Aliens (or at least intelligent ones) are rare...

Researchers from the University of Oxford have created a statistical model that shows the chances of intelligent life existing elsewhere in the Universe are slim.

It’s still unknown how abundant extraterrestrial life is, or whether such life might be intelligent. On Earth, numerous evolutionary transitions were needed for complex intelligent life to emerge, and this occurring relatively late in Earth’s lifetime is thought to be evidence for a handful of rare evolutionary transitions.

In this collaboration between the Department of Zoology’s Mathematical Ecology Research Group and the Future of Humanity Institute, researchers created a mathematical model to simulate the likelihood of the emergence of intelligent observers.

Using a simplified statistical model, researchers demonstrated that the average evolutionary transition times likely exceed the lifetime of Earth, suggesting that intelligent life in the Universe is exceptionally rare.

In addition to the evolutionary transition, the emergence of intelligent life also requires a set of cosmological factors to be in place. These include whether the planet is in the right place for water to be present, whether life emerges from the water and whether the planet itself is habitable. Most crucial in this is the lifetime of the star the planet is orbiting; if this lifetime is short in comparison to the necessary evolutionary transitions for life, then intelligent observers might never get a chance to emerge (often referred to as the Great Filter).

When increasing the number of transitions, researchers found that modelling between 3 and 7 different evolutionary steps didn’t change the overall probability of intelligent life existing, indicating how improbable it is for just three conditions to line up before the Great Filter occurs.

For intelligent life to be abundant, these prior factors would have to be exceptionally conservative, assuming much early evolutionary transitions, or an alternative model that can explain why these transitions took hundreds of millions of years without appealing to rare chance events.

Obviously, one thing that would negate this would be finding intelligent life elsewhere in the universe, as that would double the sample size and potentially dramatically change the evolutionary milestones used in this model.

Although the model is simple, it provides an initial basis for evaluating how varying biological assumptions and fossil record data impact the probability of evolving intelligent life, and also provides a number of testable predictions, such as that some biological paradoxes will remain unresolved and that planets orbiting M dwarf stars are uninhabitable.

Whilst this does make any mission seeking out new life and new civilisations seem less likely to succeed, Michael Bonsall says, ‘If life is elsewhere is expected to be this rare, then we should pay more attention to preserving our species, and our planet – it seems no one is coming to rescue us!'

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