A new study proposes intelligent life is more likely to emerge than previously thought, driven by planetary conditions.
The "hard steps" model (1983) suggests intelligent life is rare due to Earth's long evolution.
Photo Credit: NASA
A new study challenges the long-standing belief that intelligent life is an unlikely occurrence, suggesting that human-like evolution may be a natural outcome under the right planetary conditions. The research puts forward an alternative to the "hard steps" theory, which argues that the emergence of complex life is rare due to a series of improbable evolutionary leaps. Instead, the latest findings indicate that life evolves in response to planetary changes, making intelligent civilisations more probable than previously estimated. The study has been conducted by a team of experts, including astrophysicists and geobiologists, who assert that Earth's environmental conditions played a crucial role in determining when complex life could emerge.
According to a study published in Science Advances, the probability of intelligent life developing on other planets is higher than once believed. The research, led by Dan Mills, a postdoctoral researcher at The University of Munich, suggests that key evolutionary steps were not mere coincidences but rather responses to planetary changes. Mills explained that atmospheric oxygen levels, nutrient availability, and oceanic conditions dictated when complex organisms could thrive. He stated to Phys.org that Earth's history was shaped by a sequence of "windows of habitability" that allowed life to advance in a systematic manner.
The widely accepted "hard steps" model, introduced by theoretical physicist Brandon Carter in 1983, argues that the emergence of intelligent beings is extremely rare. It is based on the premise that Earth's evolutionary timeline was lengthy relative to the sun's lifespan, making human-like intelligence an anomaly. However, the new research, co-authored by Jennifer Macalady, Professor of Geosciences at Pennsylvania State University, proposes that life progresses at a planetary timescale rather than an astrophysical one. Macalady told phys.org that rather than relying on astronomical predictions, geological factors should be considered to understand the evolution of life.
The findings suggest that if planetary conditions determine the timing of evolution, other planets may develop intelligent life at different rates. Jason Wright, Professor of Astronomy and Astrophysics at Pennsylvania State University and a co-author of the study, said that the framework increases the probability of detecting extraterrestrial life. He added that future research should focus on identifying biosignatures in exoplanetary atmospheres, such as oxygen and other life-supporting elements.
To assess the validity of this alternative model, researchers plan to examine whether previously assumed "hard steps" in evolution were truly rare occurrences. The study outlines proposals for experiments involving both unicellular and multicellular life forms under varying environmental conditions. The team suggests further investigation into whether certain evolutionary developments, such as oxygenic photosynthesis or the emergence of eukaryotic cells, have independently occurred multiple times throughout Earth's history but were lost due to extinction events.
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