population growth.

[Grumbold]

Available food supply is certainly important, but it can be assessed in a number of different ways. Ancient Rome was utterly dependant on the massive Grain Fleets sailing in from Egypt each autumn to avoid starvation. More than one Emperor came to power by controlling the arrival of the fleet.

You can model this using food caravans if you like or just factor that they devote some of the trade income from Rome into acquiring food from elsewhere.

It is a different point, but until the evolution of modern transportation methods each country normally has only one or two large population centres. Food and workers used to migrate into the capitol rather than expanding the size of their home towns. It could be interesting if each city above size 4 had to have at least two supporting cities of a certain smaller size to continue to grow, so your max sizes would become something like 16, 12, 12, 8, 8, 8, 8, 4, 4, 4, 4, 4, 4, 4, 4. Gradual technological improvements coould narrow the gap so things begin to even out. Even today many countries adhere to this pattern.

[S. Kroeze]

In civ3 i'd like to see population growth being totally independent of food production.

Are you kidding?!?

As pointed out by several other posters, Stuff2 seems to disregard completely the compelling importance of the availability of food and the relation between population growth/shrinkage, food, famine and diseases. Nutrition was -in the opinion of most historians- always the most important influence on population growth in the long term. I'll give some quotations:

quote: 'Throughout the agricultural period, rates of population growth were determined largely by the availability of food. Before the nineteenth century most people were chronically undernourished, and exposed at intervals to the devastating effects of famine. France, a relatively privileged country, is said to have had '10 general famines during the tenth century, 26 in the eleventh, 2 in the twelfth, 4 in the fourteenth, 7 in the fifteenth, 13 in the sixteenth, 11 in the seventeenth and 16 in the eighteenth.' Conditions were at least as bad in other countries of Europe and much worse in Asia. The last major famines occurred in England in the 1620s, in Scotland in the 1690s, in Germany, Switzerland and Scandinavia in 1732, in France in 1795 and in Ireland, with the failure of the potato crop, in the 1840s. In his general examination of demographic changes between the fifteenth and eighteenth centuries Braudel stated: "A balance between mouths to be fed and the difficulties of feeding them, between manpower and jobs, is re-established by epidemics and famines (the second preceding or accompanying the first)." The point is well illustrated by experience of the Black Death, which was preceded by serious food shortages that spread throughout Europe between 1308 and 1318. "Famine was never an isolated event. Sooner or later it opened the door to epidemics." There were four main influences which led to the predominance of infectious diseases as causes of sickness and death: the existence, probably for the first time, of populations large enough to enable some human infections to become established and others to be amplified; defective hygiene and crowding, which further increased exposure to communicable diseases; insufficient food which lowered resistance to infection; close contact with domesticated and other animals which were the probable source of many micro-organisms The great change in community size is believed to have begun about 6,000 years ago; before that time human settlements consisted of villages with less than 300 persons, much too small to maintain the human infections. It was only after the introduction of improved farming techniques, particularly irrigated agriculture, that a few cities had 100,000 persons, and only in the last few centuries after industrialization that they had half a million. Remarkably, we owe the origin of most serious infectious diseases to the conditions which led to our cultural heritage, the city states made possible by the planting of crops in the flood plains of Mesopotamia, Egypt and the Indus Valley. Except in the case of vaccination against smallpox, it is unlikely that personal medical care had a significant effect on mortality from infectious diseases before the twentieth century. Between 1900 and 1935 there was a contribution in some diseases; antitoxin in treatment of diphteria; surgery in appendicitis, peritonitis and ear infections; salvarsan in syphilis; intravenous therapy in diarrhoeal diseases; passive immunization against tetanus; and improved obstetric care in prevention of puerperal fever. But even if these measures were responsible for the whole of the decline of mortality from these conditions after 1900, which clearly they were not, they would account for only a small part of the decreased deaths which occurred before 1935. From that time the first powerful chemotherapeutic agents, sulphonamides and, later, antibiotics, came into use. However, they were certainly not the only reason for the continued fall of mortality. I conclude that immunization and treatment contributed little to the reduction of deaths from infectious diseases before 1935, and over the period since cause of death was first registered they were much less important than other influences. In the light of these conclusions concerning the twentieth century, it is most unlikely that personal medical care had a significant effect on the trend of mortality in the eighteenth and early nineteenth century. The most useful evidence of the relation between nutrition and infectious diseases comes from the experience of physicians who have worked extensively with infants and children in developing countries. As already noted this experience leaves no doubt that although malnutrition has not the same effect in every disease, in general it is a major determinant of infection rates and of the outcome of infection. In the preceding discussion, both the modern rise of population and the associated transformation of health were attributed essentially to the decline of mortality from infectious diseases. These were not the first major changes; the population of the world expanded after the transition to agriculture, and there were large increases in Western Europe between 1100 and 1350 and again between 1450 and 1650. However, these and many other less reliably recorded expansions of population and (presumably) improvements in health were all reversed in time. Only the modern changes have continued unabated: expectation of life is still increasing in developed countries, and most of their populations are rising, if at a somewhat slower rate. In the nineteenth century, however, apparently for the first time, there was effective limitation of births. It appeared first in France, where a marked decrease in the birth rate after 1789 is believed to have been due to the spread of contraceptive practices. In England and Wales the decline was delayed until the eighth decade, but its significance in relation to health can hardly be exaggerated. If the birth rate had continued at its early nineteenth century level without a compensating rise of mortality, the population today would be about 140 rather than 50 million, with devastating consequences for health and welfare. Moreover the restraint on reproduction had a direct effect on mortality, since the virtual elimination of infanticide was due mainly to avoidance of unwanted pregnancies. The limitation of numbers was therefore the essential complement without which the advances in health would in time - and on an evolutionary scale, very short time - have been reversed. In summary: The transformation of health and rapid rise of population in the Western world during the last three centuries have a common explanation: they resulted from a decline of mortality from infectious diseases. The infections declined mainly for two reasons: increased resistance to the diseases due to improved nutrition reduced exposure to infection which followed the hygienic measures introduced progressively from the late nineteenth century. The contribution of medical treatment and immunization to the decline of mortality was delayed until the twentieth century, and was small in relation to that of the other influences.'

source: T. McKeown: 'The Origins of Human Disease',1988


Another economic historian, Cipolla, wrote in a general introduction on the subject:
'Agricultural societies began very early to be interested in the numbers of their members, either for military or fiscal reasons.

However poor, the material available seems to justify some general conclusions. Compared with the data of the Roman era, medieval mortality conditions derived from Central European paleodemografic sources do not reflect substantial changes. Any agricultural society - whether sixteenth-century Italy, seventeenth-century France, or nineteenth-century India - tends to adhere to a definite set of patterns in the structure and movements of birth- and death-rates. Crude birth-rates are very high throughout, ranging between 35 and 55 per thousand and the average number of children born to a 'married' woman (using the term 'married' in its broadest connotation) by the end of her fertile period (at the age of forty-five or fifty) is at least five. Within the above indicated range, the actual value of the birth-rate in any given agricultural society varies according to numerous factors: age and sex composition of the population, sanitary and economic conditions, the prevalence of war or of peace, and, last but not least, socio-cultural factors such as the attitude toward marriage, the attitude toward birth-control etc. Death-rates are also very high, but normally lower than the birth-rates - ranging generally between 30 and 40 per thousand.

The population of an agricultural society is characterized by a normal rate of growth of 0.5 to 1.0 per cent per year. To give a meaning to this figure I can quote an exercise in astronomical arithmetic by P.C. Putnam: if the race had sprung from a couple living not long before agriculture was discovered -let us say 10,000 BC- and if its members had expanded at the rate of one per cent per year since then, the world population would form today a sphere of living flesh many thousand light years in diameter, and expanding with a radial velocity that, neglecting relativity, would be many times faster than light.(!) This has not happened because throughout the demographic history of agricultural societies death-rates show a remarkable tendency to recurrent, sudden dramatic peaks that reach levels as high as 150 or 300 or even 500 per thousand. On a few occasions these peaks coincided with wars. But much more frequently they were the result of epidemics and famines that wiped out a good part of the existing population. Reference is often made to the famous Black Death as if it were an exceptional disaster. Admittedly this unfortunate case deserves some special mention, for all Europe was then struck more or less at the same time. But one has to remember that the sudden disappearance of a fifth of the population or a third or even half, was, every once in a while, a recurrent catastrophe of local experience. The statistics collected by Father Mols for medieval and Renaissance Europe offer eloquent evidence of these disasters. The intensity and frequency of the peaks controlled the size of agricultural societies.

A highly fluctuating death-rate is an index of inadequate control over environment. The demographic density of agricultural societies tended to grow out of proportion to their technical capacity to control crop fluctuations and epidemic disease. Whenever a given agricultural population grew beyond a given 'ceiling' the probability increased of sudden catastrophes that would drastically reduce the population itself.

In normal times, a large proportion of the deaths were represented by infant mortality. Of 1000 newborn children, 200 to 400 died within a year. Many of the remaining ones died before reaching the age of seven. A famous sixteenth-century physician, Jerome Cardano of Pavia, used to maintain that he could cure anyone on condition that the patient was not younger than seven or older than seventy.

The high toll of infants and youths drastically reduced the average length of life. All available information for numerous societies seems to indicate that the 'agricultural' life expectancy at birth generally averages twenty to thirty-five years and of those who reach the age of five few have good chances of surviving beyond fifty.

The prevailing high birth-rates have distinctive effects on the age composition of agricultural populations: the number of young people is very high. In general, between one third and one half of the population is below 15 years of age; in other words, the population pyramid of an agricultural society is very broad at its base. From an economist's point of view, this means that the young non-productive population represents a heavy burden for the active adult population and this is one of the reasons why agricultural societies put children to work at an early age.'
(source: C.M.Cipolla:'The Economic History of World Population',1962)

So I strongly recommend the use of the concept of Carrying Capacity, the maximum population a particular region under the present technological level can support - well-known among historians and demographers- to determine population growth.

You can find more detailed information and some population figures in remark about the size of ancient cities and population growth.
I hope my remarks and citations may contribute to a more realistic model.

The possibility to import food -as suggested by several others- certainly makes sense, but should not be exaggerated. Only transport by sea was inexpensive enough to be used frequently over longer distances. Trade over land was generally restricted to small quantities of luxury goods. Migration should also become a possibility; yet people will only migrate when living conditions in their new environment are better.

I also would like to propose the introduction of some chance elements: the production of food shouldn't be a constant quantity. Some random element and good, average and poor harvests should be introduced. I am very curious to see a climatic model in CivIII!

S.Kroeze

CHANCE EXISTS
[This message has been edited by S. Kroeze (edited December 10, 2000).]

[jdlessl]

Impressive though it may be, what all this says to me is: "Population growth should totally dependent on birth and death rates and the occasional unfortunate disaster". Which, I believe, was the point of this thread.

Currently, as long as there is food, there will be population growth. Things like medical capabilities, education levels, standards of living, and availability of contraceptives do not make a bit of difference. This does not reflect reality, as Kroeze so kindly pointed out.

Nobody is saying that populations will grow even if there is no food. What is being suggested is that calculated growth rates be the motivator, of which food supply is probably the most important factor, but by no means was it the only one. After all, we have more food than we know what to do with, yet industrialized nations have the lowest growth rates of all.

The system you've proposed models reality quite well. Cities grow fairly quickly (compared to the civ model) when everything's going well. But after a point, it's so hard to keep the needs of the city met that some tiny disaster, big or small, comes along and wipes it out. Those ancient societies really lived on the edge, what with famines and plagues wiping out significant portions of their best cities every few decades.

I don't think you could implement climactic problems when most of the trouble takes place at times when many years go by with a click.

Lastly, some stats. In the ancient era, at 20 years per turn, assume a .75% growth rate. Over a period of 5 turns, a given population should more than double (1.0075 ^ 100). So, getting your city's population up is not a problem. Keeping it there is.

Hey, has anybody read 'A Deepness in the Sky' by Vernor Vinge. I'm utterly amazed at the similarities in the rise & fall pattern between ancient cities and (fictional) future planetary civilizations. Of course, I doubt anyone actually expected Rome to fall...

--
Jared Lessl

[Stuff2]

Basically, what i meant was this:

People do not make babies beacouse there is plenty of food. It's other factors that make people make babies. The only influence food has on the population growth is to determine how many will survive. I was thinking about game variables. I was thinking that the foodsupply should only influenced the overall health of the citizens. Birthrates should be calculated with social factors like education, poverty, contraception, health. Deathrates should be calculated from social factors like disasters, famine, health, poverty. I was thinking of no more than four or five factors and a fairly simple calculation. We don't want every turn to take forever.

About trade, i think it should be included that every society automatically will strife for a small food surplus (knowing that anything can happen). Also, the government (you) can buy food to store for later needs. (this is easiest represented with granaries).

There is no need to take every tiny thing into account (beacouse there are far too many tiny things to take into account to ever get near some actual realism, and there is also very different opinions about the reality ; since we actually don't know enough to predict the exact future beacouse it's complexity). I don't want the reality in my computer, i just want a fairly realistic model.

[Deity Dude]

Population growth as related to food should change over time.
In early periods population growth was linked to food - subsistance farming. Then technologies were developed that allowed surplus farming and food storage. I guess what i am saying is perhaps foods impact should be modified as various techs are developed.

[Grumbold]

I agree. Availability of food is the key factor which makes growth possible and to a certain extent increasing abundance of food will help improve the birth:death ratio. Beyond that point there are many more important controlling factors.

Using waterways to transport goods was certainly the cheapest method until very recently. I just think we are underestimating the trend of one or two major population centres per country absorbing all the excess food, workers and resources away from all the others to support themselves, far beyond the ability of the local resources to support. If Civ3 is to try and model real country growth over the centuries this should be something that happens automatically, or is so advantageous it encourages players to set it up instead of ICS.