No human has ever lived forever, and nothing available today can make that happen. The oldest verified person, Jeanne Calment, died in 1997 at 122 years old, and no one has come close since. But the question isn’t as far-fetched as it once was. Over the past two decades, scientists have identified specific biological mechanisms that drive aging, and several experimental therapies are now in clinical trials aimed at slowing, pausing, or even partially reversing those processes. Living forever remains firmly in the realm of science fiction. Living significantly longer and healthier, though, is an active area of serious research.
Why Your Body Ages in the First Place
Aging isn’t a single process. It’s the accumulation of several types of cellular damage happening simultaneously. Two of the most important are telomere shortening and cellular senescence.
Every time a cell divides, the protective caps on the ends of your chromosomes (called telomeres) get a little shorter. Once they shrink past a critical length, the cell receives a permanent stop signal and enters a state called senescence. It stops dividing but doesn’t die. Instead, it lingers in your tissues, releasing inflammatory molecules that damage neighboring cells. Over time, these “zombie cells” pile up in your organs, contributing to everything from joint stiffness to cardiovascular disease to cognitive decline. The DNA damage at shortened telomeres is essentially irreparable, which is why the body treats it as a permanent alarm.
On top of that, a growth-promoting pathway called mTOR, which is essential during development and healing, stays active as you age in ways that become harmful. Rather than helping you grow, it drives cells to become overactive and dysfunctional. Many age-related diseases, from certain cancers to metabolic syndrome, are partly a consequence of this continued cellular “hyperfunction” long after it’s needed.
Drugs That Target Aging Itself
The most studied longevity drug is rapamycin, which works by dialing down the mTOR pathway. Originally used to prevent organ transplant rejection, it has extended lifespan in nearly every organism tested. Researchers investigating its use for longevity in humans have settled on a weekly dose of 5 to 7 milligrams, far lower and less frequent than what transplant patients receive. Even 1 milligram daily has shown no side effects in healthy elderly people in early studies. The drug is remarkably non-toxic at these levels. One case report noted that a person who took 103 milligrams in a single dose during a suicide attempt experienced nothing worse than temporarily elevated blood lipids.
Rapamycin doesn’t stop aging. It appears to slow the progression of age-related diseases by calming overactive growth signaling. Whether that translates into meaningfully longer human lifespans is still unknown, but multiple clinical trials are underway.
A second approach targets those zombie cells directly. Senolytic drugs are designed to selectively kill senescent cells while leaving healthy cells alone. The most studied combination pairs dasatinib (an FDA-approved leukemia drug) with quercetin, a compound found naturally in onions and apples. In animal studies, this combination reduced markers of cellular aging in fat tissue and reversed age-related inflammation. Several human clinical trials are now testing whether clearing senescent cells can improve conditions like osteoarthritis, kidney disease, and frailty in older adults. The idea is simple: remove the cells that are poisoning their neighbors, and tissue function improves.
Boosting Your Cells’ Energy Supply
A molecule called NAD+ is required for hundreds of essential reactions inside your cells, including DNA repair and the activity of sirtuins, a family of seven proteins that regulate gene expression and aging. NAD+ levels decline substantially with age, and that decline is linked to mitochondrial dysfunction, insulin resistance, and neurodegeneration.
Supplements like NMN and NR are precursors that your body converts into NAD+. In animal studies, NMN supplementation has improved insulin sensitivity, reduced age-related fat tissue inflammation, enhanced brain function, and restored mitochondrial performance. Human research is still catching up. David Sinclair, a prominent aging researcher at Harvard who takes NMN himself, has reported that his blood biomarkers at nearly 60 resemble those of someone closer to 31. That’s a single anecdote, not proof, but it reflects the enthusiasm driving dozens of ongoing human trials.
Measuring Biological Age
One of the breakthroughs enabling this research is the ability to measure how old your body actually is, as opposed to how many birthdays you’ve had. Epigenetic clocks analyze chemical tags on your DNA (specifically, methyl groups attached to certain sites) that change in predictable patterns as you age. The original clocks, developed by Steve Horvath and Gregory Hannum, predicted chronological age with surprising accuracy. Newer versions like DNAm PhenoAge, which reads 513 specific DNA sites, go further by predicting your risk of disease and death independent of your calendar age.
This matters because it gives researchers a way to test whether an intervention is actually making someone biologically younger, not just healthier-looking. If a drug can measurably reverse your epigenetic age, that’s far more compelling than simply reporting that someone “feels more energetic.” These clocks are already being used as endpoints in longevity clinical trials.
What Nature Has Already Solved
Biological immortality does exist in nature, just not in anything resembling a human. The hydrozoan Turritopsis dohrnii, often called the “immortal jellyfish,” can revert from its adult form back to a juvenile polyp when damaged or stressed. It does this through a process called transdifferentiation, where mature, specialized cells reprogram themselves into entirely different cell types.
Genetic analysis of this process reveals that during the reversal, the jellyfish activates genes involved in DNA repair, lifespan regulation, control of cell division, and the suppression of transposable elements (bits of DNA that can move around and cause damage). It also ramps up genes associated with embryonic development and tissue remodeling. In essence, the jellyfish hits a biological reset button, activating repair and regeneration pathways while suppressing the cellular chaos that normally accompanies aging. No one is close to replicating this in humans, but the molecular details are helping researchers understand which repair pathways matter most.
The Practical Ceiling for Now
Even optimistic longevity researchers don’t claim immortality is on the horizon. The realistic goals of current science are to extend the healthy portion of human life, compressing the years of disability and disease into a shorter window at the very end, and possibly pushing maximum lifespan beyond its current apparent limit of around 120 years.
The tools for doing this are more concrete than they’ve ever been: drugs that calm overactive growth pathways, compounds that clear damaged cells, supplements that restore declining cellular energy, and epigenetic clocks that can measure whether any of it is working. What’s missing is long-term human data. Most of these interventions have strong animal evidence and early-phase human trials, but proving that something extends human lifespan takes decades by definition.
For now, the interventions with the most evidence behind them remain unglamorous: caloric moderation, regular exercise, adequate sleep, and not smoking. These consistently show up as the strongest predictors of both lifespan and healthspan across large population studies. The pharmacological approaches may eventually surpass them, but they haven’t yet.