Our health, standard of living, and REAL progress (not the meaning of the word that has been hijacked by socialists, degenerates, and perverts) is not tied to population density (we are nowhere near this bottleneck, which is less optimistic than the author suggests, but not by much) - it is mostly tied to advancing technology and free markets.
Our available resources are not fixed, but are a function of technology. And the rate of technological advancement is a function of the number of people involved in research. The major flaw in fatalistic calculations underpinning the "overpopulation" debate is that technology is assumed fixed. At best, there are a few studies that attempt to correct for this flaw by assuming technological progression at the present rate - but even this is still flawed. The pace of progress continually hastens, and as much as the thought hurts to some some people, we can thank population growth, not just worldwide improved access to and quality of education.
We NEED more people, not fewer. We can grow at a high rate, for at least another few thousand years, while enhancing our standard of living, as long as there is access to education, and unhindered research; most difficult of all, however, is to garner another critical ingredient - less failure-rewarding, success-punishing socialism in all forms. The elimination of competitive forces in markets, in research, in laws, and through entitlements, via arbitrary compulsory redistribution, generally acts to cause long-term harm. Another major lesson from the last several hundred years is that central planning is ruinous - the more expansive the scope, the more disastrous the results.
Anyway, personally, I hope to raise as many children as the author. :)
You have a great analysis of the scientific side of this discussion. I had not thought about all of them previously. Thank you for your input.