Children of Men: Premises and Poetry

Some viewers have questioned "Children of Men's" underlying premise. That's reasonable; the film asks us to accept a world, twenty-odd years in the future, in which no human babies have been born for two decades, and doesn't bother to give a scientific explanation why to its characters or its audience.
The fact that other mammals have clearly been reproducing just fine over the period in question really bugs some viewers, while some fans are already devoting hours of geeky fun to figuring out a good reason for the discrepency. Both responses are as natural as can be, and surely result from a risk director Alfonso Cuaron and the film's many writers knew they were taking.
But trying to rationalize the barren plague at the aching core of "Children of Men" perhaps blinds the film's detractors and lovers alike to a potent, poetic metaphor. Cuaron and his crew have, as many have noted, created a future world that really looks very much like today's. Fear of foreigners, idealism degenerated into terrorism, all manner of social, moral and spiritual erosion, rising authoritarianism, near-perpetual warfare - these diseases are loose upon the Earth now, and most seem to be gaining strength.
If things continue along such lines, the film says without ever actually saying it, mankind has no future. So, the babies stopped coming.
It's not a scientific explanation, I know, but "Children of Men" depicts a nightmare - a visceral one that often feels as real as the last firefight in Baghdad, but a fantasy nonetheless. And like most dreams, and most great movies, it is fraught with symbolism.
So get hung up on the how of the missing children if you must. But the question of why that this thoughtful, searching and heartrending film poses is the truly, troublingly profound one.