The Quiet Galaxy

Explanations · They were never there

Rare life: getting from chemistry to the first living cell may be so unlikely that it almost never happens

Proposed by Jacques Monod, 1970 fl smaller

Nobody knows how life started on Earth. It happened at least once, fairly early, but no one has made it happen in a laboratory, and no one can say how probable it was. If the step from ordinary chemistry to a self-copying cell is extremely unlikely, then most planets that could carry life never do, however comfortable they are. On this view the galaxy is full of warm, wet, lifeless worlds, and Earth is the one in many billions where the dice came up right. The silence is the sound of a lot of empty oceans.

The idea is old and has no single owner. The French biologist Jacques Monod gave it a famous form in 1970, writing that the universe was not pregnant with life and that our number came up in a game of chance. Francis Crick, who shared the Nobel prize for the structure of DNA, wrote in 1981 that the origin of life looked almost like a miracle, given how many conditions had to be met, and went so far as to suggest life had been sent to Earth deliberately. Few scientists went that far, but the underlying worry has never gone away: we have one example of life starting, and one example tells you nothing about the odds.

The argument from the one example cuts in both directions, and that is the heart of the matter. Life on Earth appeared early, within a few hundred million years of the planet becoming habitable, which has long been read as a sign that it starts easily. But a planet where life started late might never have produced anyone to notice, because the Sun's slow brightening is expected to end Earth's oxygen-rich air in about a billion years and complex life took most of the available time to appear. So the early start may say more about us than about life: we could only exist on a planet where life began promptly, whether or not that is typical. Two careful statistical treatments of this point differ in what they find. The one published in 2012 (David Spiegel and Edwin Turner) found the early start inconclusive: it fits an arbitrarily low chance of life starting, and a second, independent origin would tell us far more. The one published in 2020 (David Kipping) found that it mildly favours life starting quickly rather than slowly, at odds of a little better than three to one, and Kipping himself describes that as a gentle nudge.

In the Drake Equation this is the factor for the share of suitable planets on which life actually starts. Every other factor can be large; if this one is tiny, the product is tiny. It is also the factor about which the least is known. Estimates in the literature run from nearly one, on the view that life is a natural consequence of chemistry given time, to numbers so small that life would be expected only once in the whole observable universe.

The objections are mostly about ignorance rather than evidence. The chemistry of life's beginnings is better understood every decade: the building blocks of proteins and of the genetic code form readily in conditions found on the young Earth and in space, and laboratories have shown several plausible routes toward self-copying molecules, though not yet the whole path. The discovery that the same building blocks fall from the sky in meteorites suggests the raw material is everywhere. Defenders of the rare-life view reply that raw material is not the problem; the problem is the enormous number of steps between raw material and a cell, and nothing yet shows that any of them is easy. The question will be settled by evidence, not argument: a second origin of life, in the oceans of an icy moon in our own solar system or in the atmosphere of a planet around another star, would end the debate overnight.

What it says about the equation

Every explanation is a claim about one or more of the seven pieces that are multiplied to give the number of detectable civilisations. This one bears on 1 piece:

The test: what would strengthen or weaken it

Would strengthen it: Decades more of origin-of-life chemistry without a demonstrated path from simple molecules to a self-copying system; a survey of many planets in the band around their stars where water stays liquid finding no gases that life produces; the oceans of Europa or Enceladus turning out to be sterile despite having water, warmth and the right chemistry.

Would weaken it: A second, independent origin of life found anywhere, whether in the solar system or in the atmosphere of a planet around another star; a laboratory demonstration that self-copying chemistry arises readily under conditions common on young planets; evidence that life on Earth started more than once.

These two lines are what the record is read against when a new paper or discovery is logged. A result of the kind named here, published with its evidence, is what would settle it; a press claim on its own settles nothing.

The last reading

Once a week the records are read against the news, each against the test above. Open a line to see what that week held. Every reading ever made of this record is on the reading page.

  • 2026-10-16 Logged, no change By hand

    No second origin of life anywhere, and no evidence that life on Earth started more than once. Toward weakening: a 45-letter RNA molecule that copies itself and its complement (Gianni and others, Science, 2026-02-13), far smaller than the copying machines studied for thirty years, which the authors read as such molecules being commoner in sequence space than assumed; the Mars potential biosignature (Hurowitz and others, 2025-09-10) and Enceladus's ocean organics (Khawaja and others, 2025-10-01) are ingredients and conditions, not life. The Europa and Enceladus oceans have not been shown sterile. Logged.

    Gianni, 2026Hurowitz, 2025Khawaja, 2025 source 1source 2source 3

How seriously it is taken

A respectable minority position among origin-of-life researchers and a common view among physicists who write about the Fermi question; most biologists lean toward life being at least moderately common but admit the evidence is thin.

The papers that bear on it

Books, films and other work that take it up

Read next

Notes

Checked 2026-10-16. Monod's English translation (Chance and Necessity, Knopf, 1971, page 180, as cited at https://en.wikiquote.org/wiki/Jacques_Monod) reads "The universe was not pregnant with life nor the biosphere with man. Our number came up in the Monte Carlo game." Crick's Life Itself (Simon and Schuster, 1981) is quoted as saying that the origin of life "appears at the moment to be almost a miracle" (quoted from the book at https://pic.hallikainen.org/piclist/2004/b/12/11/053909a.txt and summarised at https://www.sciencefriday.com/articles/origin-of-life-is-earth-exceptional-book/); no page number was found and the book itself was not reached. Corrected 2026-10-16, two points. (1) The body said both statistical treatments found the early start mildly favours life being common. Spiegel and Turner (Proceedings of the National Academy of Sciences 109, 395-400, 2012; https://arxiv.org/abs/1107.3835) found the early start inconclusive and consistent with an arbitrarily low chance of life starting; only Kipping (same journal, 117, 11995-12003, 2020; https://doi.org/10.1073/pnas.1921655117) found a mild preference, with betting odds above three to one that life starts quickly, and also odds of three to two that intelligence is rare. (2) The body said the Sun will make Earth uninhabitable in about a billion years. The sources give different figures for different things: Ozaki and Reinhard (Nature Geoscience 14, 138-142, 2021, https://doi.org/10.1038/s41561-021-00693-5) put the end of Earth's oxygen-rich air at 1.08 billion years, give or take 0.14; Wolf and Toon (Geophysical Research Letters 41, 2014, summarised at https://astrobiology.nasa.gov/news/under-the-bright-lights-of-an-aging-sun/) find Earth could keep its oceans for at least another 1.5 billion years. The body now says the oxygen-rich air.

Think this page gets the explanation wrong, or misses an objection? Say so, or read how disagreement gets folded in. The record itself is data/explanations/rare-life.toml in the public repository. This page's address will never change; if the explanation is ever retired, the address will say what replaced it.