C Chen

In the aging orchestra of the body, every musician once played their part precisely. With age, some musicians do not leave the stage but stay and start playing out of tune, and so loudly that they drown out their neighbors. These cells, which have stopped dividing but have not died, release dozens of inflammatory molecules, and this noise accelerates the aging of healthy tissues.

At the end of every chromosome sits a cap made of repeating DNA letters: the telomere. For a long time it was measured as an average length across all chromosomes, as if judging a library by the average thickness of its books. But in humans, three ends, 17p, 20q, and 12p, are consistently shorter than the rest, and they are the ones more often linked to genome damage.

In a hall of mirrors, a person walks up to a curved mirror and sees themselves now as a dwarf, now as a giant. Popular machine learning models behave in much the same way when asked to guess biological age from blood tests or brain scans: they stretch age at the extremes, underestimating it in older people and overestimating it in younger ones.

A molecular timer that counts out the seconds a thought is held has turned up in the thalamus. Working memory is a mental notepad that keeps information for a few seconds while we read, do arithmetic, or plan. Its capacity is limited, and over time the trace fades. But what exactly sets that time limit long remained a mystery.