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Your order, please?

October 10, 2024

What if we presented possible options for future human developments—let’s say human population as a solid example—and pretend it’s a menu from which we get to choose. What outcome would most people see as the desired goal? What would make them happy, or satisfied? Which population curve below do you think most would select?

I present the following options:

A: Indefinite exponential rise. This implies no biophysical limits, ultimately demanding expansion to space (as if possible).

B: Moderation into a linear rising state, allowing continued growth but not in crazy-pants fashion.

C: Logistic leveling: no drama: we found our place and aimed right for it with no corrections—like it was meant to be and we knew what we were doing all along.

D: Peak and modest decline to some medium and stable value, indicating a slight boo-boo (overshoot) in our trajectory.

E: Peak and substantial fall to a vastly smaller population before stabilizing. In this case, we had it dramatically wrong in a massive overshoot.

F: A post-peak crash to zero (i.e., extinction; could be due to ecological collapse, nuclear annihilation, sex robots, or classic evolutionary failure of our species).

Now picture yourself and a bunch of others sitting around a table at a restaurant holding this menu and trying to decide on the future. What are you having?

Process of Elimination?

Ha! I tricked you all! I would claim it’s not an open choice! It will be no surprise that I rule out option A. Exponentials fail, and juvenile space fantasies aren’t coming to the rescue. Even then, good luck maintaining an exponential against the cruel realities of expansive space! “I’m sorry sir, the kitchen informs me that this option is not available (and never has been).”

Option B also ignores biophysical limits, in that growth of any form is not a long-term realistic prospect, even if not disastrously exponential. Also unavailable from the kitchen.

I suspect many people in our society would pick option C. Looks tasty. This is the dream scenario: we figure out how to live on the planet and smoothly cruise into stability without any obvious sacrifice, then hold it there indefinitely as human civilization flourishes. Except: the scale of today’s activity on the planet far exceeds the community of life’s capacity to survive. Not only would the sixth mass extinction stay on track, but we have zero realistic all-things-considered plans for maintaining high-throughput modernity at the ten-billion person scale. From agriculture to energy to materials (upon which which energy conversion depends), we don’t know how this could possibly work for centuries or millennia. There’s no credible plan. Another note is that real populations seldom follow the no-drama logistic curve. Treat it as a fantasy, and try to ignore the appeal. You’re probably beginning to dislike this restaurant, for its lack of actual choice.

Option D is the first to acknowledge overshoot. I suspect the chef will get a smattering of orders from this category, just like the gluten-free, dairy-free “pizza” that’s on the menu for the rare bird who needs to go that way. This option admits defeat, of sorts. It acknowledges that we’ve gone too far already and need to dial things back in order to carry on. In spirit, I am on board. But if our current attack on the planet is at the level of rapidly initiating a sixth mass extinction, is a factor-of-two moderation nearly enough to tip the scales? “I’ll check with the kitchen—I’m uncertain whether this dish is available today.”

Option E is qualitatively similar to Option D, but quantitatively differs in that the ultimate steady-state level is vastly lower than the peak. This is not a small factor-of-two correction, but an order-of-magnitude or more. It’s the shoe leather option on the menu. Why would anyone ever pick this one? Well, if the other items are truly unavailable… This might be the only way to survive, by the dictates of evolution, ecology, and biophysics. The kitchen can probably oblige and rustle something up. Why is the chef now walking around bare-footed? Serving suggestion: goes down better with ketchup.

Option F is implicitly on the menu, folks. Dismayed by the lack of acceptable choices, we could refuse to order any of the unsavory options, insist on “living large,” and consequently end up starving ourselves in pointless protest.

Grade Analogy

I also like a grade parallel here. Students might desire an A or B, but can live with a C as a passing grade. D is effectively failure, and F is unambiguous failure. That leaves E: an obscure grade that is off our radar (outside Hogwarts). But we need to think out of the box here and accept that we are heading toward uncharted territory, for which we do not yet have set associations. If my choices are E or F, I might as well try this E-thing, which might turn out to exceed expectations.

Happiness?

This post was motivated by a discussion I had with a sharp friend about the path of humanity. I was making the point, unsurprisingly, that modernity is a temporary aberration that will not be ecologically supported for very long. He rejected the idea of any future path that had even a whiff of hunter-gatherer lifestyles, adding something to this effect:

Look: all you have to know to appreciate that human life was miserable in the distant past is that population was held down by external factors. Life was tough [nasty, brutish, short was the gist].

This is very illuminating. When I responded: “Ah, so the only mode of existence compatible with human happiness is unbounded, exponential growth?” it was immediately clear to him the pile he had just stepped in.

But this is the crux of the matter, and worthy of serious consideration. If the only way for humans to be happy (not miserable) is in a world without limits…well then we’ve come to the wrong shop, folks. If defiance of biophysical reality is necessary for us to be the transcendent, liberated former-animals we think ourselves to be, then I’ve got some bad news. Pinocchio will never be a real boy. Translation: our artificial construct of modernity will never have a permanent, integrated place within an ecological context.

Back to the Menu

Now let’s return to our menu. When presented in this way, I think logic circuits kick in so that most people—I hope—would recognize option A (indefinite exponential growth) as not being possible (otherwise it might seem the happiest choice). Once in this mindset, option B might also be apparent as untenable, and that’s certainly progress. If I am correct to suspect that option C would be most popular, aren’t we back to the “miserable” state of imposed limits?

I think the difference is that to most people, the target steady-state population is our choice—not nature’s choice—in which we have two kids on average, medically-enabled longevity, technological goodies, and opera. This is the “arrived” notion: under our control. What seems to be objectionable is when ecological realities are dictating the terms. Two things: first, ecological realities probably remove option C as being unsupportable to begin with; second, even option C is ultimately limited by biophysical reality, in that births are still constrained (restricted, independent of happiness/desire) and deaths still motor on. Population trajectories are all about biophysical realities of birth and death, so that any steady solution goes hand-in-hand with limits on the biophysical front. To maintain steady state, increasing longevity would have to be accompanied by a reduction in births. We can’t just do whatever we want.

I’ll make one other point with regard to my friend’s “misery” statement. It implies that every other species on the planet—constrained as they are by external factors beyond their control—must lead miserable lives, and that happiness rests on control. What a depressing mindset to hold about our glorious planet of life! I reject the notion that squirrels are miserable, or that early humans were miserable—and frightened—much of the time (see next week’s post). I take that attitude to be projection of our own unfamiliarity and fear over the prospect of losing the infantilizing influence of modernity. I have enough respect for early humans to believe that they faced challenges with grit and equanimity, while finding it within themselves to laugh, joke, tease, sing, and dance.

Overall Lesson

The point of this exercise is that not every drawing we could slap on paper is biophysically, ecologically supportable. In fact, the vast majority are not. It is probably approximately true that the area under the curve—above a certain threshold of sustainable population—is limited, as excess/overshoot leads to accumulating ecological damage, and an initially-healthy Earth can only take so much. This precludes, for instance, the pleasant notion of an arbitrarily gradual decline toward sustainable levels. Gotta keep the area below the breaking point. We can’t just do anything we wish. Does that lack of control commit us to misery? Careful: this is a tantrum-free zone.

Even in a deterministic mindset, where the ultimate answer is inevitable, the result is utterly unpredictable to us. Options E and F, for instance, both seem to be on the table, and I would rather that our species survives beyond the modernity episode than execute its extinction as a result of clinging to the colossal mistake of modernity for too long.

That means, if option F is to be avoided, steps must be taken to set us on the path of option E. Efforts in that direction come with no guarantees, but failure to make the attempt is far less likely to end up there.

Tom Murphy

Tom Murphy is a professor of physics at the University of California, San Diego. An amateur astronomer in high school, physics major at Georgia Tech, and PhD student in physics at Caltech, Murphy has spent decades reveling in the study of astrophysics. He currently leads a project to test General Relativity by bouncing laser pulses off of the reflectors left on the Moon by the Apollo astronauts, achieving one-millimeter range precision. Murphy’s keen interest in energy topics began with his teaching a course on energy and the environment for non-science majors at UCSD. Motivated by the unprecedented challenges we face, he has applied his instrumentation skills to exploring alternative energy and associated measurement schemes. Following his natural instincts to educate, Murphy is eager to get people thinking about the quantitatively convincing case that our pursuit of an ever-bigger scale of life faces gigantic challenges and carries significant risks.

Note from Tom: To learn more about my personal perspective and whether you should dismiss some of my views as alarmist, read my Chicken Little page.


Tags: future scenario, Population