Is the origin of life a fluke? Four researchers weigh the odds

Nobody knows whether life's origin was a fluke. The four researchers here cannot say, because the evidence is one planet. What they offer is four different ways of asking the question, and none of them presents a calculated probability for life starting.

Dmitry Korkin, a professor of bioinformatics and computational biology, treats it as a probability. Asked about the chance that life emerges on a habitable planet, he guesses lower than one percent, and warns that this is intuition and that he is not the best person to estimate it. He thinks Earth was lucky, since conditions when life emerged were not ideal, but he does not think Earth is unique. He notes a report of a simple amino acid found in comet dust.

Adam Frank, an astrophysicist, attacks the best-known argument that life's key steps were improbable. That argument reads the late arrival of intelligence on Earth as a sign of a few very unlikely steps. Frank answers that planet and life change together, so the timing needs no improbable steps, and that a step which seems to have happened once may only reflect lost records or a niche already filled. He does not say the origin is easy: "We have n equals one example of life. So that means we could be an accident". His bound is that humanity is the only technological civilization ever only if the odds per habitable-zone planet are below one in 10 to the 22.

Sara Walker, an astrobiologist and theoretical physicist, stops asking about odds. She describes the origin as an abrupt physical transition, when molecules that catalyze each other close a loop and reinforce their own existence. She thinks it could be reproduced and measured in a laboratory, and predicts first contact with alien life will come in an origin-of-life experiment.

Nathalie Cabrol, of the SETI Institute, prefers to ask what life is. She says our thinking about the origin is biased because we are the only model we know. The ingredients are abundant everywhere, and from theories of life as a result of thermodynamics she concludes that "if we are alone, then the universe is a statistical absurdity".

They disagree on whether a probability is even the right tool. Walker and Cabrol also split on entropy: Cabrol leans on it, and Walker calls that approach wrong because it does not explain how order arises from randomness. Korkin's and Frank's numbers do not actually collide, since one concerns life starting and the other a civilization ever arising. Some reported findings mentioned are dated or disputed, so check where they stand now.

What to do with it: when you see a probability for life arising, ask what it is a probability of. Treat a single percentage as intuition unless a method is shown. Do not take a single occurrence as proof that a step was improbable. Read the Drake equation as a list of what we do not know. Watch origin-of-life chemistry as closely as telescopes. For a claimed biosignature, ask how complex the molecule is to build and whether it exists in many copies. A confirmed second example would change everything.