A Scientist Just Mathematically Proved That Alien Life In the Universe Is Likely to Exist

Humans have spent centuries wondering if we are alone in the universe, or if there are alien beings somewhere in the vast reaches of space. Given that Earth remains the only planet that we know supports life—and we are not even sure how it arose here—it remains challenging to assess the odds that extraterrestrial life exists based on this lonely sample size of one.

These limitations in our knowledge prompted the theoretical physicist Brandon Carter to propose decades ago that the presence of life on Earth does not indicate that the mysterious process of abiogenesis, in which living organisms arise from inanimate matter, is more or less likely to occur on other planets. Now, a mathematician has revisited this idea and come to a very different conclusion with a more optimistic view about the existence of alien life.

During the 1970s, Carter developed an influential series of arguments based on this “selection effect” of our own existence. This view suggests that humans, as a species that lives on a planet where life emerged, cannot make objective inferences about the possibility that life may be present on other worlds, in part because we have no idea if Earth is typical of planets that might host life. For this reason, we cannot exclude the possibility that Earth may be the only world in the universe that supports living beings.

This argument is widely accepted in the scientific community. But now, Daniel Whitmire, an astrophysicist who teaches mathematics at the University of Arkansas, has presented a new challenge to Carter’s assumptions that suggests “the occurrence of abiogenesis on Earth-like planets is not rare,” according to a recent study published in the International Journal of Astrobiology.   

Whitmire told Motherboard over email that up until last year, he was one of countless researchers who thought that the Carter argument was “unassailable.” But he started to have doubts about its foundations during the peer review process for a different paper, when an anonymous reviewer offered an analogy between abiogenesis and human conception that inspired Whitmire to counter these long-held assumptions. 

In order to rethink Carter’s assertion that we can’t judge if abiogenesis on Earth was easy or hard, Whitmire draws a comparison to his own existence, noting that he is here regardless of whether his conception, or origin, was easy or hard. For the purposes of this thought experiment, conception would be “hard” if contraception was used, and “easy” if it was not used. The basic idea is that, rather than a person’s existence not telling us anything about whether conceiving them was easy or hard, it can be shown mathematically that it was most likely easy. 

 “The Conception analogy stuck in my mind and ultimately I came to believe that the Carter argument must be wrong,” Whitmire said. “But at that point I didn't know why it was wrong.”

To tug on this thread, Whitmire developed a mathematics-based argument that builds on the analogy with the help of the so-called “old evidence problem” in Bayesian Confirmation Theory, which concerns the incorporation of newly-acquired data into existing hypotheses. 

The details are pretty complicated, but the gist is that while Carter holds that old evidence (i.e. the existence of life on Earth) has no influence on the probability of its occurrence elsewhere, Whitmire’s paper attempts to show that, actually, this “old evidence” does in fact increase the probability of it occurring in the first place. Under this novel framework, both abiogenesis on Earth and Whitmire’s conception are more likely to have been easy than hard, which suggests that life on other planets may be common.

These ideas are a bit heady, and Whitmire notes that they might not actually have that much of an impact on anyone’s hopes or doubts about the probability of alien life existing somewhere in space.

“My opinion is that what many scientists believe about life and intelligent life in the universe is almost political or psychological,” Whitmire said. “If they want to believe life is rare they will point to the Carter argument or some other argument, like the statistical improbability of abiogenesis, to make their case.” 

Likewise, Whitmire added that those who want to believe life is abundant can find evidence for that position in other studies, including his new paper. 

“There is no reason that I know of (outside of my paper) for any objective optimism about abiogenesis being easy, yet this is the belief of most astrobiologists in spite of the Carter argument,” he said. “Perhaps my paper will give some objective credence to this subjective belief. That said, I think that arguments like mine and Carter's have some influence but the dominant attitude is that since none of the arguments are 100 percent, only future observations will decide.”

Fortunately, we live in an era packed with exciting missions focused on the search for extraterrestrial life, both inside our solar system and beyond it. NASA’s Perseverance rover is currently searching for signs of ancient life on Mars, and future missions may scout out Jupiter’s moon Europa or Saturn’s moon Enceladus, which are both considered to be potentially habitable. Next-generation observatories, including the James Webb Space Telescope, have the capacity to spot signs of life (or biosignatures) on planets in other star systems, and astronomers are scanning the skies for messages from technologically advanced aliens. 

Of course, all of these efforts could come up short in the search for life beyond Earth. But just one detection of life beyond our planet—even if it were microbial, or long-extinct—would validate Whitmire’s new argument that abiogenesis is not rare in the universe.

“If life (or past life) were found anywhere in our solar system or beyond that would statistically guarantee that the origin of life is very easy and life can be expected to be abundant throughout the universe,” Whitmire concluded. “That's why so much effort is being put into missions to Mars and ultimately Europa, and elsewhere. If life is easy, then the James Webb telescope may find extrasolar planetary biosignatures in the not-too-distant future.”