known to be several times that in

all the fossil-fuel reserves combined; the

amount in the uranium in black shales

and phosphorites (which is being ex-

tracted in a few places now as a by-

product of other operations) is at least

ten and perhaps several hundred times

larger (30), and that in granites and

similar rocks is almost incalculable (31).

And it now appears that enormous

amounts of power will be available from

thermonuclear fusion (32). Progress in

mineral technology has also been im-

pressive and may be expected to make

available progressively lower grades and

increasingly larger resources of minerals

in the future, just as it has in the past

(10).This does not mean that William

Godwin was right in his belief that nat-

ural resources, if used and distributed

properly, would be adequate to support

man's needs in spite of his reproductive

proclivities; it does not mean that at any

given time or even ultimately there will

not be a limit to the resources-ingenuity

product, or that at any given time or

ultimately the population will not press

closely on the means of its subsistence;

and it certainly does not mean that some-

thing will turn up to solve all of man's

problems whether he tries to- solve them

or not. It means, rather, that because

man is potentially capable of controlling

his numbers, his environment, his usable

resources, and his very destiny to an un-

imaginable degree, it is not possible to

predict the limit, temporary or ultimate,

to his means of subsistence or his level

of living (33).

Stimuli to Technologic Advance

and Population Control

Although it is not practical to make

long-range forecasts of growth of popu-

lation or rise or fall of the level of living,

it is of utmost importance to learn the

circumstances under which man uses his

fabulous capacity to increase the means

of his subsistence and to control his num-

bers. Doubtless modern behavioral sci-

ence can cast much light on these ques-

tions, but for the purpose here it suffices

to approach them by analyzing present

and previous patterns of population and

economic growth. The rate of popula-

tion growth differs considerably in dif-

ferent parts of the world now, and it

probably always has. For example, the

world population is at present more than

2.7 billion and it is increasing at the rate

878

of about 1.7 percent per year (1); but

the population of northern Europe is in-

creasing at the rate of only about 0.6

percent per year, while that of Canadaand Australia is increasing at the rate of

2.4 percent and that of certain under-

developed areas like Mexico is increas-

ing at rates of more than 3 percent (26).The current average rate of populationgrowth has prevailed for only about two

decades; the largest growth has takenplace since about 1650. The world popu-

lation is thought to have been about 0.2billion at the beginning of the Christianera, and by 1650 it had grown to not

much more than 0.5 billion (5, p. 33).It took about 200 years to double thatfigure and less than 100 years to doubleit again. The distribution of the relativeincrease was extremely irregular: From1650 to 1950 the population of Africadoubled; that of Asia increased 3.8 times;Europe, 5.6 times; that of Central andSouth America, 13.5 times; and that of

America, 166 times. The largest absoluteincrease in number of people, however,

took place in Asia, whose population in

1950 was about 1.3 billion.

Populations of Western Europe

Although the population growth of re-

cent centuries has been unequally distrib-

uted, it shows in the aggregate a rapidincrease. In most of the Western Euro-

pean populations, where the increase

took place first, this rapid increase has

been followed by a decrease in rate of

growth. The curve representing their

growth since about 1700 is the S-shapedlogistic curve similar to that found in the

growth of animal populations (12, pp.

11-18); the growth it reflects has been

called the population cycle, which is

broken into four stages, as follows (25,p. 9): (i) the high-fluctuation stage,

characterized by high birth and death

rates and by a very slow, irregular in-

crease in population; (ii) the early-ex-pansion stage, characterized by a highbirth rate and a falling death rate; (iii)the late-expansion stage, characterized

by a falling birth rate as well as a fall-

ing death rate; and (iv) the low-fluctua-

tion stage, characterized by a low death

rate and a low birth rate, oscillatingslightly with booms, depressions, and

wars. Transition from one to another of

these stages represents the effect of a

change in the ratio of births to deaths,and perhaps also of changes in direction

and amount of migration. But what are

the fundamental causes of these changes?

The high-fluctuation stage in the his-

tory of the Western Europeans seems to

have been one in which population was

pretty much in equilibrium with foodproduction. Population increased in timeof plenty and declined sharply whenfamine or pestilence raised the deathrate; in the meantime substantial growthwas prevented by a high death rate thatwas the direct or indirect product of un-

dernourishment among a large segmentof the population. The early-expansionstage, which began during the 17th cen-

tury, was due "in part to graduallyimproving agricultural techniques, butprobably in greater degree to bettertransportation, which in turn stimulatedcommerce and handicraft production,and, through these, commercial agricul-ture," both in Europe and in new landssettled or dominated by Europeans (13).This tended to reduce famine, under-nourishment, and susceptibility to dis-ease, and hence led to a decline in thedeath rate. Even though this early growthwas not stimulated by much increase inthe use of fossil fuel and steel, it was

made possible, nevertheless, by increasedavailability and use of raw materials,energy, and ingenuity, all of which ex-

panded the supply of food and othernecessities.The late-expansion stage of the popu-

lation growth of Western peoples is

closely tied to the industrial or scien-tific revolution. Thus, Hubbert (34) has

shown that the population growth of thelast 15G years, the largest in human his-

tory, is closely correlated with the greatlyincreased use of energy from fossil fuels;the latter is directly paralleled by in-

creased consumption of metals and manyother raw materials. Mere production fig-ures, however, do not adequately describethe intellectual explosion that permittedman not only to prolong life by the con-

quest of disease (35, p. 7) but also to dis-cover and utilize natural treasures whose

very existence was previously unknown.The vastly increased amount of goods,services, and knowledge available forman's use performed "the western mira-cle" of simultaneously increasing popu-lation and raising the level of living (22,p. 75).The low-fluctuation stage is a recent

development, reached in western Euro-pean countries only within the last cen-

tury. It is characterized not only by a

relatively stable population but also bya rise in the level of living-an enigma

from the standpoint of Malthusian doc-trine. The causes for the decline in birthrate are complex, but three things seem

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especially significant: (i) Recent studiesof birth rates among various socioeco-nomic groups show that group differ-ences are mainly due to the differen-tial prevalence of birth-control practices(36); (ii) the net reproduction rate

among families within individual coun-

tries or areas generally varies inverselywith family income and degree of edu-cational attainment (12, p. 158; 37; 5,p. 156); and (iii) over the world as a

whole, areas that have the highest birthrates are those in which the highest pro-

portion of the population is illiterate anddependent on agriculture (13; 27, p. 50).These observations indicate that in rela-tively well educated and wealthy nationsand social groups, the birth rate dropsbecause married couples want to havefewer children, presumably because theywant to attain or maintain a higher levelof living for themselves and their chil-dren, or because they do not "wish to

bear the physical and social burdenswhich a large family brings" (38). Thebirth rate remains high among low-in-come and poorly educated groups be-cause their outlets for nervous and emo-

tional tension are restricted (12, p. 203;35, p. 296), they are not educated in theart of contraception, they are not able to

afford contraceptive devices, and they are

not well informed as to the consequences

of having a large family.It is important to note that the drop

in birth rate in Western countries hastaken place in spite of strong oppositionto family limitation. In Ireland, whereboth the Catholic Church and the state

have encouraged large families, the popu-

lation decreased from about 8.2 millionin 1845 to about 4.4 million in 1950 (35,pp. 53, 92). Death and emigration re-

duced the population by about two mil-lion during the potato famine years of1847-1852, but the remainder of the re-

duction results from a low birth rate dueto few and late marriages.

Until recently it was thought that aftera particular nation once reached the low-fluctuation stage of the population cycleits population would be stable, or at leastits further growth would be slow. In theUnited States, Canada, and Australasiancountries, however, it has been foundthat under certain circumstances popula-tion stability or slow growth is merelytemporary. In the United States the birthrate declined rather steadily during thefirst third of the 20th century, reachinga low of about 19 per thousand per year

during the 1930's (39), but in 1940 itstarted to rise, and since 1951 it has beenabout 25 per thousand. The reversal in

3 APRIL 1959

the trend of the birth rate is generallythought to be related to increased pay-

rolls and employment resulting from thedefense and war efforts, but the highpostwar birth rate is puzzling (25; 40,p. 46). At first glance it does not appear

to be caused by national prosperity, forper capita income rose in the early part

of the century while the birth rate de-clined. But inasmuch as the size of thefamily in the United States is now largelya result of a decision made by the par-

ents, it seems likely that the increasedbirth rate in the United States reflects a

recognition on the part of our young

people that their potential income doesnot require them to restrict the size oftheir families closely in order to realizetheir wants and fulfill their responsibili-ties adequately. The wish to avoid thephysical and social burdens of a largefamily may still militate against largefamilies, but the leisure afforded by a

shorter work week and by labor-savingdevices, such as the dishwasher and auto-

matic washing machine, makes it pos-

sible to have a medium-sized familywithout having as burdensome or com-

plex a life as the same responsibilitieswould have entailed in the 1920's. Itseems safe to conclude that a rise in na-

tional prosperity may stimulate popula-tion growth in late as well as early stagesof industrial development.

Population Cycle in Earlier Epochs

The main aspects of this populationcycle or growth curve appear to havebeen repeated during each of the suc-

cessive cultural epochs in the history ofmankind (12, p. 19) and during each ofthe earlier civilizations. Clough (28), inhis analysis of the factors controlling therise and fall of civilizations, finds thatall civilizations were marked by, and to

a large extent caused by, an increasedoutput per capita of goods and servicesand the accumulation of an economicsurplus. This permitted both an increasein population and a rise in the level ofliving, and it also provided time for in-tellectual and esthetic achievements-thehallmarks of civilization. The increasedoutput resulted from improvements intechnology, greater exploitation of nat-ural resources, increased efficiency oflabor resulting from specialization, accu-

mulation of capital, increased businessenterprise and leadership, improved tech-

niques of distribution, and developmentof an economic and political system thatnot only encouraged individual and

group enterprise but also permitted wideenough distribution of wealth to enablethe laborer to be a heavy consumer ofgoods and services. When the populationreached a size at which existing tech-niques, resources, capital, trade, and po-litical organization were unable to pro-vide a further increase in goods andservices per capita, population growthtapered off and the level of living gradu-ally declined. If for any reason the polit-ical and economic framework of the civ-ilization deteriorated, population actuallydecreased and entered the high-fluctua-tion stage. Later, when political or tech-nologic conditions once again favored theaccumulation of an economic surplus, a

new cycle of growth sometimes began,either in the same area or, more com-monly, in adjacent areas.

In contrast to the causes of decline inthe rate of growth of western Europeanpopulations family limitation stimu-lated by desire for a higher level of liv-ing and a less complex life-the declinein growth of population of most earliersocieties was due mainly to the positivechecks cited by Malthus. A great varietyof methods of family limitation, rangingfrom abortion and infanticide to varioussexual taboos and marriage bans, were

practiced in early societies; when prac-ticed extensively they helped make itpossible to avoid widespread starvation,but they do not seem to have been effec-tive in maintaining a high standard ofliving.Why did earlier civilizations rise and

decline? What stimulated and then de-pressed technologic, economic, social,and esthetic progress? Toynbee (41, p.570) explains that civilization arises "notas a result of superior biological endow-ment or geographical environment but as

a response to a challenge in a situationof special difficulty which rouses him[man] to make a hitherto unprecedentedeffort." He lists a number of adversitiesthat provide the necessary initial chal-lenge-hard country, new ground, defeatin war, threat of war, and penalizationimposed by reason of race, religion, or

class; further growth, he thinks, resultsfrom "an overcoming of material ob-stacles which releases the energies of thesociety to make responses to challengeswhich henceforth are internal rather thanexternal, spiritual rather than material."Though granting that necessity is oftenthe mother of invention, I believe thatthe growth of civilizations must havebeen stimulated by more than this, formany more peoples have been exposedto adversity and spiritual challenges than

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have made the grand response that thedevelopment of a civilization demands.

Clough (28, p. 9) supplies the miss-ing link in emphasizing the importanceof the ideologies of a culture, which gen-

erally become established at its very be-ginning. If in its formative stage "theculture embraces the idea that great

works of art should be created, thatknowledge of the universe should be ac-

quired, and that man should extend hiscontrol over human and physical envi-ronment, then subsequently more of theenergies of the culture will be devotedto the attainment of a high degree ofcivilization than would otherwise be thecase. . Another ideology which is im-portant for the effective development ofcivilization is a desire for a social andpolitical organization which will permitindividuals to realize their total poten-

tial as contributors to civilization." Hestresses also the importance of avoidingdestructive strife, of placing leadershipin the hands of those who would advancecivilization rather than some other cause,

of preventing such a rigid structuring ofthe culture that the individual has no

choice of action, and of increasing "therange of opportunities for alternative de-cisions.... Everything which contributesto the extension of that range, whetherit be economic surplus, the use of leisure,the development of cities, or the absenceof stultifying rigidities, is of the utmost

significance in furthering the process ofcivilization."

Whereas the rise of earlier civilizationswas marked by a gain in control over

both the physical and human environ-ments, their decline reflected a reversalof these trends. Specific causes may havebeen disappearance of economic surplus,resulting from population growth, ex-

haustion of natural resources, war, or

diversion of capital from productive in-vestments to nonproductive expenditureson costly works of art (for example, thePyramids) or luxurious living (28, p.

261); enemy conquest, the success ofwhich may be the result of the diffusionof the fallen civilization's techniques to

bordering peoples; disease or pestilence;social and political disorders, leading to

debilitating internal strife; deteriorationof leadership or government; or loss ofcreativity as a consequence of a stultify-ing religion, tradition, or social order(41, p. 581). The relative importanceof these causes is hard to assess. Popu-lation growth outstripped the production

of food and other necessities in the home-land in some and perhaps in all of theearlier civilizations, so that they becamedependent on trade and conquest to

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maintain their level of living (3, p. 24-30). Yet nearly all of these areas are nowsupporting more people at a higher levelof living; obviously, then, they did notexhaust their resources but merelyreached the production ceiling permittedby their technology and their economicand sociopolitical systems. It seems likelythat even without further technologicadvance they could have avoided or post-poned decline if they could have dealtwith subjugated peoples, competitors,and envious barbarians by means moreeffective and less expensive than mili-tary force, and if they could have pre-vented or satisfactorily dissolved internalsocial disorders. Failure to maintain orextend control over the human environ-ment, to organize their "society in sucha way that differences among individualsand groups may be at a minimum andthat what conflicts do exist may be set-tled in an equitable manner accordingto previously established rules," and toplace sufficient value on human life andfreedom (28, p. 260) seems to have beenat the root of the decline.

Populations ofUnderdeveloped Countries

If judged wholly by their rapid rateof increase, the populations of manyof the underdeveloped countries todaywould appear to be in the early expand-ing stage of the population cycle. Un-like the Western countries and earliercivilizations, however, the underdevel-oped countries began their recent growthnot because they opened new geographic,technologic, or economic frontiers butbecause Western countries introducedbetter methods of transportation, com-munication, agriculture, and-most im-portant-medicine and sanitation (35;3, pp. 57-58). Deposits of minerals andfuels have been developed in these coun-tries, to be sure, but because these havebeen largely exported to Western coun-tries they have not done much to raisethe level of living of the native popu-lace, which has remained dominantlyagricultural. The result of all this is thatdeath rates have been reduced, the popu-lations have grown, and in some coun-tries the amount of food and goods avail-able per person has diminished (42; 40,p. 48). No significant rise in level of edu-cation, which might check populationgrowth as it has in Western countries,has taken place in most of the under-developed countries, and populationgrowth seems to follow a strictly Mal-thusian pattern.

Summary of Basic Relations

This brief analysis of the relations ofpopulation growth and level of living tonatural and human resources yields sev-eral relatively simple but important prin-ciples, as follows. The means for man'ssubsistence increase with increasing con-structive consumption of raw materialsand energy and, especially, constructiveuse of ingenuity. Resources of usable rawmaterials and energy may be increasedto an unpredictable extent by the devel-opment and application of ingenuity.The most fundamental stimulus to in-genuity is a basic ideology that chal-lenges, encourages, and rewards indi-vidual initiative, freedom of thought,desire for economic gain, and thirst forknowledge. The attainment of a highstandard of living requires that the ratioof consumption to consumers be high.Such a ratio can be maintained mosteasily if the population is sufficientlyeducated to understand the benefits andthe means of family limitation and toextend its control over its physical andhuman environments by peaceful means.

References and Notes

1. R. C. Cook, Population Bull. 13, 133 (1957).2. P. B. Sears, Science 127, 9 (1958).3. H. Brown, The Challenge of Man's Future

(Viking, New York, 1954).4. Level of living is used in this article to mean

the actual per capita consumption of goodsand services. Standard of living refers to someagreed upon or accepted level of living. Seep. 387 of J. S. Davis' article [J. Polit. Econ.61, 369 (1953)].

5. W. S. Woytinsky and E. S. Woytinsky, WorldPopulation and Production (Twentieth Cen-tury Fund, New York, 1953).

6. W. Owen, Brookings Inst. Reprint No. I(1954), pp. 14-17.

7. C. G. Darwin, The Next Million Years(Doubleday, New York, 1953).

8. W. L. Thomas, Jr., et al., Man's Role inChanging the Face of the Earth (Univ. ofChicago Press, Chicago, 1956), p. 115.

9. J. Rosin and M. Eastman, The Road toAbundance (McGraw-Hill, New York, 1953);L. B. Clapp, Am. Scientist 46, 176 (1958).

10. T. B. Nolan, Science 128, 631 (1958).11. R. Pearl and L. J. Reed, Proc. Natl. Acad.

Sci. U.S. 6, 275 (1920).12. R. Pearl, The Biology of Population Growth

(Knopf, New York, 1925).13. K. Davis, Ann. Am. Acad. Political Social

Sci. 237, 1 (1945).14. J. J. Spengler, Am. Econ. Rev. 41, 343 (1951).15. J. S. Davis, J. Polit. Econ. 61, 387 (1953).16. Time 65, No. 2 (1955.)17. D. Riesman, Bull. Atomic Scientists 14, 135

(1958).18. I wish to thank P. C. Bateman, F. C. Cal-

kins, R. R. Coats, R. A. Gulbrandsen, D. F.Hewett, Arthur Lachenbruch, R. E. Wallace,and D. E. White of the U.S. Geological Sur-vey and M. King Hubbert of the Shell De-velopment Company, Curt Stern of the Uni-versity of California, Louis B. Slichter of theUniversity of California at Los Angeles, andJohn Tukey and Ralph W. Tyler of the Centerfor Advanced Study in the Behavioral Sciencesfor helpful criticisms and advice in the prepa-ration of this article.

19. T. Park and N. Woollcott, Physiol. Zool. 10,197 (1937).

20. D. Lack, in Numbers of Man and Animals(Oliver and Boyd, London, 1955).

21. P. S. Bauer and B. S. Yamey, The Economicsof Underdeveloped Countries (Univ. of Chi-cago Press, Chicago, 1957).

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22. F. Osborn, The Limits of the Earth (Little,Brown, Boston, 1953).

23. W. Vogt, Road to Survival (Sloane, NewYork, 1948), pp. 16, 22.

24. Statistical Yearbook (United Nations, N.Y.)25. PEP (Political and Economic Planning),

World Population and Resources (EssentialBooks, Fair Lawn, N.J., 1955).

26. R. C. Cook, Population Bull. 13, 41 (1957).27. K. Sax, Standing Room Only (Beacon, Bos-

ton, 1955).28. S. B. Clough, The Rise and Fall of Civiliza-

tion (Columbia Univ. Press, New York, ed.2, 1957).

29. E. Ayers and C. A. Scarlott, Energy Sources-The Wealth of the World (McGraw-Hill,New York, 1952), p. 169.

30. J. C. Johnson, U.S. Geol. Survey Profess.Paper No. 300 (1956), p. 13; M. K. Hubbert,Proc. Am. Petrol. Inst. Drilling and Produc-tion Practice (1956), p. 7.

31.

32.

33.

H. Brown and L. Silver, U.S. Geol. SurveyProfess. Paper No. 300 (1956), p. 91.H. Taylor and A. V. Tobolsky, Am. Scientist46, 191 (1958).C. G. Darwin [The Next Million Years(Doubleday, New York, 1953), pp. 16-24] re-cently set forth the view that the future canbe predicted by applying the laws of probabil-ity to the human race, and by considering therace as a whole to be analogous to a gas thatbehaves in a predictable fashion even thougheach of its molecules may behave differently.The behavior of the gas depends on both in-ternal and external conditions, and in Dar-win's analogy the internal controls are humannature and the external controls are the re-sources of the earth. This thesis might wellapply to a population of lower animals, butman's capacity to change his environment andto condition and control his nature and hisnumbers destroys the value of the analogy as

a basis for forecasting the future of the humanrace.

34. M. K. Hubbert, Smithsonian Inst. Pubis.Rept. (1950), p. 255.

35. R. C. Cook, Human Fertility (Sloane, NewYork, 1951).

36. P. K. Whelpton and C. V. Kiser, Ann. Am.Acad. Political Social Sci. 237, 122 (1945).

37. W. S. Thompson, Population Problems (Mc-Graw-Hill, New York, ed. 4, 1953), p. 194.

38. A. M. Carr-Saunders, World Population(Clarendon, Oxford, England, 1936), p. 115.

39. U.S. Bureau of the Census, Statistical Ab-stract of the United States (Washington,D.C., 1957), p. 55.

40. H. Brown, J. Bonner, J. Weir, The NextHundred Years (Viking, New York, 1957).

41. A. J. Toynbee, A Study of History, abridg-ment of vols. 1 to 6 by D. C. Somervell (Ox-ford Univ. Press, London, 1947).

42. R. C. Cook, Bull. Atomic Scientists 12, 295(1956).

Francisco Duran-Reynals was born inBarcelona, Spain, on 5 December 1899.He died in New Haven, Connecticut, on27 March 1958.

His early education, from elementaryschool through college, was in Barcelona.There too he took his M.D. degree in1925. In the course of his medical studyhe was also assistant in the laboratoryof bacteriology of the city of Barcelona.On his graduation he became a fellow ofthe "Junta para ampliacion de Estu-dios." The first year of his fellowship,1925-26, he spent at the Pasteur Insti-tute in Paris. In 1926, still under thefellowship, he came to James B. Mur-phy's laboratory in the department ofcancer research at the Rockefeller Insti-tute in New York. In 1928, when hisfellowship ended, he was appointed anassistant in that department, and in 1934,an associate.

In 1938, Duran-Reynals left theRockefeller Institute to accept an ap-pointment as research professor at YaleUniversity School of Medicine, underthe Jane Coffin Childs Memorial Fundfor Medical Research. He was also ap-pointed lecturer and research associateat Yale in 1952.He was a member of the Academia de

Medicina and of the Sociedad de Bio-logia of Barcelona and a correspondingmember of the Institut d'Estudis Cata-

3 APRIL 1959

lans and of the Sociedad de Biologia ofHavana. He was also a member of theHarvey Society, the American Associa-tion for Cancer Research, and manyother societies. He was for many years ascientific associate of the Jackson Me-morial Laboratory in Bar Harbor, Maine,and spent many summers there. In 1957he received the honorary degree of Doc-tor of Science from the HahnemannMedical College of Philadelphia. Heheld medals from the Pasteur Instituteand from universities of Liege, Brussels,and Montreal. In 1952 he received theAnna Fuller Memorial Prize for medicalresearch. He was a consultant to the U.S.Public Health Service, the National Re-search Council, and the American Can-cer Society.

During his stay at the Pasteur Insti-tute, Duran-Reynals' work had dealt pri-marily with the lysis of certain bacteria,but soon after coming to the UnitedStates he began to take an active interestin viruses. This interest deepened andwidened. At the same time the influenceof testicular extract as a "spreading fac-tor" was noted and was used fruitfully tostudy cell physiology (the ground sub-stances of the mesenchyme). The twolines of research seized his imagina-tion, and he held to both of them eagerlyand vigorously.

His studies of the ground substances

showed them to be a system of funda-mental importance influencing the rateor success of infection, metabolic changesin cells, stability of crystalloids, intimateeffects of hormones, allergy, and otherphenomena.Through investigation of a variety of

known cancer viruses, notably avian,Duran-Reynals established a number ofimportant facts concerning the natureand activity of those agents. Amongthese principles may be listed the fol-lowing: (i) These agents can exert nec-rotizing effects on cells under certainconditions, notably in the young host.(ii) They can vary, adapting themselvesto new hosts. When an "adaptation"occurs, a different type of cancer is in-duced. Thus, a single virus may be in-volved in the induction of many types ofcancer. (iii) They have definite anti-genic properties. (iv) They have theirhighest power of infection when injectedin young hosts. (v) They have a definiteepidemiological pattern.From this work Duran-Reynals con-

cluded that "cancer viruses" behavedfundamentally like other viruses and thatpossibly cancer could be considered to beof viral origin. For the sympathetic con-sideration of this hypothesis he was a

willing and tireless crusader.These conclusions led to the develop-

ment of the second phase of his programin this field of research. This consistedin trying to discover whether ordinaryviruses, especially those of the pox group,could, under certain conditions, inducecancer. Interesting and suggestive resultswere obtained, but the problem was un-solved and he was hard at work on itwhen his final illness set in.He was an extremely versatile and im-

aginative investigator. His bibliographyattests strikingly to this fact. Throughouthis activity as a brilliant research workerhe was strengthened and encouraged bythe complete partnership and active as-

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Francisco Duran-Reynals,Bacteriologist

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