From about 1800 to about 1825, Thomas Malthus published several papers on a single important point: in times of relative ease, population increases geometrically. This means if you have 100 people in this generation, you'll have perhaps 150 in the next, 225 in the next, 337 in the next, 506 in the next, and so on. However, the ability to grow food raises only linearly: if you can feed 100 people in this generation, then perhaps 150 in the next, 200 in the next, then 250, then 300, then 350 and so on. The inevitable result: poverty then malnourishment then starvation in the lower classes. Of course the upper classes always do just fine.
In the 200 years since Malthus, many people have predicted starvation for the whole world based on his ideas. Up until about 20 years ago, science was able to improve agriculture at such a rate and wars and pogroms killed so many people that it didn't happen; perhaps many thought it never would. It's happening now, and it's going to get worse. A lot worse. Below is a chart of world population from 1950 to 2050, based on UN figures and projections. World population, about 2.5 billion in 1950, about 6.7 billion today, is projected to raise to over 9 billion by 2050. We can easily see that the bulk of this growth will be in Asia and Africa; the population in Europe and the Americas is projected relatively unchanging.
Why does population grow? The simple answer, "too many kids," is only partially correct. Populations grow for four primary reasons:
These effects are caught in a particular graph called the "population pyramid." You graph the number of people in a region at various ages. If there are few adults and lots of children, then you see that the women are each having lots of kids and the kids will grow up and have lots more. If there are many adults and few children, that population is in decline. Some simplified population pyramids are shown below:
Much of sub-sarahan Africa looks like the first graph: lots of children, few adults. The high birth rate, relatively low infant mortality, and adults dying of AIDs and malaria make for a very unstable situation. Arabia looks like the second graph, Arabian women are having about six children each on average and those countries can afford the medical care to keep their adults relatively healthy. The US and Europe look like the third graph, we have relatively long life expectancies and only enough children to replace people as they die. Japan looks like the fourth graph, the Japanese are dying out due to a great disinterest in having children or allowing immigration.
Let's look at the world in terms of each of these four affects. First, life expectancy. Where are people living longer? Answer: In the entire world, save for Africa after 1985. In Africa a lack of farm land, clean water and basic health care is lining up with wars, AIDs and malaria to lower the average life expectancy.
Next, infant mortality. In what parts of the world do lots of infants die of disease or malnourishment? Broadly speaking, there's a rich world, North America, Europe and Australia where nearly all infants live. There's a third world, South America and Asia, where infant mortality is noticeably higher. And there's Africa, where lots of infants die.
Next, the number of children the average woman has in her lifetime. Again, we see broad conclusions: childbirth is below the replacement rates in Europe, Canada, Australia, China; it's roughly at the replacement rates in the US, South America, India; and it's completely out of control in Africa.
Last, the proportion of the population that is young and likely to have children in the next 20 years. We substitute a chart of median age for this. Once again, North America, Europe and Australia have older populations with fully half the people past the typical age of having children. Asia and South America have younger populations that speak of a trend not yet played out. And Africa is a disaster in the making.
There are some well known correlations with these trends. The largest is with per capita GDP. It's not enough to know how much money is in a country, you have to divide up the money among the inhabitants. Bill Gates has $40 billion, his children will never want for anything imaginable. If Nigeria had that same $40 billion to divide up among their 150 million population, that's about $300 per person - that money would not last long at all. Per capita GDP is the Gross Domestic Product, everything the population makes, divided by the population, so basically it's the average income per person. In the charts below we see that when per capita GDP drops below $5,000, the average income drops below $5,000, then infant mortality shoots up and life expectancy drops off dramatically.
And how does Africa look in these terms? African population is increasing geometrically, and their GDPs in many area are actually dropping due to wars and disease. The UN projection for African population and per capita GDP show that the population, blue line, is steadily raising, and the per capita GDP has just recently dropped below our magic number $5000 and will continue to drop to below $1000 in the next 30 years. It's popular in this country to hear "Someone should do something!" In this case, the "something" would appear to involve a transfer of wealth from North America and Europe, the wealthy countries that breed responsibly, to Africa of around $5 trillion per year. North America and Europe have about 800 million people, so that's a transfer tax of about $6,000 per person per year. Call me cold hearted, but I'm not interested in sending over $24,000 per year (I have three children). I would be willing to send over $100 or so per year in the form of inexpensive birth control. Bill Gates hopes to save Africa with his $40 billion, but we see he's most likely going to run many trillions of dollars short. In fact, his efforts to contain AIDs and malaria will most likely result in an increase in the breeding population and a worse problem in 20 years.
In 1950, North America, South America and Africa had about 200 million people each. Europe had about 500 million. Since then Europe's population has been roughly flat, and the Americas are showing slow growth, tending towards leveling out. Africa, meanwhile, will grow in 100 years from 200 million to 2 billion people. The projection is for a huge Malthusian catastrophe in Africa, as the death rate increases to match and surpass the birth rate. Meanwhile, we can expect that the African environment will be all but completely destroyed - the time to go on Safari is now, it won't last much longer.
The Indian subcontinent also shows strong growth, where again the catastrophe has already started - it's estimated that 1/3 of Indians live with Amoebic Dysentery, and 75% have no access to drinkable water - their major rivers are all basically huge sewage dumps, punctuated with floating bodies. India's major rivers have coliform (fecal) bacterial counts up to 3,000 times higher World Health Organization safe standards, yet this is their water source for drinking, bathing, cooking, washing, and irrigation.
One can easily say that the African and Indian populations must be brought to a stable, sustainable level, but this will happen not due to economic forces and education like in Europe or the Americas, nor due to political forces like in China: it will happen due to starvation and huge epidemics, of an unimaginable scale that the rest of the world will be helpless to mitigate. A couple billion infants and children are going to die in the next 40 years of starvation and disease because Indians and Africans can't get clear on the idea that if they can't feed themselves, they certainly can't feed six kids.