New theory concludes life’s likely origin on Earth-like planets

Does the existence of life on Earth tell us anything about the likelihood of abiogenesis – the origin of life from inorganic substances – arising elsewhere? That’s a question that has puzzled scientists and anyone else who thinks about it for some time.

A widely accepted argument by Australian-born astrophysicist Brandon Carter argues that the selective effect of our own existence limits our observation. Since we had to be on a planet where abiogenesis was occurring, nothing can be inferred from this knowledge alone as to the likelihood of life elsewhere.

Knowledge of life on earth, he argued, is of neutral value at best. Another view is that Earth cannot be considered a typical Earth-like planet because it was not randomly chosen from the set of all Earth-like planets.

However, a new paper by Daniel Whitmire, a retired astrophysicist who currently teaches mathematics at the U of A, argues that Carter used flawed logic. Although Carter’s theory is widely accepted, Whitmire argues that she suffers from what is known as the “old evidence problem” in Bayesian confirmation theory, which is used to update a theory or hypothesis in the face of new evidence.

After Whitmire has given some examples of how this formula is used to calculate probabilities and the role played by ancient evidence, Whitmire turns to what he calls the conceptual analogy.

He explains: “One could argue, like Carter, that I exist regardless of whether my conception was easy or difficult, and therefore nothing can be inferred from my existence alone as to whether my conception was easy or difficult.”

In this analogy, “hard” means contraception. “Simple” means that no contraceptive was used. In each case, Whitmire assigns values ​​to these statements.

Whitmire continues: “However, my existence is ancient evidence and must be treated as such. When this is done, the conclusion is that it is much more likely that my conception was easy. In the case of abiogenesis of interest, it’s the same. The existence of life on Earth is ancient evidence and just as in the conception analogy, the probability that abiogenesis is simple is much more likely.”

In other words, the evidence for life on Earth is not of neutral value in arguing for life on similar planets. Therefore, our life indicates that life is more likely to arise on other Earth-like planets – perhaps even on the recently discovered “super-Earth” planet LP 890-9b, discovered 100 light-years away.

Math enthusiasts can read Whitmire’s essay “Abiogensis: The Carter Argument Reconsidered” in the International Journal of Astrobiology.