Into Something Rich and Strange

The Season

January is named for Janus, the two-faced god of doorways, who looks back at the damage the year has written and forward to what can still be prevented. It is also the northern winter, when UV is at its lowest and sun habits can be planned calmly, and it is US National Radon Action Month, the heating-season moment when public-health bodies ask households to test the air they breathe.

The Biology

Every cell carries a copy of the same text, about three billion letters long, and every day that text is damaged thousands of times by ordinary metabolism, by sunlight, by smoke and by chance. Dedicated repair crews fix almost all of it. What they miss becomes a permanent change, copied into every descendant of that cell. Over decades our tissues become mosaics: patches of cells carrying different small edits, a few of them growing faster than their neighbours. This slow drift is genomic instability, the first hallmark on the López-Otín list. It is one of the roots of cancer and a contributor to how tissues age. We cannot undo mutations already made, but we can reduce the damage coming in and protect the conditions under which repair works.

Anchor facts

• By middle age, sun-exposed skin from normal eyelids already carries thousands of mutations per cell, with many mutant clones under positive selection (Martincorena et al., Science 2015). Source ↗
• Across 16 mammal species, somatic mutation rates scale inversely with lifespan, so a mouse and a human end life with a broadly similar mutation burden (Cagan et al., Nature 2022). Source ↗
• In people who have quit smoking, a population of near-normal cells expands to make up a much larger share of the airway lining than in current smokers (Yoshida et al., Nature 2020). Source ↗

The Canon

• Ovid — Fasti (c. 8 CE) — Book I, lines 65–66 and Janus's speech that follows. "Iane biceps, anni tacite labentis origo, / solus de superis qui tua terga vides." The two-faced god sees his own back: an image for the January audit, reading the accumulated record of exposure while facing the year's prevention.
• Ovid — Metamorphoses (8 CE) — Book I, lines 1–2. "In nova fert animus mutatas dicere formas / corpora." The poem opens with "changed forms", the root of our word mutation. Ovid's bodies change under pressure from outside forces, much as tissues are reshaped by UV, smoke and time.
• Geoffrey Chaucer — "Chaucers Wordes unto Adam, His Owne Scriveyn" (c. 1385) — lines 5–6. "So ofte adaye I mot thy werk renewe, / It to correcte and eek to rubbe and scrape." The poet complains that he must keep correcting his careless copyist. It is the clearest literary picture of DNA repair: an author scraping errors off the vellum before they are copied onward. In manuscript transmission, one scribe's slip passed into every copy made from his exemplar.
• William Shakespeare — The Tempest (c. 1611) — Act 1, Scene 2, Ariel's song "Full fathom five". "But doth suffer a sea-change / Into something rich and strange." Bones become coral, eyes become pearls. The song lets the essay hold a harder truth: an aging body is not simply degraded but transformed into a mosaic of altered cell lines, some harmless and some dangerous.
• Mary Shelley — Frankenstein (1818) — Volume I, Chapter 4 (Chapter 5 in the 1831 edition), the night of the creature's awakening. "I had selected his features as beautiful. Beautiful!—Great God!" Victor assembles good parts and gets a flawed whole. Clonal expansion works the same way: each mutant clone is a local success, and together they can build something that no longer answers to the body's plan.
• Jorge Luis Borges — "The Library of Babel" (1941) — Borges imagines a library holding every possible book, including every misprint of every true one. That is the space of possible mutations: nearly all of them nonsense, a few meaningful, and the reader lost among them.