Any gardener knows that to solve a weedy problem, you have to get it at its roots.

We in Preventive Medicine know that, too, or certainly should. Our eyes were opened to this enlightened thinking by McGinnis and Foege in 1993. They were the first to note explicitly that the causes of chronic disease and premature death are not diseases, but the things that cause the diseases! Such as tobacco use, eating badly and lack of physical activity.

The evidence that they were right has only accumulated ... and accumulated since. I routinely invoke this literature to note that feet, forks and fingers are the master levers of medical destiny, as regular visitors here well know.

Viewed differently, bad use of feet, forks and fingers are the major causes of chronic disease. But these are the proximal causes, not the root causes. The root cause is modern living. Everything about modern living that makes it modern -- processed food, suburban sprawl, labor-saving technology, mass media marketing -- is obesigenic, and conducive to the insalubrious application of feet and forks. More on that, however, can be a topic for another day.

For today, how about those eggs? Why is it that some 500,000,000 eggs have been recalled in the U.S. due to salmonella contamination? Proximal causes have much to do with modern farming and food handling techniques, and something to do with FDA resource limitations. But what about the root cause?

The root cause that connects these dots -- and many others besides -- is global population growth. There are too many of us.

This particular topic has something of a wince factor for me -- father of five! But former drug users often make the best addiction counselors and some of the top obesity experts struggle with their own weight. I suppose I can come clean about population pressures despite having done such a poor job of keeping my own genes to myself!

I raise the issue because it's ominously absent from almost all discussion of global warming and climate change, modern industrial agricultural practices, and the propagation and transmission of both infectious and chronic disease. This is odd, and worrisome. It suggests either obliviousness, fatalism or capitulation -- and none of these is good!

I was quite stunned when I spoke last year at the Imagine Solutions Conference in Naples, FL, that my fellow speakers addressing the trials and tribulations of the world spoke about a rapid ascent toward a global population of 9 billion or more as a fait accompli. Even though it was the driving force behind the problem they went on to discuss -- depleting of the oceans, climate change, deforestation, etc. -- it was not discussed as a problem in its own right. I had a similar impression when last I participated in the Aspen Ideas Festival.

If the harms of excessive global population have become a taboo topic, I didn't get the memo.

There are more than six billion of us here now. I am inclined to think there is no problem nine billion could solve that six-plus billion can't. However, nine billion may be the problem that the six-plus billion need to solve, if we are to solve any other. Because the growing horde of us consuming the resources of the planet in uniquely modern fashion is the problem underlying many other problems.

I could spell out how this root connects to the branches that populate our daily dose of bad news, but I suspect you can do that just as well yourself. For now, I am just saying we should all be thinking about it. And talking about it. And willing to say 'condom' in polite company -- and more importantly, in public policy.

The massive demands and ramifications of an ever-more-massive human population may be the root of the roots of many of our most urgent crises. It is something we can address by means at our disposal, but only if we are cognizant of it, and willing to talk about it.