Intelligent life in the Universe could be far more widespread than previously imagined.
A new study has just shaken up a well-known theory, the "hard steps" theory, by explaining that the emergence of complex life might not just be a matter of luck, but rather a natural consequence of the conditions present on certain planets.
A team of researchers from Penn State University has created a model that challenges the idea that the emergence of intelligent life is an extremely rare event. According to them, the evolution of humanity on Earth could be the logical result of specific environmental conditions, which would increase the chances of finding intelligent life elsewhere in the Universe.
The "hard steps" theory, proposed in 1983 by physicist Brandon Carter, argued that the evolution of intelligent life was highly improbable. It was based on the time it took for humans to appear on Earth compared to the total lifespan of the Sun. But this new study offers a different perspective: the changing environmental conditions of Earth would have played a key role in the evolution of life.
The researchers explain that important milestones, such as the appearance of oxygen in the atmosphere, created "habitability windows" that allowed the development of complex life forms. This means that the emergence of intelligent life could be a more predictable process and less dependent on chance.
This study, published in the journal
Science Advances, combines knowledge from geobiology and astrophysics to provide a new understanding of the evolution of life. The researchers plan to test their model by studying the atmospheres of exoplanets to search for signs of life (biosignatures) and by analyzing the conditions necessary for the evolution of life.
The team also suggests that major evolutionary innovations, such as oxygenic photosynthesis (which produces oxygen) or the emergence of multicellular organisms, might not be unique events. This opens up the possibility that life forms similar to ours exist elsewhere in the Universe, making the search for extraterrestrial life even more exciting.
Finally, this new perspective challenges our place in the Universe. It suggests that the emergence of intelligent life might not be the result of a series of improbable coincidences, but rather a natural process, dictated by the environmental conditions of planets.
What is the "hard steps" theory?
Proposed in 1983 by physicist Brandon Carter, the "hard steps" theory argued that the evolution of intelligent life on Earth was a highly improbable event. It was based on the time it took for humans to appear compared to the lifespan of the Sun.
According to this theory, key stages of evolution, such as the origin of life, the development of complex cells, or the emergence of human intelligence, were rare and improbable events. This meant that the probability of finding intelligent life elsewhere in the Universe was very low.
But this new study challenges this idea. It suggests that the evolution of complex life might be less a matter of chance and more a natural consequence of the changing environmental conditions of Earth.
How do environmental conditions influence the evolution of life?
Environmental conditions play a crucial role in the evolution of life. For example, the appearance of oxygen in the atmosphere, thanks to photosynthesis carried out by microbes and bacteria, allowed the development of more complex life forms.
This study shows that changes in nutrient availability, ocean temperature, water salinity, or oxygen levels in the atmosphere created "habitability windows" throughout Earth's history. These conditions allowed key stages of evolution to occur, ultimately leading to the emergence of intelligent life.
By better understanding how these conditions influence evolution, researchers hope to predict where and how life could develop on other planets, thereby increasing the chances of discovering extraterrestrial life.