In addition to cultural controls acting to maximize fertility, there are important, and often competing, interests of individual families to limit fertility. Unwanted births are dealt with by infanticide in many cultures. Additionally, fertility is regularly controlled by limiting marriage within a culture. Another very important factor in population growth, especially in the tropics, is food availability. Heavy rains in the tropics wash nutrients away, leaving deficient soils. Much of Africa is either too dry or too wet. Africa was, until recently, not densely populated. Since land was available and because more children meant more security and power, a culture evolved that emphasized high fertility, justified by the need for descendants to pacify ancestors. Sub-Saharan (tropical) Africa has the highest birth rates in the world. As an example, Niger, just south of the Sahara desert has a fertility rate of almost eight children per woman while, in the Mediterranean zone, Morocco, just north of the Sahara, but also a Sunni Muslim country, has a rate of only 3.3 children per woman.
Caldwell, Pat and John Caldwell. "High Fertility in Sub-Saharan Africa." Scientific American (May 1990), pp. 118-125
Boserup, Ester. Woman's Role in Economic Development, pp. 15-52
Van de Walle, Etienne. "Fertility Transition, Conscious Choice and Numeracy." Demography, 29, pp. 490-496
Bledsoe, Caroline, Fatoumatta Banja and Allan Hill. "Reproductive Mishaps and Western Contraception: An African Challenge to Fertility Theory." Population and Development Review, 24, pp. 15-18, 20 and 33-45
Daley, Suzanne. "Screening Girls for Abstinence in South Africa." The New York Times, 17 August 1999
January 27, 2009
Professor Robert Wyman: I see this is largely, but of course not exclusively a female class, and I know that's because of the reputation of the class as being very tough on men. What have we learned about men so far? They're violent, they contribute only a speck of protoplasm to the next generation, they help hardly at all in child rearing. In the Tuesday reading you found that they're even afraid of their wives, and on Thursday how many of you did the reading about the Na? What do they believe about man's role in reproduction?
Professor Robert Wyman: Just do gardening, they just water it. That the baby comes totally from the woman's substance and men just have to water it occasionally. As you know water is water, is water so it doesn't matter which man waters it, and they have a very promiscuous sexuality. Feeling very sorry for the males, and I don't want them to go through too much of an ego crush, I have to tell you that some cultures indeed give credit to males in all of this.
In particular, the Barre tribe of Venezuela, who are one of the isolated tribes in the Venezuelan Amazon, and they believe that a woman's body is just a vessel and that men do all the work of reproduction. The only limitation--the very first act of sex must be between husband and wife. They have marriages but the first copulation has to between husband and wife because that plants the seed, and it's very important that the seed belong to the husband. Once he has planted the seed the growing fetus is not done with male need, so the fetus obviously has to be nourished, it's keeping to grow has to get the nourishment. It doesn't get the nourishment from the mother, it gets it from semen.
The fetus needs a constant contribution of semen all along to make it grow. The Barre claim that this is very hard work for men to support a pregnancy. They have to have sex all the time to do this and the women are worried about wearing out their poor husbands. Now this is not just this cultural--just dreaming stuff up, this has real empirical basis and the Barre say, 'look it's obvious, women grow fat during the pregnancy, while men they grow thin from all their work,' so they have good reasons for believing what they do.
What's the solution? Well they ask other men to help. The husband--they don't want to wear out their husband, he's got to do a lot of stuff. They ask other men to help, and it's strange, even though it is such hard work, the men seem quite willing to pitch in and help. It's very nice, it's very heartwarming that men can, at least temporarily, stop all this male/male competition and help another guy when his wife needs a little nourishment.
When we get to discussing the reproductive biology that relates to abortion much later in the course, you will find that actually Western scientific knowledge does not go much beyond what the Barre understood until about 1840 and well into the nineteenth century. That's--until then what--how a fetus was formed, what the male contribution was, what the female contribution was, was a big hot argument. Some thought it was all woman, some thought it was all male, and they just had no idea. Human fertilization was not discovered until 1840 in the West. We were having the same argument that the Barre do.
Furthermore--anybody know approximately how long it takes if a human couple wants to get pregnant how long it takes on average? It's more like five months. You'll hear--again when we discuss abortion you'll hear the reasons for that. Actually, in that five months, the husband gets the first copulation, but thereafter a lot of guys have to help, so by the time five months rolls around, the average for getting impregnated, an awful lot of guys have had their seed in there. Again, in actuality, paternity is totally uncertain. That is it comes right back to the chimp story that the community hangs together, one reason because no one knows anything about paternity.
Okay, last time I was describing how all cultures have mechanisms so that families in fact only have about half as many children of which they're biologically capable. Remember we did this calculation and we found this 69 number and so forth. I was in the middle of a story and actually it's in your reading. It's reading for last Tuesday about the Mae Enga of New Guinea. They believe, the males and females both believe, that the sexual fluids and odors and emanations from women are dangerous and even lethal to men. Hence, the men are terrified of having sex with the women.
Now you read this in your reading and you may again throw it off as just one of these cultural practices of primitive people, and that's not the way you should approach this class. You should--on the other hand ask how does such a practice arise? What are its roots? How does it help their culture to survive? The theory being that most of the things that people are doing have some role in helping them in a difficult world.
As you know, in chimps as in most human societies, they're exogamous, that instead of the male going out to mating, the males stay together in one community, and the females go out to mating. The same is true with the Mae Enga, and females transfer groups. Also we know that, as in chimps, in New Guinea each of these tribes is always at constant warfare with their neighbors. They are truly enemies.
When women are exchanged between neighboring communities they don't travel very far; they'll get killed if they travel very far, so the only people they know are the neighboring communities and someone from this community will marry--will get a woman from a fairly neighboring community which means getting a wife from their enemy. That's again very similar to the chimp setup.
The Mae Enga are very much aware of this, as you've read, 'we marry the people we fight,' and there's a lot of distrust and fear of the enemy wives. Because of that, the husband does not sleep in the hut with his wife and children but sleeps in the men's hut. It's a male bonding sort of thing rather than a male/female bonding sort of thing. Apparently culture has used this distrust of the wife, this fear of the wife, as a mechanism for restricting sexual activity.
Of course, the Mae Enga like every other human has tremendously strong sexual drives but they're living on very fragile ecological land and they can't overpopulate it, so they have to have some mechanism of tamping down reproduction. This is one of the mechanisms; the men don't even sleep in the same house with women. It's a rare event when the women--when they visit the women, a rare and dangerous event and that keeps the birthrate down. Now in the reading, there's a third point that's very easy to miss because it's just one little phrase and it talks about how dangerous sex is.
You remember who it says is particularly vulnerable? The young males are partic--she remembers that. The young males are particularly vulnerable to these dangers and so their health will be undermined, not only by frequent intercourse with women, but even by frequent contact with women. Of course the older men are rather immune; as you grow older you gather immunity to this. Now we know younger males are driven very much sexually, older males it cools down somewhat, and so here's this cultural belief counteracting biology. It's the inverse of what you would expect. You would expect the younger men to have a lot of sex and the older men to sort of tail off on it, but what does it insure? It insures the control by the older, dominant, mature men. Again, it goes right back, it's the Mae Enga; it can be perceived as the Mae Enga version of dominance hierarchy in the chimpanzees. Well there's an extended description of this in the reading which is wonderful, which I hope you've already done.
The--so far I've been describing how culture, communities push fertility up, because, if you don't get on average eight or so children from each woman, the culture disappears, but they also have to push it down because if reproduction goes too wild the children just die. I showed you data about inter birth interval can't get too short or the children just die. Individuals--that's all from the community perspective so far--but individuals, and individual families, they have to adjust these rules. There's these cultural rules which are usually very strongly enforced, but individual families have--each has a different situation and they have to adjust the rules somehow to cope with their individual situation.
Of course this leads to conflict between what an individual or an individual family wants and what the culture says you must do. One of these examples, I mentioned last time, is post-partum abstinence, that in many parts for instance of Africa, after a child is born there will be three years in which a woman is not supposed to engage is sex. Obviously, primarily a mechanism for spacing births, so that the children stay alive and the woman doesn't get killed from too much strain on her resources.
Now if you think about that a little bit, you have a young woman, young husband, marriage is fairly young generally, the husband will be a good bit older but still young and he's facing--the wife has a kid, he has a kid, and the wife is face--the husband now facing three years without any sex. What is he going to do? He's going to want to take a second wife or maybe visit a lot of prostitutes and spend money. That's something that often the wife--the first wife or second, or third, or wherever she is in the chain, will not want.
Sometimes she does want that and we'll talk about polygamy later and why women very often choose to be in polygamous relationships, but very often she won't want him to take another wife unless he's got a lot of money he just won't be able to help more than one wife. What does she do? She has to figure out of way of resuming sexual intercourse but not get pregnant. What does she use? Contraception; so surprisingly in Africa, one of the major reasons for the people accepting contraception is not a desire to reduce fertility as in most all the rest of the world, but a desire to resume sexual relationships without getting pregnant.
She has to do this not only to protect herself because she knows that if she has children too often she wears out her body, and there's a reading on exactly what certain groups in Africa--one group in Africa considers this wearing out of the body. Also, if she gets pregnant right away the community knows that she and her husband have violated the taboo, and there's very strong social proscriptions against--proscriptions against violating the taboos, so contraception which you take privately is sort of the perfect solution for women wanting to return to sexuality but not to get pregnant.
Another aspect which we already--I just mentioned of control of fertility is what I call gerontocracy, ruled by old folk. The old folk can monopolize--the older men, can monopolize the sexual activities of younger women, and because they're not as vigorous shall we say that reduces--is one mechanism for reducing fertility. One of the ways which came up in one of the sections is the idea of bride price. Dowry is more commonly known is where the wife's family pays the husband, the husband or the husband's family when the wife gets married.
The reverse of that is called bride price and it's much more common then dowry in Africa. In this case, the man or the man's family, or the man's side must pay the father of the wife for the--before he gets the woman. It's sometimes in the West considered buying the woman but it really is not a buying situation. These bride prices can be very high and a young man usually does not have the money to buy a bride. Who controls the money of the village? Who controls the resources? Why the older men who are the village elders and control everything.
They dole out very sparingly the bride price to allow men to get married. This is like among the Maasai of Kenya, very tall people with a lot of popular press about that. And because the young men are not getting married and there's roughly--equal numbers of males and females, that leaves a lot of excess young girls, fertile young girls, and who gets them? The older men go polygamous and they can have several wives, but remember for every man who has more than one wife that means there's another man that has no wife whatsoever.
When you read the ethnography of this, the anthropologists who go in, it's very clear that the young men are held in a state of sexual frustration and the young men have ways that they talk to each other, and they are just on the verge of rebellion. The strategy of the older guys is to keep these young men just below that--keep as much sex for themselves but keep the young men from getting together and rebelling. They co-opt what we now were--they co-opt the young guys when the older more dominant of the younger guys, when things start to get out of hand a little bit, we now have bride price, and you can go and get married and that co-opts him and takes him out of the cabal that might start a small revolution.
This is all going on subtly, often hidden within these communities. These are large--affects this whole polygamist situation. In much of West Africa almost half of all wives are in polygamous marriages and that means about half of the men have no wives whatsoever. And in the 1920s--so a lot of what I'm describing is traditional culture and we all know that the whole--everywhere in the world is changing very rapidly, but you can't understand where they're going unless you know where they're coming from. In the 1920s, 40% of the men got to be 40 years old without having been able to marry, so that's almost half your population without "legitimate sexual outlet" until they're 40 years old.
Today, even today, and this is from a few years ago, the median age of marriage is still almost 30 and great pressure and power from the older guys is necessary to maintain a situation like that. They also leave sort of a pressure valve on this whole situation that they don't totally suppress the sexual activity of young men. They turn a blind eye to a fair amount of prostitution; that's reasonably accepted, and to "discrete access to the younger wives of older brothers or even of their fathers." Again there's the dominant males who are sort of officially in charge, but there's a lot of extra stuff going on. Again, it's the great ape kind of pattern. Even today, this story of the dominant older males getting the most sex has by no means disappeared.
Now it gets a little more unpleasant because this control of population by pre-[modern chemical contraceptive societies] is very often post-pregnancy. We've described so far all kinds of pre-pregnancy mechanisms reducing sex, etc., but women still get pregnant and very often they or their families decide that they can't have these children. A lot of this is post-pregnancy population control and even--and post-natal also.
Abortion and infanticide are common among--or have been recently--among almost all human groups. Different communities and different individual families have a different amount of resources and they must match, in some way, match their fertility to the resources that are available.
This is a very discussed and studied topic in population circles, so a few years back Karen Mason, who was president of the Population Association of America gave a wonderful quote about how people adjust their family size. "Parents kill their infants, abandon them, neglect them in the hopes that they will die, give them into the care of wet nurses where they usually die, sell them, give them up for adoption, marry them off at a young age, loan them to other families for fostering, send them into service, or into other households, send them to the military, the merchant marine, prostitution, or send them overseas as migrants."
All of these are very standard mechanisms for individual families controlling the number of children that they have to rear. In Western culture it's certainly not unknown, the founding myth of Jewish people? Moses. What happened to Moses? He's a baby; he's thrown in the basket, floated down the Nile. You go to China, a very standard way of getting rid of children--everywhere--every culture that has a river, babies are put in baskets and floated down the river as a way of getting rid of them. Of course the Bible story that the Pharaoh's daughter finds this baby floating down the river and you can believe that or not, but obviously, that sort of behavior of putting a newborn infant in a basket and floating him down the river was apparently extremely common at that time, so the story wouldn't have been surprising.
Student: There is one minor difference. Moses mother didn't want to kill him, on the contrary, she wanted him to survive.
Professor Robert Wyman: That's the story.
Student: Yeah, because the Pharaoh would have had him killed otherwise--as all the Jewish boys were killed.
Professor Robert Wyman: Yeah, if you read the original--you're completely correct, if you read the original story it reads as if 1. She wanted to keep him alive and Pharaoh was going to kill them all, and 2. that she saw the princess sort of on the other side of the river and thought that the princess would see it, so you can interpret the story as you want, but it's a very standard multi--many, many cultures, cross-cultural mechanism of infanticide and there it appears. What is the founding myth of the Roman people?
Students: Romulus and Remus.
Professor Robert Wyman: Romulus and Remus; what's the story of Romulus and Remus?
Student: Raised by a wolf.
Professor Robert Wyman: Raised by a wolf, so Romulus and Remus twins--we'll talk about twins in a moment, left out on a hillside; standard form everywhere in the world of abandonment, you know some animal will eat it, but in this case the wolves didn't eat the babies, they suckled them and they came up to found the Roman Empire.
Sure, so it's quite interesting how many of the founding myths have this abandonment story in them. With respect to twins, for instance, the Uwa tribe who were very traditional, isolated people in Columbia and South America, when they have twins they abandon them in the forest or toss them into the rivers, and their cultural belief is that they bring bad luck. Of course in this situation where a mother is undernourished she probably is going to have difficulty bringing up one child, and two is just kind of impossible.
If she believes, or the culture has sort of over history figured out that the children are going to die, one or both of them, then the amount of resources put into trying to raise a child who you know is going to die anyway is just not acceptable. Of course none of this is a conscious calculation. If you ask the people why they're doing it, they always give some kind of religious or mystical, or magical kind of interpretation to this behavior, but we can see it as one of the mechanisms for having families limit their fertility to what they think they can cope with. In addition to controlling the rate of reproduction, the control of population continues after birth. We haven't talked about abortion, but during pregnancy via abortion, we'll get to that later.
Societies are also really very careful about controlling the number of child bearers and they--in England, for instance, and we'll talk a little more about this at a later time, people couldn't marry. The peasant on somebody's estate could not get permission to marry unless he had enough property to support a wife and children. Very often this meant that he couldn't marry until his father died. The father was living in the house and he just had to wait until the father dies and then he was owner of this property, then he could take a wife.
Well the father dies when the guy is maybe 40 or late 30s, and so that cuts down his reproductive potential a lot, and of course the wife that he marries has not been married up until then, so her reproductive potential has also been knocked down. In many ways, since the fertility of a society basically does not depend on the number of men, it depends primarily on the number of women. We saw this--last time we discussed the permissibility of polygamy even with limitations when a lot of men are dying in war, but this happens in many, many situations.
In India, as you know, traditionally it's almost never practiced nowadays. A man dies, what happens to the wife? Sacrificed on the funeral pyre. Again, there's all kinds of religious and cultural explanations for it which the people will tell you, but standing back from it among other things, it's a way of controlling the birthrate of the population.
Sometimes in a single geographical setting you can see the two different things working together. The Mae Enga, which you've already heard about in New Guinea, they live in an overpopulated territory. They are pressing up against the ecological limits of their resources. The women are severely degraded; funerals are held to honor men and pigs, but not women or children. If a husband dies, if a man dies, his widow is strangled within 24 hours of his death.
On the same island, New Guinea, the Fore people have a different problem. They have kuru, which we now call Creutzfeldt Jakob Disease, a prion that destroys the brain so they have a very high death rate and their territory is quite under populated; they have great difficulty in getting enough people to stay alive. In that culture, where everybody is scarce, they mourn women and children as much as men; they encourage premarital sex, and widows are not killed but immediately courted for remarriage by the men. Again, this is a society when you're way below the limit, then you want to keep a woman's womb full and you want to keep them reproducing.
I've told you this mechanism for reducing the number of child bearers is severe, very severe around the world, and I mentioned and you'll hear it again, that the estimates that there are by various mechanisms of discrimination against women, there's a hundred million women missing in the world and this is a big part of the global control of population. We've seen some people and a lot of the popular discussion thinks that fertility control, contraception, all that is a new thing that's burst in 1960 or something when the pill was invented--that it just burst on the world and some people think it's wonderful and some people think it's immoral, but in fact, cultures have always had mechanisms for controlling their fertility. They've often been more brutal then what we currently have.
I want to shift gears a little bit. It follows along the following way: so we've been talking about the way people regulate their fertility. What is the main limitation on fertility? Well it's often food, and food depends on how much land you have. Most of what we read in history and what we're used to thinking of human society has to do with very crowded places from Europe, or China, or India. In historical times all of these places have had very high--historically compared--very high, even dense populations. In all of these cultures you have masses of peasants without any land, landless peasants, called land hunger, everybody wants land and there isn't land for it, they fight over land, if you manage to own land, you're going to be very rich from land, you don't have to work it yourself, there's always plenty of landless peasants that can do the work for you, and so forth.
This is pretty much true of--pretty much the characters of recent human history, but for most of human history that was not true at all, the opposite was true. The world was open and there was plenty of land available. We were not a numerous species; we had almost no population growth rate, and so what was scarce was not land, land was plentiful, but what was scarce was people to fill up the land.
Cultures have been aware of this problem, as well as the opposite problem, but this problem for a long time, so one of the great Chinese philosophers, Mo Zi (Mo Tzu) fifth century B.C. wrote, "What is hard to increase?" He's talking about politics and everything, "Only people are hard to increase." He argues--he says that there are policies which can increase population. "The kings of old required that all men marry by the age of 19 and all women marry by the age of 14. Now those who want to marry early marry at 20; those who want to marry late, marry as late as 40. We can expect two or three more children to survive if we were to reduce the age of marriage. Through universal marriage we should be able to increase the population size." This is his advice to the rulers on how to increase the population in their territory. There's plenty of land, that's not a problem. They have to be strong because there's neighboring warring states, they're always fighting with each other, if they don't have a big population their neighbors will come in and wipe them out.
Of course this idea that the government should be an agent of control of the population again has not disappeared; China does it now. In the old days they wanted to use the government and did sometimes use the government to increase the population. China now wants to use it to decrease the population, but it's the same idea that control in one way or another is important for every society.
In this--the rest of this lecture, we'll see how long it takes; we're going to talk about under population of places. The examples are largely going to come from the tropics, and especially we're going to talk about Africa, and that is because until recently the tropics have generally not had a dense population. They have been what you might call under-populated. People were scarce. Up to now we've been talking about--we talked about biological determinants of population size, of reproduction, we've talked about cultural determinants.
There's another whole big factor: geographical determinants. And we're going to talk about three very important geographical determinants of population size, and largely we're using the tropics as an example of this. The tropics generally have low agricultural productivity. The great granaries of the world are not in the tropics. They have parasitic diseases which are endemic, and geographically they're often isolated from the rest of cultural worlds.
This is the--just a general map of Africa and what you see is, this is very standard, here is the equator and--I'm sorry here is--no this is the equator up here, so what you have is in Sub-Saharan Africa, well in all of Africa, you have in the center a rain forest. This is the very traditional jungle and it's flanked north by the Sahara Desert, south by the Kalahari Desert. Then here is another green zone right along the ocean and the very north, this is Tunisia and Algeria, Morocco--just the coastal sections of Africa are green, they have rain. We're not going to talk about North Africa because that's included in the Mediterranean world, just culturally that the Sahara Desert divides.
We're going to talk about Sub-Saharan Africa. You may note that these deserts continue into Saudi Arabia, then into the Sind Desert of Pakistan and the Rajasthan Desert of India, and then the Himalayas interrupt it but you get the Gobi Desert up here and it continues across and in the Americas there's the Amazon around the equator, a very dense jungle, and what's the desert to the north of the Amazon? The Sonora Desert of Mexico, New Mexico, Arizona, that desert is in the similar geographical position to this, it moves up and down.
What's the southern desert in South America? The Atacama Desert of Chile and you go over the Andes and it's not quite as desert but it's the Pampas, which is a very dry region in Argentina, so all over the world you have this--a central zone around the equator which is extremely wet, flanked by desert zones, and then once out of the desert zones you get a moderate rainfall again.
Quickly, the reason for this is quite simple. This is the tropics, heat comes down, the hot air rises, it's the hottest part of the earth, so the hot air rises, bringing up the moisture from the tropics, as it rises it cools, what happens as hot air--hot moist air cools? Rain, so this is a very rainy region. Now the air has risen, it's dropped out its moisture, it's dry air, the air that continues to rise pushes it away, so it goes either north or goes south, and it now by the time it reaches somewhat farther away it's cooled a lot, it's dry because it lost its rain, so now you have cool dry air, and because this region is sucking air back in there's a little bit of a vacuum, the air falls back down as cold from being up here, cold dry air, and you get the desert regions.
They happen in the north and they happen in the south so you get deserts here, and you get deserts here. This is just a characteristic of the whole world, and of course this is interrupted by oceans; this is interrupted by something like the Himalaya Mountains so there's a lot of-- it's not a perfect schema but it explains an awful lot of the geography of the earth.
In this schema, as I've just showed you, in Africa, look how much of it is taken up with that schema. It's from here, from the north edge of the Sahara Desert to the south edge of the Kalahari Desert. It turns out its 97% of Africa or something; 93% of Africa lies in one of those regions; a very wet jungle or too dry and you just have a very thin region here, and some region here, which gets some of the monsoon circulation of air, of warm air out of the ocean.
We have the image of the wet tropics anyway as extremely lush and fertile and you think what a wonderful place for farming. It's a tropical paradise. Actually nothing is farther from the truth; the tropics are generally very difficult to farm and if you do farm them, they're very poorly productive regions. Why is this? How many of you are aware of that, that the tropics are not good for farming? All you Forestry guys ought to be aware of this. The reason is that the soils are very bad and they're bad for a number of reasons.
Well let's go back a little bit. Plant growth is very rarely limited by sunlight. What the tropics have is plenty of sunlight but it's very rare that that is the limitation on plant growth, so the most productive part of the world is in terms of bio-productivity? The ocean around Antarctica--very, very cold region in terms of intensity of sun, every part of the world gets the same number of hours of sunlight in a year, but the intensity around Antarctica is very much less, so there's very little sunlight, yet you get these tremendous algal blooms, the krill eat them, the whales eat the krill, and it's a tremendous productive region. Why?
It has nothing to do with sunlight; it has nothing to do with temperature. You have Antarctica, the continent of Antarctica, which has rock down below it, it's not like the North Pole, there's rock there and the glaciers slide down to the sea and they grind the rock. Where the glacier is coming--falling into the sea, underneath is a layer of what they call glacier flour and that's ground rock, falls into the sea, fertilizes the sea, tremendously valuable--tremendously nutrient rich and then that circulates up the west coast of Chile, for instance the pacific coast of Chile, the Humboldt current you may have heard of, brings up all these nutrients and the richest fishing banks in the world are off Peru where the Humboldt current comes up and brings all these nutrients to the surface.
All over the world nutrients are almost always what limit agriculture. Well what's the story in the tropics? The soil may have started with a lot of nutrients at some time back, but the rains come, a huge amount of rain, and what does rain do, washes the nutrients back away. In most places nutrients are recovered by several mechanisms. One is by mountains being eroded down, that the mountains erode. In February, I was in the Peruvian Amazon and you're sitting there right in the shadow of the Andes and the rains come into the Andes, erode the rock, and parts of the Amazon have rich water flowing through it with the Andes nutrients. Most of the Amazon is flat, does not have any runoff from the Andes Mountains, infertile as hell, no nutrients there.
How does the jungle--so you have this nutrient poor soil, if you go there you'll see the soil is extremely thin. You take your boot and you kick it and a few--an inch or two and there's no soil left and if you look at the trees, what do the roots of tropical trees often look like? These huge things because there's not enough soil to support them on deep roots, there's nothing down there, so they spread out and hopefully stay upright because with these huge, huge buttressed kind of roots. Everything is telling you, if you know how to look at everything, it's telling you that this is thin and poor soil.
Nevertheless, there's all this biomass in the jungle and the mechanism is that the whole floor of the jungle is covered with a fungus, with a fungal mat, when a leaf falls and it's wet, and so then it's never--cannot fall far from a fungus because they're everywhere. The fungal hyphae, the sort of root of the fungus in a sense, invades the leaf and very rapidly sucks out its nutrients. What does it do with those nutrients? Well one end of the fungus is attached to the decaying leaves and other stuff that falls down. The other end is attached to the trees, and it gives these nutrients to the trees. Why is it so generous? Well the trees must be giving something to the fungus.
Well the trees are up there in sunlight. The jungle floor is dark. The canopy of the forest let's very little sunlight in, so they can't photosynthesize down at the bottom. It's--there's not a lot of grass and stuff under jungle trees. The trees make the sugars through photosynthesis, they send them down, pass them to the fungus, the fungus decays and everything else sends the nutrients back up into the tree. It's a wonderful cycle and so basically all the nutrients are up in the jungle canopy, up in the forest, not in the soil.
This stuff, this decaying vegetable matter is the source of fertility and you measure how much of it there is, and the productivity of the soil depends very closely to the percent and depth of the humus, this stuff is called humus in the soil. In tropical soils it's less than 2% of the soil that things live in is humus. In temperate soils it's always over 10%; in upper New York state or Ohio it's 10% to 12%, and the richest Iowa farmlands it's up to 16%. So you can see the productivity of Iowa is just going to be--just from the soil consideration--there's going to be an awful lot greater than the productivity of the Amazon.
Another thing is the rapidity of decay aside--anything that the fungus doesn't get, which is rare, decays by bacteria and maybe other fungi that don't feed the trees. It's hot, it's hot all the time in the Amazon, and what does temperature do to chemical reactions? Speeds them up, so for every ten degrees warmer the chemical reaction in general goes twice as fast. In a jungle floor--in a jungle you'll have maybe 30 degrees higher than New York state, than Ohio, or Iowa so that's two, four, eight--decay will go eight times as fast as in say New York or in my backyard; to say nothing of the absence of the winter where decay basically doesn't happen at all.
I know I make a mulch pile and it takes four years. When I put in a leaf, four years later it's down to good soil, and then takes more years, I don't know how many before that turns all back to carbon dioxide and water. The whole thing is organic; the whole thing eventually goes away. In a jungle it happens much, much more quickly.
To summarize all this, this is--you've got to have some biology in this course. What is--which is more fertile, the Sahara Desert or the Amazon Basin? The answer is really surprising. There's a quote, "Annually millions of tons of dust from the Sahara are blown by the northeast trade winds, thousands of kilometers across the Atlantic Ocean. There they settle upon the Amazon. Some scientists suggest that this is one of the major sources of soil nutrients for the poor soil of the Amazon." It's really--and not a mild situation; it's very extreme, if nutrients from the Sahara can blow a few thousand miles and drop in and be a very significant source of nutrients for the Amazon.
Now, what happens if you try to farm this place? Try to farm in a jungle, what do you do? Well you have to chop down the trees, right? Now mind you, I told you that the forest floor is moist and dark, and if any of you have been there, you'd know that it's very striking. You're not boiling at all. Now you cut down the trees; the sun now beats down, the tropical sun can be quite brutal and it dries out the soil, it bakes the soil. What dies? The fungi die because fungi need coolish and moist environment. They die, your means of recycling nutrients is gone; the soil has very little nutrients itself.
What have you done with the trees that you chopped down? If you're a commercial agriculture place you ship them down river to a saw mill, so the nutrients that are there, they're taken away. The secret of what's called Swidden agricultural, slash and burn agriculture, is that yes they do chop down the trees but in a very local, very small plot of land, and they burn the trees in place and that puts the ash as the mineral nutrients which are so missing and that fertilizes the soil. It's not wonderfully efficient but it does work if you keep your plot small because then the fungus, which is killed there, can reinvade from the surrounding trees.
You start doing commercial farming with many, many acres of spread then there's no way that soil is going to regenerate. How does this work out? For instance, in the Yucatan of Mexico, the Maya lived there for a very long time. In the sixteenth century, a Franciscan bishop Diego de Landa, who was--he wrote everything, everything we know about the pre-colonial Mayan existence comes from him. The Yucatan, this is from him, "The Yucatan is the country with the least earth that I have seen, since all of it is one living rock, and has wonderfully little earth." When you read all these chronicles they always are--they're speaking always of famines in the Yucatan because there's so little productivity and how do they avoid the famines, and this is again before the Spaniards came. They take care of their--they have exports which they exchange for food from better regions. What do they export? Honey; which you don't have to farm, salt which you don't farm, and slaves.
That's another use for "excess people" and controlling your population, you sell them as slaves. You look all over the pre-modern world and of course you know it's not gone in the modern world, slavery is a very big thing and a very big part of what happens to population. We'll talk a little bit about that later. Well let me say it now as long as the topic came up. What is slavery a response too? It's very relevant to this lecture--under population. You don't have enough laborers so you import slaves. In the middle of Europe, where you have teeming populations, or India, or China, are you going to have an awful lot of slavery? No, there's no land for them to be utilized.
Slaves get used, like in the Roman Empire, not as farmers; there were hordes of Romans, peasants that would love to have some land to farm. They're used in the mines; there were household slaves, sex slaves, in the mines. The Arab countries took a lot of slaves through Madagascar and continental Africa; household slaves, sex slaves, somewhat in the mines but they didn't have that many mines. Slavery is a response to under population. Where do you get huge slavery? When you discover the new world and how you have this very thin Indian population in these worlds, largely because we killed them with diseases as you either have read or will read.
You have an under populated--two under populated huge continents with much good land, you first in Western--in history first you try to enslave the Indians, the Indians don't do very well, they die out, so you stop that and you import African slaves who manage to stay alive. Slavery itself is a response to under population. It fits exactly into what I am talking about. Wherever you see massive slavery you're going to find under-population, you're going to find areas of land that have nobody on them, and someone can, by military force, capture people and force them to work for themselves. There's many other reasons why the tropics are hard to farm. Where are the grain belts in the world? What do you know about--where is grain grown? Where is the really rich places? Anybody?
Professor Robert Wyman: U.S., where in the U.S.?
Professor Robert Wyman: Midwest, upper Midwest, Iowa, Kansas, Minnesota. Does it go north of the U.S.?
Professor Robert Wyman: Yes, Saskatchewan, Alberta, way the heck up there, you have this fabulous production of grain. You see pictures of northern Saskatchewan in Canada with the big grain reapers. China, where are the great grain fields of China? Wheat--up in Manchuria, goes up the northeast of China, is all grain, all wheat, way up into Manchuria, and Manchuria goes up it's more or less the same as Alberta and Saskatchewan.
In the south you don't get your great grain growing regions in the tropical region, certainly not in the desert regions. You get them--Morocco, for instance, has very productive agriculture right on the coast where it's a wet region. That's not very far north, and down in South Africa, and Africa just doesn't go that far south. In South America you get it down in Argentina, so again--so there's something that agriculture gets more productive the further north you go, with a limit of course, it doesn't go into the tropics. Why should that be? That goes contrary to our expectation.
Again, the reason is biologically rather simple. During the daytime, plants take in the sunlight and make sugar, make energy. They also respire, they also have to run their own machinery, so they're also using energy, using sugar all the time, they use it day and they use it night. Now the sun goes down and photosynthesis shuts down, but respiration continues, they have to keep themselves alive at night just as we do, we don't stop breathing when we go to sleep. The ratio between daylight and nighttime, how many hours of daylight and how many of nighttime is a very important factor in plant productivity. In the tropics what's the ratio of daylight to nighttime the whole year round?
Professor Robert Wyman: About 12/12, about equal. What is it up in Saskatchewan or Manchuria? Daylight, daylight, daylight, very little nighttime. The plants have so many more hours in which they're photosynthesizing and much smaller amount of time where they're not photosynthesizing but still respiring. That's one big factor why you get these grain belts going up north. Also temperature, how much energy does it take you to just keep yourself alive? Well we've just said, all chemical reactions go--every ten degrees they more or less double, so respiration plants the warmer they are, the more respiration they have. At nighttime it's still warm, so everything is working rather fast in the tropics.
In Canada, it's a lot of sun during the day, but it cools off at night, and so respiration is at a very low level. The productivity of a plant is the balance between its photosynthetic productions, it's production, and its respiration, use of that produce for its own purposes. There's a big difference in the ratio in the north from Iowa to Saskatchewan, or from the Yangtze up into Manchuria, that ratio is just much better than it is in the tropics. We won't continue too much with this.
We can also talk about the diseases that--in tropical regions you get Malaria, you get a whole bunch of insect borne diseases, tsetse flies carry sleeping sickness, etc. One to two million Africans die of Malaria every year and that's about the same number as AIDS. Malaria and Aids are about equally devastating to a population. It's about 11% to 22% of all deaths in Africa are Malaria deaths. Yellow fever, Leishmaniasis, bilharzia [Schistosomiasis], roundworm, hook worm, the number of parasites that live in tropical regions is enormous and very often they kill humans and make--they can't go in there to farm because they'll die.
Why are the tropics so much more susceptible to disease, this kind of disease, insect born stuff than the northern regions? It's a simple factor, winter. Winter kills insects, it kills them massively, very hard for insects to not freeze to death over the winter. Tropics don't have winter so it's a whole class of problems; they dry out, the winter is extremely dry, they go desiccate and freeze and it's very--organisms kill them. In the tropics, nice all the time, insects just have a good time and they can evolve, use their evolution to attack animals and people much better. All of this really adds up and geography counts and people have to adapt to the geography.
In this case the adaptation is to an under-population and I'm going to show you--well just to give you an idea of how densely populated Africa is or isn't, here are some European--some non-African places. Netherlands is one of the most crowded in the world; 1,011 people per square mile. Japan: 870, but that's--in terms of arable land Japan is mostly mountains. They just have very small areas where people can land, so to compare the Netherlands are all flat, people can live everywhere. But if you want to compare this to that they're probably--per arable land where it's more crowded than the Netherlands.
Belgium same as here, India, China and again China is the same thing, they have the whole Himalaya Mountains in the west, the whole huge dry regions in the north, Tibet--Mongolia and the northwest regions so this is way an underestimate for China. Mexico has a lot of desert, looks fairly under populated, but a lot of that is because you got desert space.
Now you go to Africa, Nigeria one of the most densely places is 346, that's not extreme. Since Nigeria it's all--no mountains, no deserts. In principle all of this land could be used so that's a real number, whereas, the Chinese number you should multiply it by a factor of three, it's about a third of the Chinese land that's actually arable, so China is ballpark 1,000 and Nigeria is about a third of that. Kenya is down--again Kenya is pretty much all livable, and they have a low population. Madagascar's all livable. Angola is all livable. Mali and Niger have deserts so those numbers have to be corrected. Congo doesn't have deserts.
The point is that the population density in Africa is a lot less than other places that we think are--we don't think of Holland as overpopulated, but in terms of just a simple people per arable land it definitely is. Africans, again, we're looking at something that has a big historical component. I have to be careful when I'm talking--what era of time I'm talking about. These are modern numbers I'm going to show you but they reflect people's attitudes that have changed that are appropriate for some time in the past, and only change very slowly.
This is Morocco on the coast, this is not part of the Sub-Saharan Africa zone. This is very integrated into the Mediterranean zone. Almost everything you can say about its culture, it's really a Mediterranean culture. Look what's happened to its fertility over time. It was very high, more or less equal to every other place, 7.2 children per women and that stayed the same, but in recent times it's gone down to less than half of that, 3.2. This is not the most recent data. I wanted to show you a little bit older data. It's gone down even further. That zone of North Africa, Tunisia is at replacement fertility level, and North Africa has characteristic of this.
Now I'm going to show you the next country to the south which is Mali. I'm sorry Niger, because Mali is also there, but Niger is--when you go south you cross the Sahara Desert and you're in Sub-Sahara and Africa. Now look at its fertility, this is even a little bit later in time, and look at its fertility rate, it hasn't budged at all. It's again, eight--seven, eight children, middle, eight children, and it ends up here even more then it was in 1950s. It has not changed. The fertility rate has not responded to whatever it is about modern times and we'll talk about it a lot what has caused fertility to go down.
Now one thing you can say is how many women don't want to have any more children, and that, of course, depends on the number that you already have. It gets up too--it starts women have no children, very few, most of them want children, and they have one child that's enough for two. At two children already you have like 40% of women already saying, two children's enough for me; again this is Morocco in the Mediterranean zone. Then when you get up to six children almost everybody says enough. The average for the whole country is--that's like 53.3%. More than half of the women say, okay no more children, and again this data is seven years old, it's even lower now.
You compare this to Mali and this is the number of women that don't want any more children, and I think the final there is 8.6 or something, an enormous difference. That no matter how many children they have even--this is eight--six and more children, still only a very few, about a third of them say six or however many I have, six and over is enough for me. This is in respect of those two, you might say, well Niger is a very poor country, Morocco is not anywhere near so poor, it has something to do with infant mortality. This is indeed Morocco, and look infant mortality has come down quite a bit. It's getting there and so you say, oh well that's why Morocco--Moroccan's want and have fewer children because they have a better situation with infant mortality, but then you look at Niger and not--it's not as good as Morocco but it's still come down quite a bit and since then it's come down further.
You expect--well you'd see some response in the fertility levels to that but you don't, you don't see it at all. What's the difference? It's not religion. So both Niger and Morocco are Sunni Muslim, and as far as I'm aware, there's no big differences in the interpretation of religion there. You see the same story in Christian Sub-Saharan Africa countries. This is Tanzania, again about the same years, and basically no change in fertility--a little drop in very recent times.
Zambia is coming up next, in Zambia it's--even went higher and then it's down back to where approximately where it started. This is characteristic. It's not a religious thing. There's something special about Sub-Saharan Africa. Even South America doesn't look like this at all. If you're in South America the fertility is way, way down. There is something quite special about Africa, and we're going to have to try to figure out what that is.
You'll read a really interesting article by John Caldwell which talks about a whole culture of reproduction. Again, Africa is a huge place, has many different cultures and we're just talking Sub-Saharan Africa. North Africa is a different story; South Africa we have the European settlement, that's another different story, but the bulk of Central Africa to some degree fits this. You have places where you don't have bad soil, so in the tropics Java has volcanoes, volcanoes replenish soil. The mountain slopes of Kenya have good soil from--again from volcanic soil. The stories there are a little different. In general, we're talking about those parts in Africa where it's hard to stay alive, it's hard to get a population going that we're--that places traditionally under populated and just now with Western medicine are the population rates coming up to where you might consider it crowded. A place like Nigeria now is certainly crowded.
In Africa, reproduction is at the core of--the central core of traditional culture. Their religious ideas are all tied in, very--essentially, with reproduction in the lineage itself that means your line of ancestors. The prime duty of a human, in this cultural setting, is to reproduce the lineage, keep the lineage going. This is not at all unique to Africa. In Indonesia I saw there was an awful lot of this going on and I'll talk about other examples of it. It's very pronounced in Africa but not in any sense unique.
The idea is that--one of the ideas is that when a man dies he doesn't just disappear. We have a nice funeral service and say bye-bye, and maybe once a year we come and give flowers onto the grave, but we have no sense that that person is still around. In these traditional parts of the world the person lives on in kind of shadow world, but he can communicate with his descendants. That's often not very difficult, and he's dependent on his descendants for sustenance. If they don't feed him and give him what he needs in the afterlife he is in big trouble. If a man does not have descendants then he really doesn't get anything when he dies.
Again, I saw this in Bali enormously, where there was enormous effort to bring offerings to the recently dead ancestors. They're very, very sensible about it. You see in Bali the women carrying these--they're beautiful in their beautiful dress, and they have these huge platters on their heads filled with the most delicious fruits and arranged just gorgeously, and they bring them to the temple and the ancestors can partake of them, and the next day they come and take it home and eat it, because they understand that the ancestors are getting spiritual not the physical stuff. So they leave it there and then the ancestors can take what they get out of it, and then the humans can take what they get out of it, so it's not wasteful. Every store and every house will have a little--every day a little thing out in the front with a little bit of grain and everything. The dogs come by and eat it. Of course the dogs come by and eat it, but that's okay. The ancestors have taken, and the spirits have taken what they want out of this.
In temperate zones we associate religion and our culture--big empires, big states, the United States is huge and any western country population is large compared to say a Balinese Village or an African Village. Religion is big. How many billions of Christians are there, how many billions of Muslims are there, of Buddhists and Hindus, we got everything--everything is big.
In Africa, in a sense, each family's ancestors are its gods, and both traditional and political authority, and religion are very, very local affairs. They're not agglomerated into big things. No one expects the people in this village to worship the same as the people in the next village. There isn't so much the idea of a central monotheistic type of god which is--that comes up when you have empires. You have a central emperor and you have a central god. When you don't--when your political thing is just your village, again traditional times, there's no concept, no need to have these either central political leaders versus central religious gods. Immortality for you is provided by your descendants.
Immortality is very local; it's your own descendants. That changes in Western religion, especially in the Muslin Judeo-Christian tradition. It's the religion, it's God that gives you immortality. It's not your descendants, so everybody's interested in immortality; it's very important whether you go to heaven or hell and so forth. The huge shift is whether it's given to you by your descendants, whether they take care of you and give you a kind of immortality, or its given to you by your big mega-religion, which tells you what you have to do in order to gain immortality.
When a person dies, there again, they don't go off to a distant heaven, they stay right locally and gradually after a few generations they kind of disappear into the mist and they have a very careful departure. Again, in Indonesia, again comparing tropical regions, one of the big islands is called Sulawesi or Celebes as we say in Western languages. Again, in many different cultures, but in some of them a person dies, you don't want to disturb that person because they can do bad stuff to you.
You swaddle them; he's going to rot, so you got problems, you give him swaddling clothes and you sit him in a chair, him or her, in a chair right in his own bedroom, right where they live in houses sort of, thatch houses, and they sit there for a long time and gradually as they decay, they smell, they take off the swaddling clothes, get rid of that and swaddle them up again until they're down to bones. And then they're taking up--so they're not disturbed, by that time they're ready, they don't have their flesh anymore, they're ready to leave, so they take them to these big cliffs overlooking the village, and there's caves, natural caves in the cliff, and the dead bodies are brought up there to sit, and look down over the village, they're not very far away. It's really quite wonderful.
I was in Bali stumbling around under funny circumstances in a cemetery, and all these graves were open. I said, what's going on are they expecting--have they dug an awful lot of graves expecting everybody to die soon? No, it turns out that a rich man had just died. Now the poor people want to provide for their ancestors in the next life but they don't have money; they don't have any stuff, so they bury him and they wait until a rich man dies. Then a rich man has this huge procession. They're wonderful things to see with big caskets, and big chariots, and all this--just wonderful preparation and he's very rich and the rich man's body is thrown into the ocean and all kinds of stuff is thrown into the ocean to support this rich man in his afterlife.
Well, the poor people, and it's quite okay because it's a very communal culture Bali, very supportive of poor people, they dig up their bodies, and they bring them in the same time the rich man is put into the ocean. Poor people are put into the ocean. They partake of all of this. What happens the next day, of course the ocean--all the coins and what not have come up on the beach and the rag-pickers, the really poor people come by and collect all this stuff. It has--this cultural act of burying the rich, not only does it equalize the afterlife of the rich people and the poor people, but the very poorest people who are still alive get some income out of it as well as of course everybody who prepares the funeral. It's a wonderful sort of way that everything sort of hangs together as they usually do in cultures. We will continue next time.
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