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New research argues that the evolution of intelligent life is 'exceptionally rare', meaning civilisations like ours are extremely unlikely to exist elsewhere.
The study, which comes from scientists at Oxford University's Future of Humanity Institute, looks at the evolution of life on Earth to explore the likelihood of the same thing happening elsewhere - concluding that our chances are pretty slim, given just how rare the circumstances were for us.
Titled The Timing of Evolutionary Transitions Suggests Life Is Rare, the paper explains that life on Earth has seen a number of 'major evolutionary transitions', and that some of these have occurred just once in history - suggesting that they are rare, and in turn, so is life as we know it.
The authors say in the study: "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.
"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."
The team behind the study include mathematical ecologists, who carry out forensic mathematics of Earth's history.
For the research, they used 'a simplified Bayesian model' to work out the probability of events in Earth's history happening elsewhere.
They also refer to the work of biologist Stephen Jay Gould, who theorised that if the 'tape of life' were to be rerun, the chance becomes 'vanishingly small' that anything resembling human intelligence would occur.
In fact, the scientists calculated that, in the Milky Way galaxy, there's between a 53 and 99.6 percent chance we're alone.
Speaking to The Daily Mail, Dr Anders Sandberg of the Future of Humanity Institute said: "Our methods were basically statistics.
"We made use of the assumption that what happened on Earth is typical for what happens on other planets - not the exact times, but that there are some tricky steps life needs to get through in sequence to produce intelligent observers."
Sandberg said the team added a statistical approach that allowed them to 'get estimates of just how unlikely the steps could be', adding: "We feed in data about when things happened on Earth and a guess of how many steps there were, and in return we get the most likely levels of difficulty.
"[These] turn out to indicate that, yes, we are an unlikely planet."
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