Does the Slow Pace of Evolution Mean That ET Life Is Rare?That’s the contention in a recent paper by astrobiologists at Oxford’s Future of Humanity Institute
In a new paper, researchers affiliated with Oxford’s Future of Humanity Institute use the assumptions we make about the evolution of life on Earth to estimate the likelihood of it happening the same way elsewhere. And the numbers do not look good. As a science writer puts it:
There are countless naturally occurring, but extremely lucky ways in which Earth is special, sheltered, protected, and encouraged to have evolved life. And some key moments of emerging life seem much more likely than others, based on what really did happen.Caroline Delbert, “Intelligent Life Really Can’t Exist Anywhere Else” at Popular Mechanics
In the paper, the Oxford group concludes,
It took approximately 4.5 billion years for a series of evolutionary transitions resulting in intelligent life to unfold on Earth. In another billion years, the increasing luminosity of the Sun will make Earth uninhabitable for complex life. Intelligence therefore emerged late in Earth’s lifetime. Together with the dispersed timing of key evolutionary transitions and plausible priors, one can conclude that the expected transition times likely exceed the lifetime of Earth, perhaps by many orders of magnitude. In turn, this suggests that intelligent life is likely to be exceptionally rare. Arriving at an alternative conclusion would require either exceptionally conservative priors, finding additional instances of evolutionary transitions, or adopting an alternative model that can explain why evolutionary transitions took so long on Earth without appealing to rare stochastic occurrences…Andrew E. Snyder-Beattie, Anders Sandberg, K. Eric Drexler, and Michael B. Bonsall. The Timing of Evolutionary Transitions Suggests Intelligent Life Is RareAstrobiology. ahead of print http://doi.org/10.1089/ast.2019.2149
The paper is open access.
In a 2018 paper, also open access, some of the authors took aim at the Drake Equation, which has been used for decades to predict that there are many alien civilizations: “When the model is recast to represent realistic distributions of uncertainty, we find a substantial ex ante probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it.”
One problem with the Drake Equation, pioneered by cosmologist Frank Drake and popularized by Carl Sagan, is outlined at Cosmos:
The problem with the way the equation is usually wielded, the researchers argue, is that the parameters assigned to most of the various elements represent simply best guesses – and those guesses, furthermore, are heavily influenced by whether the person making them is optimistic or pessimistic about the chances of intelligent life existing. The result, they note, often involves well-estimated astronomical numbers multiplied by ad hoc figures.Andrew Masterson, “Stop looking for ET” at Cosmos (June 19, 2018)
In short, the Oxford group’s basic contention is that, in a universe that is a bit over 13 billion years old, on a planet that is roughly 4.5 billion years old, it took all this time for random processes of evolution to result in life forms like ourselves that scan the skies for other civilizations. Then the likelihood of such a favorable series of chance events happening often—or maybe ever again— is slim.
But wait. What if evolution is not random? In Miracle of the Cell (2020), biochemist Michael Denton argues that even the elements that make up our universe are fine-tuned to produce life. If he is right, life could, of course, have gotten started in many other parts of our universe, using the same elements and following the same general patterns and laws. Here’s a free excerpt from the book.
And here’s a bit of Denton’s thinking on how water, for example, promotes life:
Maybe the development of life is not an accident. In that case, the odds of it starting elsewhere are definitely better. At any rate, we shall explore and we shall see.
Note: The abstract photo of a galaxy is by César Porreca on Pexels.
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