Shadows of Things That May Be

The Season

December is the month of the shortest days: the light shortens until the solstice and then, slowly, turns. It is also the month of counting down, to year's end and to Christmas, and the season of Dickens's ghosts of past, present and yet to come. People in pre-industrial societies sleep close to an hour longer in winter, so December also suits a theme about rest and pace rather than more effort.

The Biology

Every chromosome ends in a telomere, a run of repeated DNA that protects the chromosome end the way a knot protects the end of a thread. Each time most cells divide, a little of that end is lost, because the copying machinery cannot reach the very tip. When telomeres become critically short, the cell stops dividing or dies. This is one reason normal human cells can divide only a limited number of times, the "Hayflick limit". Telomere length is set largely at birth and inherited. Smoking, heavy drinking, chronic stress, poor sleep and inactivity are associated with faster shortening. Longer is not always better, though: telomeres that stay too long are linked to some cancers.

Anchor facts

• In cultured human fibroblasts, the length of telomeric DNA falls steadily with each round of serial division (Harley, Futcher & Greider 1990). Source ↗
• In a six-month randomised trial of 124 previously inactive adults, endurance and interval training raised telomerase activity and telomere length, but resistance training did not (Werner et al. 2019). Source ↗
• A Mendelian randomisation study found that genetically longer telomeres raise the risk of several cancers while lowering the risk of some non-cancer diseases (Telomeres MR Collaboration 2017). Source ↗

The Canon

• Plato — Republic, Book X, Myth of Er (c. 375 BCE) — 616c–617d, the Spindle of Necessity. The three Fates sit around the spindle, "Lachesis singing of the past, Clotho of the present, Atropos of the future" (Jowett trans.). Spinning, measuring and cutting line up with telomerase, attrition and senescence.
• Hesiod — Theogony (c. 700 BCE) — lines ~217–222 and ~904–906. The Moirai appear twice, first as daughters of Night and then of Zeus and Themis, and they allot good and ill at birth. This is the inherited, largely fixed starting length of the thread.
• Shakespeare — Sonnet 60 (1609) — lines 1–2. "Like as the waves make towards the pebbled shore, / So do our minutes hasten to their end". Each wave works as a cell division: a finite count, each one taking a little from the shore.
• Andrew Marvell — "To His Coy Mistress" (1681) — lines 21–22. "But at my back I always hear / Time's wingèd chariot hurrying near". This is the felt pressure of the count. The essay can turn it: telomeres count divisions, not hours, and the pace can be eased.
• Charles Dickens — A Christmas Carol (1843) — Stave Four, the Ghost of Christmas Yet to Come. Scrooge asks: "Are these the shadows of the things that Will be, or are they shadows of things that May be, only?" This is rate, not fate: the past length is given, the present sets the pace, and the future stays open.
• Alfred, Lord Tennyson — "Tithonus" (1860) — line 1 and the poem's premise. "The woods decay, the woods decay and fall". Tithonus received endless life without endless youth. The thread that will not end is its own curse, as in long-telomere cancer syndromes.