It is a nearly unmentionable scandal of civilized life, or, more generally agricultural life, that it produces more people than the world has room for. It's no secret, of course, since the Rev Malthus prominently discussed it 217 years ago. That influential essay, which inspired Darwin and gave economics its grim nickname - The Dismal Science - hasn't exactly been forgotten, but its hardly mentioned in modern economics. It's fashionable to pretend that progress and capitalism "refuted" Malthus.
The truth is that something like the opposite has occurred. Modern technology has permitted birth control, and where it has been aggressively pursued, economic progress has nearly always followed. China is the poster boy. The vast decline in the World's extreme poverty that we have seen in the last thirty years is mostly due to the rapid economic progress of China, and that progress followed the one child policy.
What I really want to talk about, though, is the means that agricultural and civilized societies have used to get rid of the spare humanity. Of course natural processes, like disease, do some of the work, but my impression is that essentially every such society has developed institutions to do the dirty work. A few such deserve mention: slavery, war, class systems, mass punishments, ostracism, and human sacrifice.
We live in one of the richest societies of history, and a moderately generous one, but we still have our disposable people - the homeless, our enormous criminal class, drug addicts, prostitutes and all those that live on the crumbs that fall from society's table. Our huge prison population is probably the clearest example. Many or most of those in prison are no more dangerous to society than the average tobacco salesman or fake charity scam artist, but we do dispose of them at great expense. Of course their are psychopaths and other genuinely dangerous or destructive people who need to be kept off the streets, but they are far from a large majority.
We know the means to control the sort of population increase that requires this kind of human destruction. Simple education of women is by far the most effective step. Where that doesn't work, mildly coercive measures like taxes on excess children might help.
UPDATE: I think that the commentators may be missing the point. One of the founders of economics, probably Malthus, noted that in his era in Britain, the odds of a poor Irish child surviving to adulthood were some huge factor worse than those for a prosperous English child - in effect only the children of the rich were contributing to future population. That strikes me as a hellish way to run a civilization, and one that is no longer necessary.
In fact, only vestiges of this "disposable people" practice exist today, at least in the most civilized countries.