Scientists have said that in a cosmos filled with trillions of stars, intelligent alien life will form ‘in only a matter of time’.
If it hasn’t already, that is.
Many astronomers say that for life to form, ‘hard steps’ must be met within the 10 billion-long lifespan of a star.
While this sounds like a long time, in the grand scale of the universe, this is a tight deadline for life to establish – and even less for brainy humans down the line.
But a new study suggests that humans didn’t simply win the jackpot of evolution’s lottery. Rather, we’re the outcome of an almost predictable geological process.
‘We’re arguing that intelligent life may not require a series of lucky breaks to exist,’ Dan Mills, a researcher at the University of Munich who co-authored the study, said.
‘Humans didn’t evolve “early” or “late” in Earth’s history but “on time”, when the conditions were in place. Perhaps it’s only a matter of time, and maybe other planets are able to achieve these conditions more rapidly than Earth did, while other planets might take even longer.’
The ‘hard steps’ theory can be thought of as a checklist. For intelligent life to flourish, ‘improbable’ evolutionary quirks need to happen like inorganic material becoming organic, cells finding a way to replicate and DNA, the mitochondria (that famous powerhouse of the cell) and language forming.
Earth, at about 4,500,000,000 years old, is only a little younger than the4,600,000,000 years old Sun.
Under the theory, though, life came about relatively late in the star’s lifespan. Humans are a fluke in other words, the 1983 theory’s creator, physicist Brandon Carter, argued.
Mills feels differently. His study, published in Science Advances, suggests that human life didn’t emerge late but simply when the timing was right.
Jason Wright, a professor of astronomy and astrophysics at Penn State and a co-author of the paper, said: ‘We’re taking the view that rather than base our predictions on the lifespan of the Sun, we should use a geological timescale because that’s how long it takes for the atmosphere and landscape to change.
‘These are normal timescales on the Earth. If life evolves with the planet, then it will evolve on a planetary timescale at a planetary pace.’
Earth was, in the early days, completely inhospitable. The team argue that evolutionary steps only became possible when the world became ‘permissive’.
Complex animal life needs a certain level of oxygen in the air, for example, so the oxygenation of Earth’s atmosphere through photosynthesizing microbes puts the planet one step closer to intelligent life.
This is one of many ‘windows of habitability’ that suggest life is a natural consequence of planetary evolution. Others include the sea becoming salty or the sea surface temperature mellowing.
The origin of life may not have been a singular moment, too, the researchers say. ‘Could similar innovations have evolved independently in the past, but evidence that they happened was lost due to extinction or other factors?’ Penn State asked.
Moving forward, star-gazers searching for aliens should analyse exoplanet atmospheres for oxygen and other signs the planet is – or is on the road to becoming – hospitable, called ‘biosignatures’.
‘This is a significant shift in how we think about the history of life,’ Jennifer Macalady, a professor of geosciences at Penn State, said.
‘It suggests that the evolution of complex life may be less about luck and more about the interplay between life and its environment, opening up exciting new avenues of research in our quest to understand our origins and our place in the universe.’
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