Medicine keeps getting better, so why does almost nobody make it past 120? No one has ever been verified past 122: Jeanne Calment, who died in 1997. 👇
• In 1961, Leonard Hayflick found that normal human cells divide about 50 times and then stop. They don’t die. They retire, a state called senescence.
• Freeze the cells after 20 divisions, thaw them out, and they do about 30 more. Something inside keeps count.
• The counter: telomeres, the caps at the tips of your chromosomes, like the plastic tips on a shoelace. They’re a six-letter DNA code (TTAGGG) repeated over a thousand times. Every copy leaves the very end uncopied, so the cap gets shorter, and long before it wears through, the cell stops dividing.
• Telomerase can rebuild the caps. On its own, that isn’t cancer, but nearly 9 in 10 tumors switch it on. Shrinking caps are one of your body’s brakes on cancer.
• The disposable soma theory (Thomas Kirkwood, 1977): evolution spends limited energy on growing up and having kids, and gives your body just enough repair to get through your reproductive years.
• For most of our 300,000 years, life expectancy at birth was around 30, mostly because so many children died. Adults who made it often reached their 60s or 70s. Today the world average is about 73, and over 80 in rich countries.
Aging isn’t a punishment. It’s a trade-off.
Sources:
• Hayflick and Moorhead, Experimental Cell Research (1961) · Hayflick, Exp Cell Res (1965)
• Kim et al., Science (1994): telomerase in 90 of 101 tumors · Bodnar et al., Science (1998)
• Kirkwood, Evolution of ageing, Nature (1977)
• Gurven and Kaplan, Population and Development Review (2007)
• UN World Population Prospects 2024 · Gerontology Research Group (Jeanne Calment)
Images:
• Jeanne Calment, 1895 (public domain)
• Leonard Hayflick, 1972: AP photo (public domain)
• Telomere caps micrograph: U.S. Department of Energy Human Genome Program (public domain)
• Tom Kirkwood photo: Bengt Oberger, CC BY-SA 4.0, via Wikimedia Commons
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I’m Zhuzi from TzFilm — short, clear explainers on the tech and science behind everyday things.
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