What separates someone managing a pharmacy's worth of medications at seventy-five from someone who's just getting started on the road to a hundred and two? In this episode, we crack open the biological instruction manual of the world's centenarians and read its most remarkable pages. We start with a crucial distinction — the difference between lifespan (how long you live) and healthspan (how long you live well) — and the striking pattern researchers call the compression of morbidity: the way the very longest-lived people tend to stay healthy far longer and then decline quickly, burning clean and steady rather than guttering out over decades.

From there, we tour the genes that show up again and again in centenarian studies across the globe. We meet APOE, the double-edged gene whose different versions tilt the odds toward risk or pro ...