Epigenetic Clocks
Your DNA keeps a second age that ignores your birthday and tracks how hard you've actually lived.
Grounded in the research on epigenetic clock
The clock idea
An epigenetic clock is a biological-age estimator. Your cells stick chemical methyl tags onto specific spots on your DNA, and that pattern drifts in a steady, readable way as you age. Train an algorithm on thousands of samples and it learns which spots move with age. Feed it a new sample and it spits out a number, your biological age, built purely from methylation. No birthday required. The chemistry, not the calendar, is doing the talking.
Where it started
Steve Horvath, a UCLA geneticist, published the first true multi-tissue clock in a 2013 Genome Biology paper. He trained it across roughly 51 tissue and cell types and landed on 353 specific CpG sites whose methylation predicts age almost everywhere, blood, brain, liver, the lot. Correlation with real age hit about 0.96. That it worked in one tissue is unsurprising; that one model worked across the whole body was the shock that launched the field.