According to a recent paper by a math professor at the University of Arkansas, the existence of life on Earth provides proof that abiogenesis is relatively easy on planets similar to Earth, refuting the “Carter argument” conclusion.
Does the presence of life on Earth provide any insight into the likelihood that abiogenesis—the process by which life first emerges from inorganic substances—occurs elsewhere? That is a question that has baffled scientists for a while, as well as everyone else inclined to think about it.
Astrophysicist Brandon Carter makes the widely accepted claim that the selection effect of our own existence limits our ability to observe. Nothing can be concluded about the likelihood of life existing elsewhere based on the fact that we had to end up on a planet where abiogenesis took place.
He claimed that understanding life on this earth had, at best, neutral value. Another way to look at it is to say that because Earth wasn’t chosen at random from the group of all Earth-like planets, it can’t be seen as a typical Earth-like planet.
However, a recent paper by retired astrophysicist and University of Arkansas mathematics instructor Daniel Whitmire argues that Carter’s logic was flawed. Whitmire contends that Carter’s theory suffers from “The Old Evidence Problem” in Bayesian Confirmation Theory, which is used to update a theory or hypothesis in light of new evidence, despite the fact that it has gained widespread acceptance.
After giving a few examples of how this formula is employed to calculate probabilities and what role old evidence plays, Whitmire turns to what he calls the conception analogy.
As he explains, “One could argue, like Carter, that I exist regardless of whether my conception was hard or easy, and so nothing can be inferred about whether my conception was hard or easy from my existence alone.”
In this analogy, “hard” means contraception was used. “Easy” means no contraception was used. In each case, Whitmire assigns values to these propositions.
Whitmire continues, “However, my existence is old evidence and must be treated as such. When this is done the conclusion is that it is much more probable that my conception was easy. In the abiogenesis case of interest, it’s the same thing. The existence of life on Earth is old evidence and just like in the conception analogy the probability that abiogenesis is easy is much more probable.”
In other words, the evidence of life on Earth is not of neutral value in making the case for life on similar planets. As such, our life suggests that life is more likely to emerge on other Earth-like planets — maybe even on the recent “super-Earth” type planet, LP 890-9b, discovered 100 light years away.
Reference: “Abiogenesis: the Carter argument reconsidered” by Daniel P. Whitmire, 23 September 2022, International Journal of Astrobiology.