I know some of you prefer the punch line right up front, so for that camp, here you go: A population of some 7 billion Homo sapiens simply cannot eat much meat. Period.
In my world, the debate about meat-eating often devolves to competing views about nutrients, advanced with that penchant for dogma and religious fervor that have come to figure so prominently and detrimentally in all things nutrition. There are cases to make for and against saturated fat, for and against dietary cholesterol, for and against dairy, and for and against protein intake at any given threshold.
From only slightly greater altitude, the debate is about dietary patterns, but rooted in much the same considerations. There are vegetarians to one side, Paleo diet enthusiasts to the other.
I think the most ardent of vegans, and the most carnivorous proponents of the Paleolithic diet have nearly comparable cause to love and hate me. In both cases, I have defended the merits and strived to expose the flaws in the exaggerated arguments that abound. I suspect the vegans may find a little more to love and less to hate, since I land, in the company of Michael Pollan, with the confident recommendation to eat "mostly plants."
In fact, a true Stone Age diet could well be the healthiest diet for our species. Despite the hype to suggest otherwise, we certainly don't have the evidence to prove that, but importantly, we have no evidence to disprove it either. There are no long-term, randomized trials pitting an optimal Paleo diet against a comparably optimal Asian, Mediterranean, vegetarian or vegan approach.
But a relative absence of evidence was not the only consideration to bedevil that prior paragraph. I advisedly used the terms "true" and "optimal." A true and optimal Stone Age diet would be comprised of foods extant in the Stone Age, and consumed by our Paleolithic forebears. That would mean some wide variety of wild plant foods and wild animals -- most if not all of which are now extinct. Unless you have recently seen, and eaten, a Mammoth, you are obligated to concede that a genuine "Paleo" diet is not possible. Much then depends on the fidelity with which the concept of our native diet is recapitulated.
Generally, the rubric is invoked to justify more meat, fewer plants. So in the cacophonous static of modern-day nutrition, a penchant for Paleo means bacon and grain-fed beef, often with an allowance made for cheese; whether or not it means arduous daily physical activity, a wide variety of plants, a daily fiber intake approaching 100 grams, and so on -- all of which were thought to figure in our native experience. Paleo at its core has virtues, but it has become a convenient banner to fly over a plate of pastrami.
Which brings us back to future. We cannot eat much meat any more, no matter the nutritional merits or demerits. The debate over nutrients is so myopic as to be downright silly. The debate over competing diets is seen with only slightly greater clarity from very slightly greater height.
If we draw back and view the argument with the dispassion of some genuine altitude, a much bigger truth is as plain to see as a dust bowl.
We have all seen just this kind of truth from altitude, manifested as an epic battle between two ants. Now, of course, at their scale, ants are a lot stronger than we are. But who cares about their scale? On our scale, they are ants. And while the red ant and the black ant are locked in a colossal, life-and-death, winner-take-all battle, we are invited to reflect ruefully that we could settle the matter with a single tap of the toe. The epic argument of ants devolves to pointlessness beneath the shadow of a boot.
And so we come to it. For we are the ants, our endless "my diet can beat your diet" battles the pointless conflict, and the planet wears the boots.
Imagine if there were 7 billion lions on the Earth. Unlike us, lions -- in common with all great cats -- are indeed constitutional carnivores. For them, it's meat, or greet your maker.
Adult lions consume on average between 10 and 25 pounds of meat per day. That translates to between 3,650 and 9,125 pounds of meat in a typical year. The best estimates suggest that something close to 2,000 gallons of water are required to produce one pound of beef. That figure is perhaps lower for the wild game free-ranging lions eat, but perhaps not much.
If we go with the 2,000 gallons/pound of flesh estimate, then every adult lion would chew through between 7,300,000 and 18,250,000 gallons of water annually, not taking into account what they drank. If we use the high-end estimate and apply it to all 7 billion lions, that would be 1.3 X10 to the 16 power, or 13 quadrillion gallons. That's four times the volume of Lake Superior, which contains roughly 10 percent of the earth's fresh water.
Of course, there aren't 7 billion lions on earth -- there are only 30,000 or so. That's because while lions may be kings of beasts, Homo sapiens call the shots at the top of the food chain. There are more than 7 billion of us -- and that's the primary reason there are dramatically fewer lions than there were just decades ago. We are taking ever more of the world's acreage, food and water for ourselves.
And while even the most devotedly carnivorous of us could never match the meaty appetites of lions, we could certainly chew through an awful lot of meat. That much more so if our meat-eating proclivity persists as our population swells to the predicted 9 billion of us, or 12 billion.
Folks, it comes down to a pretty basic choice. We can either have a whole lot fewer of us meat-eating Homo sapiens, or we need Homo sapiens to eat a whole lot less meat. The funny thing is, the rate-limiting issue makes the plant vs. animal nutrition debate irrelevant. It's all about water.
As noted a couple of days ago in the New York Times, a switch from a standard omnivorous to a vegetarian diet would reduce an individual's water consumption by roughly 60 percent. A reduction in animal foods and commensurate increase in plant food alternatives such as beans and legumes could produce half that benefit.
We derive and defend our competing arguments about diet -- with preposterous, unfounded conviction -- as if we can eat whatever we want. But whether the argument is as old as the Stone Age, or as new as the latest incarnation of fad-diet hooey, it is comparably subsumed within the larger truths and greater forces that govern the planet. Bickering over what nutrients do or don't do ignores other salient considerations, from land use to the treatment of other species. But in the end, even all of that is just so much dust in the wind. For on a dry, dustbowl planet, there are no good choices left -- and everybody's just too damn thirsty to take any interest in the hot new dietary claim.
Unlike lions, we Homo sapiens are not constitutional carnivores. On the other hand, we have very clearly been eating meat since before our genus spawned our species. There is nothing intrinsically unethical or unhealthy in meat-eating. I believe my vegan friends should concede this.
But there are more than 7 billion of us now, not the isolated roaming bands surrounded by pristine expanses that characterized the Stone Age. With the great power to shape the fate of the planet comes the great responsibility to think beyond the boundary of our dinner plates. Our diet debates circumscribe much more than our meal choices. They potentially circumscribe the Serengeti, and the world's aquifers.
Even the king of beasts is subordinate to the laws of nature. We, my Homo sapien cousins, are as well.
So we find ourselves back at that punch line. We may debate our meat-eating proclivities as if mightier than lions. But we are also, in the grand scheme of larger forces, feebler than ants -- however inclined we may be to forget it from our arrogant perch atop the food chain. The reminder, though, will get increasingly unpleasant. All our passions and rants will ultimately prove to be moot -- for we are ants in the shadow of the planet's great, dusty boot.
Author, Disease Proof
Follow David Katz, M.D. on Twitter: www.twitter.com/DrDavidKatz