The real problem with overpopulation seems to have to do with the fact that the human information dissemination and processing system (the "Cybersphere") is unable to deal with long-range planning. A single human brain is larger than a walnut, but that makes no difference. The system reacts to new information but doesn't really process it. And we are no better suited than dinosaurs to survive the challenges ahead.
Those of us who remember the 1970s and the 1980s may still have in mind how, in those years, speaking of overpopulation and birth control was not considered politically incorrect. Julian Simon (the "doomslayer") gives us a good description of the debate of those years (he was, needless to say, strongly against the idea that overpopulation was a problem).
Yet once again there is hysteria about there being too many people, and too many babies being born. Television presents notables ranging from Andrei Sakharov to Dan Rather repeating that more people on earth mean poorer lives now and worse prospects for the future. The newspapers chime in. A typical editorial in the June 3, 1989 Washington Post (p. A14) says that "in the developing world...fertility rates impede advances in economic growth, health, and educational opportunities". Nobel- winner Leon Lederman says in his statement as candidate for the president of the American Association for the Advancement of Science that "overpopulation' is one of our "present crises" (2 June, 1989 Announcement, p. 2). The president of NOW warns that continued population growth would be a "catastrophe" (Nat Hentoff in The Washington Post, July 29, 1989, p. A17). The head of the Worcester Foundation for Experimental Biology calls for more funding for contraceptive research becasue of "Overpopulation, together with continuing deterioration of the environment..." (The Wall Street Journal, August 14, 1989, p. A9). And this is just a tiny sample of one summer.Simon's analysis is in good agreement with the results of a Google Ngram search. The term "overpopulation" reached a popularity peak in the 1970s, then it started a decline that's still ongoing.
You can see the same behavior with concepts such as "birth control" and also using "google trends." So, what happened that made the very concept of overpopulation obsolete? Surely, population growth continue and it is still continuing (image from Gerald Marten):
So, why did people lose interest in overpopulation just while it kept becoming a bigger problem? Something similar took place with other concepts such as the limits to growth and peak oil: people are losing interest just now that these problems are becoming gigantic and probably unsolvable.
I can propose a tentative explanation based on the recent work we have been performing with my coworkers, Sara Falsini and Ilaria Perissi. We have been examining the behavior of memes on the web using a simple viral propagation model, the same commonly used in epidemiology. It is called the SIR (susceptible, infected, recovered) model. Here it is in a simple form (image on the right).
The model can be modified to take into account re-infection, which causes the interest in the meme not to go to zero after the peak. Theoretically, this parameter could be affected by events occurring outside the cybersphere, but we found that, apparently, people rapidly become resistant to re-infection for most memes.
Eventually, we have a problem that has to do with the capability of the cybersphere to process information. The cybersphere is not a "brain." When subjected external forcings in the form of memes, it reacts by readjusting some of its parameters, but no more than that. It can't act on external problems by long-term planning; it doesn't have the tools for that. We may call it a "governance" problem or, perhaps, a "command and control" problem. In any case, the system is nearly completely blind to external threats. We see this most clearly for the question of climate change. And that makes it likely that we'll go the way the dinosaurs went.