The House We Live in; 21; Christian

I'm not a good friend, but I'm not a good friend. Man, man's God, the world between, in this post-atomic age. In the park of the University of Pennsylvania probes these areas with his guest today, physiologist John Christian of the Penrose Research Laboratory. Dr. Christian, on the previous occasion, Fairfield Osborn spoke about the changes to the world's population. He pointed out that the world's population had doubled in the last 120 years, and he said the best estimates for population increased well that the population might double again in the next 40 years, going from what's at 2.8 to 6 billion people. You have been doing highly original research at the Penrose Laboratory,

and you have some views about limitation of population as a result of your investigations of small mammals. These are perfectly important experiments and conclusions, and I look forward very much to hear you talk about them. Dr. Christian. Well, last week, Dr. Osborn mentioned that he didn't think the population was going to double in the next 40 years, and he indicated that something else was going to happen. And by the same token, I would like to mention that Malthus, who was probably the father of modern population theory, when he was writing in the 18th century, expressed somewhat similar ideas. He was talking about the natural checks of population growth, and he indicated that food, for example, was very seldom a direct check population growth, but the cultural competition that we'd call it today,

between people is what really checked the population and reduced the birth rate. Well, in a sense, what Dr. Osborn and what Malthus was referring to are the things that we've been studying. We are working with something else is going to happen. And to be more precise about it, we've been interested in the mechanisms through which population density, is able to control its own growth. And a number of years ago, there was a die-off of muskrats in this state, and which I happened to witness. And one of the really outstanding things about it was that there was a variety of diseases, which were turning up in these animals that were dying, and some with no apparent disease. Well, this didn't make sense epidemiologically, and immediately indicated that something was wrong with the animals themselves that they were becoming so susceptible to these various diseases.

Well, it seemed logical then, after thinking about it, that perhaps the adrenal cortex was very much involved in this, and investigating the literature and so on. It looked like perhaps there was reason to think that as populations grew, that the competition between animals, social, perhaps for elements of the environment, and so on, activated physiological systems, which would then reduce the susceptibility to disease, decrease reproductive function, and things of this are. And at that time, it looked like the adrenal cortex was a key to this, like adrenal cortex and reproductive function. And we embarked on a program, experimental program, to see if this was true. Now, I should add right now that, for those of you who might not know, that the adrenal cortex puts out hormones that help animals in an emergency or to adapt to a situation,

but at the same time, they also reduce disease resistance, and they produce a lot of other changes. And while there is active at increased activity of the cortex stimulated by the pituitary gland, reproductive function is curtailed, growth is curtailed. So we went about exploring these things at different population densities, and as usual in laboratory work, we took mice, nice, convenient animal to work with. And we'd put animals in cages in different numbers, and then after a period of time, take them out and measure their cortical function, reproductive function, and so on. And we found that in this situation, as the number of animals increased, adrenal function increased and reproductive function declined. So here we have to say that food was abundant, water was abundant, and this was an extensive environment. And so far as we were able to do it, we provided all the needs of the animal in excess of anything.

We watched them closely for this to make sure that they weren't competing for water or for food, and we'd scattered the food and put plenty of it in, and we kept constant temperature, constant daylight, things of this sort. So as far as possible, we removed environmental considerations. And during this experiment, the number of animals was increasing. No, at first we kept the numbers constant, because we'd have a cage with four, one with eight, and so on. And this is an artificial situation, so the next logical thing to do was to put a few pairs of animals in a cage with everything supplied in abundance, and then as the population grew to see what happened. And we found precisely the same thing. To me, one of the most interesting aspects of this work is the fact that it affects the young. And if the mothers are crowded, presumably through the failure to produce milk adequately or milk of adequate quantity, we find stunning of the young.

And their young and Turner stunned it, even though they've been removed from the situation. Defitis also has an endocrine system. Well, no, this apparently doesn't happen in utero. It's something that goes on during the period of lactation, because experiments were designed to check precisely this point. And the stunning took place during lactation. And whether the mother was nursing her own young or the mother raised by an isolated animal, the effect was the same. And when they were in turn bred, the effect was the same. So this was a function of numbers. The numbers reached a seven point where these physiological abnormalities were perceived. Right. And there's sort of a dose effect here. The greater the number is the greater the dose. And you can set up a whole system of responses that represent greater and greater doses as you go up and down. And the doses are numbers. Yes, numbers of animals are out of two each other. Not only numbers, and I was going to get to this point,

it's the degree of social interaction between these animals. The numbers are only indirectly related. You have to think in terms of the total social pressure in a group. And it might be if you had an equal amount of social pressure to use a rather loose term. It might be found in six animals in this situation in 12 here. But by and large, if you expand a population tenfold, the amount of social interaction apparently expands similarly. So the permissible density for our species may vary between species. But for any species, there is a concentration of numbers in which the social tension is increased to a point that you begin to observe these abnormalities. I don't think you can even say that within species, there are limits to find by species differences to be sure. But within species, then you have individual differences. And it's determined by the behavior of the individuals that make up the population.

If you have very aggressive animals about equal, the competition between them will be much greater than if you have wide separation. This brings up the matter of social rank. These animals do rank themselves in a social hierarchy. And these responses within a population are related to the animal's position in rank. In other words, the dominant animal will have the least physiological response. And the man who is on the mouse who is on the bottom of the totem pole will show the most physiological response. And when we talk about populations, we're really talking about the average of everything that's going on within that population. And as you can see, when a population builds up, and you have a dominant boss animal in there that most of the new animals are added to the bottom, so that you are getting the population composed more and more subordinate of animals in the physiological effects are greater. So the subordinate animals show these responses to greater degree than do the dominant animals.

Before you get onto the business of dominance and subordinate role, if you would like to talk a little bit more, I understand that the population limits itself. There is a limitation of population as a function of this is an instance of disease and numbers and so on. Well, all population growth is a function of three things, of mortality, and mortality, and movement. Yes. And what happens as you increase these density effects? You decrease mortality and you increase mortality through the mechanisms I mentioned, increase disease susceptibility, decrease fertility, decrease maturation. There's real inhibition of maturation in these animals. The young animals seem particularly sensitive. Until you reach a point, the population bends over and no longer grows. It's the old sigmoid curve, and it acts as a self-regulating device, and this will occur in a respective food or anything else.

This is a really very, very new and very original view that mouth is me have hinted at it, but this is the first time it has been propounded as a view and as a limitation in populations, and you have seen this repeatedly with animal experiments. That's right. In the laboratory, and we've also worked with a variety of species in natural populations, and, well, for instance, deer and wood chucks. Various species of mice, we did intensive work on rat populations in Baltimore, and we see evidence of this in a variety of the animals in the various zoological herds, for example. What about the characteristics of characteristic diseases in these situations? They're not the normal range of diseases. They're not pneumonia and bronchitis. Oh, yes, it can be. But are they not, I understood you'd say that they were more renal and arterial coronary diseases than any other? Well, we have pretty good evidence, at present time, that there is a real relationship between the density and these animals, at least,

and the development of cardiovascular renal disease. But the details of this have not been worked out, and we don't know the chain of events that lead to this and precise relationships. Furthermore, I think it would be permissible for me to say that we do find a rank relationship in these diseases, too. But these are diseases that are induced in the animal. We don't understand them very well. They're not the usual infectious disease, to be sure. And in these populations, there's real increased susceptibility to infectious disease. And I'd like to point out, before we go further, that this increased adrenal cortical function has been measured directly. And it's been found that when you put monkeys together, there is increased adrenal steroid production. And furthermore, John Mason, down at the wall to read, has put people together under perfectly normal circumstances, and found that there are adrenal secretions increased by simply being put together.

So in total, what you're saying, it seems to me, is enormously important that, from a given pair of animals, as the population increases, that the birth rate decreases, the birth rate decreases, there are lots of births, interutering losses, there are deaths from lack of milk, for other reasons. And then there is a progressive increase in this particular range of diseases. That's correct. To such a point that the population then levels off. Yes, the influence of this is that what you call social pressure, which has some relation to number of animals, density of animals, is, in fact, a limitation in population growth. That's right. And there are a couple things that I should add, though, for completeness. And one is that this does not eliminate the possibility that food could stop population growth. If it entered in and it became short below the self limited level, then it could stop population growth.

The fact is, however, that in natural populations, and they've been studied for many years, it seldom is. It seldom is disease, it stops growth. It seldom is diseases. The per se, in an epidemic sense, a variety of things come in, and mortality from a variety of diseases, both kills animals and helps drop the population. But I think it's important to remember, at least in animal populations, that the basic factor is the decline in births. Yes. But this you actually see, as population increases, the birth rate is reduced. It's reduced to zero. If the population reaches its level enough, there is no reproduction. And there's total inhibition of maturation in all young animals. And it's fascinating, because you can get a whole population of old animals that are there in mature. And then, of course, as they expire, then the population ends. Well, it'll go down to a certain point, and then it's slowly. I see.

Start to recover. But the effects of this density on the animals in the population is a prolonged affair. It's a really profound effect. And it takes a year and a half or two years to get over it, even for small mammals. Partly through the mechanism I mentioned of stunning of the young undoubtedly and things of this sort, which we don't understand yet. I see. Do you want to talk now about the dominant and subdominant? I seems to me this is also sort of splendid analogies. The dominant dominant and subordinate, right? Well, as I indicated, practically all animals set up some kind of a social system. And birds, for many birds, it's territorial, where each bird has a very rigid territory, which he stakes out as his own, and won't allow other birds in. Defends it. This is a definition of territory. It's an area that an animal or bird will defend. And they seem to achieve some self-regulation in numbers through that system. There's just so many territories that can be set up in an area. And then in a lot of the mammals, particularly in house mice and some of the things that we've been working with, they're much more apt to set up the social hierarchy.

As I've mentioned, and this seems to be the governing factor in the population, the behavior of the few dominant animals. And their physiologic responses are accordingly. And consequently, there's this ability to disease, perhaps a development of disease itself. And the dominant animals facing in exactly the same physical environment have dominance over the social environment, and not as susceptible to these diseases as a subordinate animal. Is that right? That's right. And there is a market difference. Well, you can't really separate the physical and the social environment, actually, because the animal is socially dominant, will be dominant over what portion he wishes of the physical environment. Yes, yes, all right. I think I saw in your experiment, the poor, no doubt little mice who cringed in the top of a column. These were the subordinate animals in your experiment.

They were. And the dominant animal goes around once or twice a day and checks up to see that the subordinate animals are all in their proper places. And he nips them just for the past the time of day, I think. He's a fearful tyrant. Do you want to talk about clustering? This is another extraordinary phenomenon which happened because, did you say, after the population reaches about half? That's right. And it's in phenomena we don't understand at all. We know that it occurs and it's a fairly good measure of what level the population is attained and what it's going to attain. But these animals... Exactly. You see clustering? When we see clustering, we know the populations about half grown. And the animals, the only analogy I can think of is that they've been individualists and all of a sudden they become group conscious and they huddle in groups. And all the animals will pile into one small area instead of utilizing the other. I don't know how widespread this is. At first I thought perhaps it was characteristic of mice, but now we're beginning to find that it occurs in other species as well. And apparently this is a quite typical sort of thing.

And it's a real hallmark and behavioral change. But is this an appropriate time to enter the whole subject of human analogies? Or do you wish to speak more about your animal experiments before? No, I think that if I've answered your questions on the animal experiments clearly enough. Well, I just simply see the specter of this curve of population, the limitation of population not by food or water. But simply by numbers, some aspect of density and some aspect of social pressure. And then the extraordinary character of these diseases, which appear at the happy mark and thereafter are characteristic of the population until it flattens out. But the analogy, of course, between animals and humans and urbanism is a consummate interest. Well, it is a specter. I think it's an awful one. But some analogies, I think, can be drawn between the animal experiments and humans. And humans, as I've already indicated, in so far as I'm aware, experiments have been carried out.

The reactions are precisely the same grouping of humans or sub-primates, such as monkeys, apparently produces the same responses that it does in the animals. And I think you have to judge from there on on the frequency with which this would normally occur and whether the person is going to be affected by it. But you haven't started with a breeding pair and built up a maximum population yet, have you with... But you proposed to do this with monkeys. With monkeys, yes. Yes, we definitely do. That has not yet been done. No. Although we do have quite a bit of evidence of this sort of thing from colonies kept at the zoo in other places. And as I indicated, people at Walter Reed have measured grouping monkeys. But analogies with humans must remain analogies at the present time because we simply do not have the information and data to say that this does or does not happen by large and human beings. And I was reading a very interesting paper the other day of Birxen and Stanley's group at Chicago

where they were able to show that cardiovascular renal disease was something like five times as prevalent in rural population as in urban Chicago. Now, these are the stresses. Again, this is the Caught's Eyes ACTH. We don't know. We really don't know. We don't. They're associated, but what the mechanisms of their production are is a subject of a tremendous amount of intense research. And we think they're related to the ACTH, the adrenal mechanisms, but there's a lot else too. And well, the first thing you'd think about if you were comparing a farmer with a desk worker would be well, the farmer is out and physically active and the desk worker isn't. And therefore, this may be a factor, but interestingly enough in this study, they compared various socio-economic groups, job types, and so on within the urban group, and they were unable to relate anything with changes in activity. So to a very real extent, I think that we're concerned that there is something else between urban and rural environments that makes it very real difference in the incidence of these diseases.

Are these heart diseases and kidney disease? Yes, that's right. And it was quite spectacularly more common in the urban situation than the rural situation. That's right. There's high common phrase about urban neurosis presumably, which has some actual basis. It may not be measured. Well, my feeling on the subject is that we simply have not measured the right things in human beings yet. That you have to work within the social unit that the person is living in and measure these factors and see what's happening before you can really talk intelligently. We have never, to my knowledge, made careful studies in humans that would be comparable to the studies we made in a group of mice where we know where their social rank is and we're able to make measurements and so on. I don't know of this having been done. There must be some gross extremes. I mean, surely there are several places in the earth where there have been recorded downstairs of 700 persons per acre. And one would think from the animal experiments, at least in this is an excess.

If this is an excess of any densities you see in your animal experiments, it's surely there are some consequences. I don't think we know what density is for one thing. As I indicated, even in the animals, numbers and the effects of density are somewhat loosely related. It's not a strictly number relationship. No, it doesn't include numbers. It does include numbers. The absence of numbers eliminates social pressures. Maybe some numbers. Yes. But I think to be able to talk intelligently about human densities and human populations, we have to know what densities affect people. What is the effect of pressure in increased numbers that will affect people? I'm sure we'll find them. You're suggesting the stress that we can use this down with qualifications that this stress may occur even without the small numbers and be quite high. The animal experience would indicate that it is also associated to some extent anyway with numbers too. Absolutely. And of course, as numbers increase, you would increase the proportion of the animals that are affected.

But you have, I don't know whether you speak as a scientist or speak as a person. But I think you have very pronounced views about urbanization. You respond very strongly to Fairfield Osborne's prospect of a continuous city from Boston to Richmond, perhaps even to Florida. This would seem to me, you see, the Japanese landscape architect and other scientists, to have some superficial analogies right away. This extraordinary concentration of people, 300 million people in the United States by the end of this century, 80% of them perhaps even more located in urban places. Are you prepared to be unscientific enough to make any speculations about this? Well, I'll speak as an unscientist. And to me, it's appalling. And I have just the drive-in and out on the expressway is a real traumatic experience which is certainly associated with city and urbanity, if you will. And the lack of being able to go out and get away from it is this creeping menace of burying everything under housing development. I think there's a real restriction of individuality of freedom here. I think that people's ability to have an outlet for their emotions is being seriously curtailed.

And I personally think, and this is without data, that this is the mechanism that's going to limit population growth in human beings. And I feel reasonably certain, and again, speaking very personally on this, that we will see the same thing happen in humans that I can see in our animals. I hadn't realized there was just a little information about the analogy of the analogy between the types of diseases you've seen, your mice and other animals and the diseases and human beings. I thought that there was a little evidence in a way to suggest that there were very similar diseases, perhaps produced by similar causes of the high incidence of heart diseases and renal diseases, kidney diseases which you observe as between urban places and rural places, that this might in fact be directly related to social pressures which in turn might be related to density. Well, we think they are, and I didn't mean to imply that there was wasn't similarity in the diseases in humans.

Because this is the most striking thing about the change in the nature of diseases, and over the last 25 years it marked increase in even in the animals and the animals too. But certainly among human beings, the great change from tuberculosis and pneumonia and bronchitis and so on to suddenly this, the disease of hypertension, the heart. Of course you have to correct for age. Yes. And that's two, older population, greater survival and entirely different type of life tables a day than there was 25 years, 50 years ago. They had a biotics of change things so. Yes. But what I meant to imply when I was a little negative about the diseases before is the mechanism of producing the disease. But the relationship exists, but we really don't know very much about how these things are produced. But the presumption is that social tension. We think so. Other groups don't.

Well, we can certainly say that social tension is one of the products of a city. I don't think anybody would argue about this at all. Do you think so? No. I don't think there's any doubt about this at all. Well, the great, the frightening thing is whether or not we're going to abandon voluntary control of a population have this subhuman control. Whether we choose to limit populations to have an environment in which the density or social pressure is appropriate to some optimum living condition. Whether we abandon choice altogether and have this subhuman genetic stress control, which will simply increase the instance of disease and diminish the rate of the birth rate and stabilize populations in this way. It seems a strange in advance for such a modern society that this population would be decided this way. That's a question how modern it is. I'm pessimistic. I don't think people are going to do much about it until the shoe is already squeezing. Whatever we look, planning by catastrophe. Yes. Radiation is the result of radiation.

We decide that our unfortunate byproducts and that we perhaps have got to come to terms with this. We see population in making an enormous impact upon the resources of the world. We have got to call a halt perhaps if there is going to be enough for everyone. Indeed, there is going to be liberty. And here again, we see that we may have the choice of voluntary control of our births. We will concede this power and the subhuman apparatus will assume control. I think that we fool ourselves by the substitution of economics. It is a smoke screen and it is really the same thing. Perhaps we will discuss that at another time. Dr. Christian is enormously illuminating to find out this information. It is a paramount importance and very grateful to you for your information. Thank you very, very much indeed. Pleasure to be here. In the cards against today has been Dr. John Christian, physiologist of the Penrose Research Laboratory of the Zoological Society of Philadelphia.

In the card is chairman of the Department of Landscape Architecture of the University of Pennsylvania, a landscape architect, and a city plan. Transcripts of today's program are available. Thank you very much. Thank you.