Is aging inevitable?

A new study has appeared to support an old idea: Aging is inevitable and immutable, so anti-aging research is doomed in advance to failure.

In 1957, George Williams wrote

This conclusion banishes the “fountain of youth” to the limbo of scientific impossibilities where other human aspirations, like the perpetual motion machine and Laplace’s “superman” have already been placed by other theoretical considerations. Such conclusions are always disappointing, but they have the desirable consequence of channeling research in directions that are likely to be fruitful.

In 2002, three prominent aging scientists wrote (in Scientific American):

No Truth to the Fountain of Youth:
…no purported anti-aging intervention has been proved to modify aging…We find it ironic that a phony anti-aging industry is proliferating today…Some [researchers] Some assert that aging’s complexity will forever militate against the development of anti-aging therapies.

One of the three was Len Hayflick, who is most famous for having discovered and documented one of the clearest and most preventable mechanisms of programmed aging.

In 2017, Joanna Masel wrote

“Aging is mathematically inevitable. Like, seriously inevitable. There’s logically, theoretically, mathematically no way out.”

This new study is based on statistical analysis of human and primate populations. Among the 42 authors (!) who signed it, I am chagrined to find the name of J. W. Vaupel. Et tu, James? Over several decades, Vaupel has been the optimist of demography, telling us that somewhere in the world, human lifespan is always continuing to increase, as it has done since 1840, at the rate of about 1 year of new lifespan for every 4 years that passes. For the first 130 years of this advance, the improvement in lifespan was predominantly about preventing infant mortality and combatting infectious disease. But since about 1970, lifespan improvements have continued to benefit the elderly. My informal index is the number of 80-year-olds I see on the tennis courts. Vaupel and his former student, Annette Baudisch, also were prime movers in a comprehensive 2013 study of Aging Across the Tree of Life, which catalogued species that don’t age at all for decades at a time, and others that become demographically younger.

This new computer model—like all computer models—is a translation into mathematical language of a set of assumptions about a natural phenomenon. The crank turns, and out pops a prediction. The sleight-of-hand, the conjuror’s trick, is that we are tempted to look at the mathematical machinery to see where these predictions come from. But equally important is to look at the assumptions on which the mathematics is built.

Snail Survivors

In this case, the assumption is that natural selection has been trying to maximize lifespan, because the longer an individual lives, the more opportunity it has to reproduce. And reproductive output is the measure of success in neo-Darwinian logic.

But if we look at the biology of aging, it’s clear that evolution has not been trying to maximize lifespan. As we get old, genes are turned on that destroy us with inflammation and autoimmunity, and this epigenetic change shows every sign of being under the body’s control. As we get old, genes are turned off that rebuild and protect the body against chemical damage, most famously from free radicals. Again, it appears that this is deliberate. It is a product of natural selection, not a constraint on natural selection.

How can this be? How can a variety with lower reproductive success prevail in evolutionary competition against other varieties with higher reproductive success? This question has been the primary focus of my own research for 25 years, and my answer is the necessity to preserve stability of ecosystems.

My answer may be right or wrong—it is still a minority opinion. But what is clear is that the lifespan of almost all living things is under epigenetic control. That is, aging is a programmed phenomenon. Aging is not the accumulation of damage. Aging is not the body wearing out. Rather, aging derives from processes of self-destruction that are under the body’s control.

In this perspective, aging looks a good deal less inevitable than this article claims. And indeed, there is cutting-edge science that appears to be turning back the clock of aging, turning old rats into young rats.

Specifically, what does the new study find? Looking at populations of humans and other primates, they find that longer average lifespans are associated with less variability in lifespan. In other words, the short-lived primates have deaths that are spread out, with some living much longer lives; but in the longer-lived primates, age-at-death is clustered up near the high end. This gives the appearance of some kind of wall at the high end of lifespan.

And where, specifically, is the flaw in the new paper?

“Understanding the nature and extent of biological constraints on the rate of ageing and other aspects of age-specific mortality patterns is critica…”

The implicit assumption about “biological constraints” is that the constraint is physical, or that in some way it is beyond the reach of evolution. The assumption is that natural selection has pushed against these constraints, and hit a brick wall. The alternative view (a view that is shared by some of the most prominent researchers who have studied physiology and biochemistry of aging) is that these “constraints” are actually baked in by natural selection itself. Far from being constraints on evolution, these constraints are actually the product of evolution. This is to say that the constraints are not fundamental physical limits, but features built into the epigenetic cycle of growth, development, and aging. The “constraints” become malleable as we tinker with the signaling mechanism by which the body imposes aging on itself.

A crucial caveat

I believe that as we understand more about epigenetics and the signaling mechanisms that control biological age, it will become increasingly feasible to manipulate lifespan. Indeed, we’re already doing this to a huge extent in lab worms and, to a good extent, in rodents.

But evolution isn’t so dumb. Limits on lifespan have been put in place to help protect against population overshoot. And (my opinion) humans are already in a state

of severe population overshoot, in the context of sustainable limits of Earth’s biosphere. I believe that whether or not biological science succeeds in further extending lifespan, it is an urgent matter for survival of our species (and many other species) that we shrink the human footprint on the biosphere and on the soil, water, and atmosphere that support Earth’s ecology. I think that living well with less is a relatively simple technical problem. We need only implement all currently known efficiency improvements in the use of resources, and continue to discover new ones. But it is a huge political problem that we have barely begun to confront, and I don’t have any good ideas how to make these changes a political reality. I’m going to stick to the science, and count on others who are more adept at politics than myself. As we extend human lifespan, there is an urgent need to move toward sustainable agriculture and to adopt energy-efficient technologies.