One of the most remarkable facts about the past century is that the population of the poor countries went from about one billion to about five billion. We are used to taking for granted that poor countries have a population explosion. The "population bomb" fears have not really been that NATO was getting too big too fast, but that the world was going to be overrun with poor people.
We sometimes forget what an amazingly positive sign this is about the world. There is enough wealth in the modern world that even poor countries can support huge numbers of children, with gigantic increases in their numbers. Sure, many people in those countries are malnourished. In some places they even starve to death, though that is more the result of some government trying to kill them than it is from an absolute shortage of food. The gigantic increase in population in the 20th century, which is without precedent in the history of the world, is a great testimony to the new wealth that modernity has created.
Most of the increase came from better sanitation and medicine for kids. The next step is to get control of how many kids we have, given the new reality that most will survive. This happened in the first world long ago. It is happening in the poor nations now. Livi-Bacci, in The Concise History of World Population, says the single most important variable in regulating births is, not surprisingly, what percentage of women use birth control. In rich countries, about 70% of women in childbearing years use birth control. In Latin America the rate is 57%, in Asia as a whole about 50% do (with huge variations by country). Africa is the continent that has reduced its birth rate the least; not surprisingly, only about 23% of African women practice birth control.
At the beginning of the modern era, and even into the 20th century, the North Atlantic countries were population leaders as well as economic and political powers. In the 21st century, Asia and Africa will be the population leaders, and their economic power will rise. Their political power will probably rise, especially for certain countries. This power and growth is, in part, the fruit of the world miracle of massive population growth.
Big populations do create problems. But people are good things, and lots of them are mostly the source of good things for the world.