“We don’t know” — said by someone who would know
Vadim Gladyshev runs a laboratory at Harvard studying the comparative biology of aging. The work spans model organisms — mostly mice — and the species that break the rules: whales, naked mole rats, bats. It also spans human cohorts, tissues and cells. The comparisons are the point.
One of them is quietly startling. The cells inside your body share a genome and an ancestral cell, yet have wildly different lifespans: some turn over constantly, while neurons and cardiomyocytes are expected to last the whole life. Same instructions, same organism, radically different longevity. Whatever explains that is likely to explain a great deal else.
His definition of aging is the accumulation of the negative changes that come from being alive — molecular damage, mutations, byproducts of metabolism, other forms of disorganisation. But he refuses to be glib about what follows from it. What is the enemy? What should an intervention target? Damage? A programme? Function? He points out that function is treacherous as a measure: cognitive performance swings across a single day by something like a decade’s worth, and you can train muscle and cognition upward. Does that mean you became younger? He does not think the question has been answered.
Then there is the comparison that should unsettle the whole field. Nature has changed mammalian lifespan enormously — from an ancestral animal of roughly twelve years, some species went down, others went far up — and it did so apparently easily. In the laboratory we fail. Caloric restriction, rapamycin, lifestyle: ten, twenty, occasionally forty percent in mice, and in humans perhaps two or three. Whatever nature is doing, he concludes, is not what we are doing.
And so the sentence that gives this page its title. He says it without drama, as a working scientist stating the state of the evidence: we do not currently understand aging — and anyone telling you otherwise, or claiming to know how to target it, is wrong.
