New Research Suggests Alien Life May Be More Human-Like Than We Ever Imagined
We are not alone in the universe and aliens are likely to look just like us, new research suggests.
This is because boffins say that humanity may not be extraordinary but rather the "natural evolutionary outcome" for planets in general. This means that aliens evolving on distant worlds could have quite easily evolved just the same way we did, swimming about in the sea, before crawling onto land and growing arms and legs (to summarise evolution simply).
The model, which turns upside down the decades-old "hard steps" theory that intelligent life was an "incredibly improbable" event, suggests that maybe it wasn't all that hard or improbable.
Researchers at The Pennsylvania State University in the US, who led the study, said the new interpretation of humanity's origin increases the probability of intelligent life elsewhere in the universe.
Co-author Professor Jennifer Macalady said: "This is a significant shift in how we think about the history of life.
"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."
Initially developed by theoretical physicist Brandon Carter in 1983, the "hard steps" model argues that our evolutionary origin was highly unlikely due to the time it took for humans to evolve on Earth relative to the total lifespan of the sun and therefore the likelihood of human-like beings beyond Earth is extremely low.
In the new study, published in the journal Science Advances, a team of Penn State researchers argued that Earth's environment was initially "inhospitable" to many forms of life, and that key evolutionary steps only became possible when the global environment reached a "permissive" state.
For example, complex animal life requires a certain level of oxygen in the atmosphere, so the oxygenation of Earth's atmosphere through photosynthesising microbes and bacteria was a "natural" evolutionary step for the planet, which created a window of opportunity for more recent life forms to develop.
Lead author Dr Dan Mills, a postdoctoral researcher at The University of Munich, said: "We're arguing that intelligent life may not require a series of lucky breaks to exist."
Dr Mills, who worked in Prof Macalady's astrobiology lab at Penn State as an undergraduate, added: "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 central prediction of the "hard steps" theory states that very few, if any, other civilisations exist throughout the universe, because steps such as the origin of life, the development of complex cells and the emergence of human intelligence are improbable based on Carter's interpretation of the sun's total lifespan being 10billion years, and the Earth's age of around 5billion years.
In the new study, the research team (including astrophysicists and geo-biologists) proposed that the timing of human origins can be explained by the sequential opening of "windows of habitability" over Earth's history, driven by changes in nutrient availability, sea surface temperature, ocean salinity levels and the amount of oxygen in the atmosphere.
Given all the interplaying factors, the Penn team say the Earth has only "recently" become hospitable to humanity. It's simply the natural result of those conditions at work.
Study co-author Professor Jason Wright said: "We're taking the view that rather than base our predictions on the lifespan of the sun, we should use a geological time scale, 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 time scale at a planetary pace."
