You know the ones, as soon as you say that the world is overpopulated they jump in and say "There is not a shortage of food, we produce enough food but it is not getting to the people who need it."
Wait, who said anything about food? There are hundreds of other issues related to human overpopulation concerns and I would not even say food is in the top ten.
In experiments done in the 1950's and 1960's John B. Calhoun proved that food was not an issue. He did experiments on rats and mice, providing them with an ideal environment, one in which food was never denied. The populations grew and then collapsed.
In his experiments, Calhoun observed that as populations grew at first the subjects became more violent, had increased sexual behavior (including more sexual aggression), and some became anti-social. He noticed mother animals became less nurturing and even started to show aggression to their own young, sometimes killing them. Eventually the mother animals stopped mothering their young altogether, and the males stopped showing interest in the females, the animals behaved more like zombies than rats or mice.
|Universe 25 photo source|
Anyone who is interested can read up on "Behavioral Sink" which is the term Calhoun gave to his observations.
The point being that food is not necessarily an issue with human overpopulation, and that when we reach a point of being overpopulated there are other concerns - such as increases in anti-social behavior and violence (wait, haven't we reached that point?). So, to anyone who is ignorant enough to still think that just because we have enough food we can continue to pump out babies, I suggest you open your eyes!
The 2006 movie "Children of Men" explores a future in which humans have also reached a point where they are no longer able to produce young. This movie was based on the book "The Children of Men" by P.D. James who most certainly must have been familiar with Calhoun's studies.