Reversing human aging: it’s time to consider the consequences

• Aging

Science may soon be able to slow, stop, or even reverse the aging process in humans. What will happen when people can live on and on for centuries?

Within the next two decades we will extend the healthy human life-span indefinitely and, in doing so, alter human culture forever.

Our maximum life-spans will not have become infinite, but indefinite: uncertain and unknown. The social consequences of extended life-spans are also unknown but likely to be explosive. The increase of healthy life-spans to perhaps double or more our current spans will trigger social changes greater perhaps than any since those that followed the invention of agriculture more than 10,000 years ago.

The changes will largely be positive, particularly the prevention of individual suffering from the diseases and fears associated with aging. But the changes will also be disruptive and detrimental to our culture and to our personal lives. Societal change, even when the outcome is favorable, always presents challenges. Peace on earth would put soldiers out of work; curing heart disease would require retraining for cardiologists. No matter the innovation – agriculture, sailing ships, the printing press, gunpowder, industrialization, the automobile, atomic energy – each one caused (and in some cases is still causing) disruption in the social order.

The degree to which any innovation alters society hinges not on how remarkable, expensive, or unexpected such innovation is, but rather on the degree to which it changes basic forces and assumptions in our lives and our society. Never before have we altered our basic assumption about maximum human life-span. The mean human life-span has changed radically within merely the last two centuries, from 25 years in the eighteenth century to 50 years in 1900, to 75 years now. This pattern reflects access to food, clean water, and basic medical care (such as immunizations and obstetrical care), and therefore defines much of what we mean by a “developed nation.” The fact that some developed nations (such as Japan and Sweden) have longer mean life-spans and less infant mortality than others (such as the United States) is often used as a telling criticism of the degree of social development, as though civilization itself were in some measure defined by health and life-span.

Throughout the course of history, however, we have never increased the maximum human life-span, estimated at 120 years. Some have extrapolated this historical precedent to its logical end, arguing that we will soon have mean life-spans of 100 or more, yet still age rapidly and die by 120. This extrapolation assumes that the maximum life-span cannot change – a reasonable assumption historically. No matter what the medical advance, we have never yet altered the maximum human life-span one year, let alone a decade. The mean life-span alters on a whim: a fastened seatbelt, a smoke detector, a clean well, or a tetanus shot. The maximum life-span has been beyond us, unalterable, fixed, and reliable.

Until now.

Already, scientists have extended the maximum life-span in two species: to twice normal in the fruit fly (Drosophila) and six times normal in the nematode worm (C. elegans). Extending the human life-span appears almost within reach.

Stopping and Reversing the Clock

We know that our cells age and die; recent discoveries suggest that they don’t have to. Cells have chromosomal clocks – called telomeres – that determine their life-spans, and they age and die as their clocks run down. But cancer cells, for example, continually reset their clocks, allowing themselves to divide – and live – forever.

The telomere shortens as a cell divides because the cell fails to copy the tip of its chromosomes, where the telomere resides. Telomere “caps” are being built by researchers at the University of Texas that would essentially force the cell to always copy its telomere – and hence never shorten. The clock would never wind down, and the cell (and the person possessing it) would cease aging.

But we could also try for more than stopping the clock – we could reverse it. By adding telomerase – an enzyme, part protein and part RNA – we could relengthen the telomeres. “All” we would need to do is lengthen all 92 telomeres in each of our 100 trillion cells. It may be possible one day to produce a drug that gets each of our cells to treat its own 92 telomeres. Active research programs for telomerase inducer drugs are being conducted by the University of Texas’s Southwestern University Medical Center and by Cold Spring Harbor Laboratory on Long Island, New York, as well as by biotech and pharmaceutical firms.

We have no way of knowing what the maximum healthy life-span will become when we reextend human telomeres. We suspect that by using telomerase inducers we can probably extend the human life-span well beyond 120 years and that telomere manipulation should allow us to prevent most of the diseases we associate with aging: cancer (albeit by the reverse process of inhibiting telomerase), atherosclerosis (and so most heart disease and strokes), osteoarthritis, Alzheimer’s, and most other diseases of aging.

Social Consequences

One social consequence of preventing aging will be a likely increase in the world population. A large world population is not inherently a bad thing. If the world population were only 1,000 people, would we have computers, immunizations, or even books? But at some level, high population does have liabilities that lower the quality of life. The optimal number of people depends on your assumptions about a number of variables, such as environmental damage, food supply and production, crime, war, disease, and overwhelming social “stresses” and their impact on the human condition.