India, April 6 -- Picture the scene. A longevity enthusiast takes an ice-cold water dip at 5 am, having already taken 15 supplements and uploaded his morning bloodwork to an app. Across the world, a scientist stares at a petri dish of cells that, according to her data, have just been made biologically younger. Both people are obsessed with the same question. But they are operating in entirely different realities.

It would seem that we are in the middle of a longevity gold rush. The global anti-ageing market is projected to surpass $120 billion within the decade, fuelled by a cultural obsession with eternal youth, bio-hacked bodies, and the vague promise that death might one day become optional. Yet if you talk to scientists who have devo...