Nobel laureate Venki Ramakrishnan: no law of nature rules out substantially extending life, but true immortality remains impossible as long as accidents, disease and wars can kill us

Nobel laureate Venki Ramakrishnan: no law of nature rules out substantially extending life, but true immortality remains impossible as long as accidents, disease and wars can kill us

On September 15, Scientific American published an essay by Venki Ramakrishnan, a Nobel laureate in chemistry.

Mayflies live for a few days, while bowhead whales and Greenland sharks live for centuries. Ramakrishnan explains this variation in evolutionary terms. Natural selection does not favor longevity for its own sake: it favors traits that increase reproductive success. A mouse is more likely to die from predation or starvation than from old age, so reproducing quickly offers a greater advantage than maintaining its body. A whale's size protects it, making continued investment in bodily repair worthwhile. Genes that help early in life can become harmful with age. Aging emerges as a side effect of these trade-offs, and each species has a limit to its lifespan.

Average life expectancy has roughly doubled over 150 years, yet the longevity record still belongs to Jeanne Calment, who lived to 122, and no one since her has reached 120. In July, the authors of a calculation of the human lifespan limit reaffirmed their estimate of around 125 years. Biologist João Pedro de Magalhães noted that this estimate holds only in the absence of interventions in aging.

Aging was once understood as wear and tear, but cells repair their own damage, and that repair becomes less effective with age. Damaged or stressed cells sometimes enter a state called cellular senescence: they stop dividing and release inflammatory molecules. Early in life, this response helps wounds heal and protects against cancer. With age, however, senescent cells accumulate faster than the body can clear them. Removing them in mice can improve many features of aging, but indiscriminate removal carries risks.

Removing senescent cells aims to slow aging, while partial cellular reprogramming attempts to reverse it. In 2006, biologist Shinya Yamanaka showed that activating four genes returns an adult cell to an embryonic state. Resetting the age of cells might make it possible to reverse aging. Returning cells fully to an embryonic state is dangerous because they can form tumors. Researchers therefore activate the genes briefly, which appears to rejuvenate cells while preserving their tissue identity.

Ramakrishnan considers this method the most convincing route to rejuvenation: in mice, it has often improved tissue function and has reportedly repaired the optic nerve. It is now being tested in the human eye: on October 8, Life Biosciences, which uses three of the four Yamanaka genes, reported that three participants with glaucoma had tolerated the therapy well and that two had shown preliminary improvements on a visual field test.

Treatments for aging face a higher safety bar than drugs for fatal diseases: healthy people are unlikely to accept serious side effects from a drug they might need to take for decades. On substantially extending life, Ramakrishnan writes: “No scientific law rules out the idea, just as there is no reason interstellar travel should be impossible. The practical difficulties are simply enormous.” Aging involves many interacting processes, and a single intervention is unlikely to stop it without affecting other functions. The essay concludes:

“As long as accidents, natural disasters, disease and wars can kill us, true immortality remains impossible. And lives lasting hundreds of years are unlikely anytime soon. We can instead think of life as an endless banquet that people join and eventually leave. We should count ourselves lucky to be there at all and enjoy the feast while we can.”