Is intelligence a cosmic rarity or the natural result of planetary evolution?

A new model about how intelligent life was developed on Earth has just concluded that no. And not only that, but proposes that the appearance of humans, like that of other intelligent species beyond our planet, is practically inevitable, a logical consequence of biological and planetary evolution. The work, just published in ‘Science Advances‘, completely change our way of understanding evolution and raises new and fascinating possibilities about the existence of life in other parts of the universe.

The theory of ‘difficult steps’

For decades, the so -called ‘difficult steps’ theory (‘Hard Steps’), proposed by the theoretical physicist Brandon Carter in 1983, has suggested that the appearance of intelligent life is an incredibly unlikely event, almost a blow of cosmic luck. The theory is based on the enormous amount of time (around 4,000 million years) that humans took to appear on Earth in relation to the total useful life of the sun, which implies that the probability of similar beings to us beyond From our own planet it is extremely low. In other words, for Carter the existence of humanity constitutes a true statistical miracle.

Now, however, the study carried out by a team of researchers from the State University of Pennsylvania proposes a radically different perspective. Its model, in effect, suggests that the evolution of complex life, including human intelligence, is not as unlikely as it was believed. And that instead of a series of fortuitous events, the appearance of humanity could be the natural result of the interaction between life and its environment, a process that develops on a planetary scale.

“This is a significant change in the way of thinking about the history of life,” says Jennifer Macalady, co -author of the article, “and suggests that the evolution of complex life can have less to do with luck and more with the interaction between the interaction between the life and its environment, which opens new and exciting ways of research in our search to understand our origins and our place in the universe ».

Habitability windows

The key to this new interpretation lies in the idea of ​​’habitability windows’. The researchers argue that the primitive land was not a cozy place for many ways of life. And that environmental conditions, such as the amount of oxygen in the atmosphere, the temperature of the sea surface, the salinity of the ocean or the availability of nutrients, are crucial for the development of complex life. Let’s take oxygen as an example. Complex animals, like humans, need a certain amount of oxygen in the atmosphere to survive. Therefore, the oxygenation of the Earth’s atmosphere, a process driven by photosynthetic microorganisms and bacteria, was undoubtedly a fundamental evolutionary step for the planet. In the interpretation of the researchers, this oxygenation created a ‘habitability window’ that allowed the development of the most recent life forms, including the human.

For Dan Mills, from the University of Munich and principal author of the article, “intelligent life does not necessarily require a series of hits of luck to exist. Humans did not evolve ‘early’ or ‘late’ in the history of the earth, but ‘in their time’, when the conditions were already given. Therefore, it may be just a matter of time, and perhaps other planets can achieve those conditions more quickly than the Earth, while other planets could take even more ».

Few or many civilizations?

The central prediction of the ‘difficult steps’ theory establishes that there are very few, if there are any, intelligent civilizations throughout the universe, because the necessary steps to reach them, such as the origin of life, the development of Complex cells or the appearance of human intelligence are highly unlikely. The idea is based on the fact that the smart life on Earth emerged relatively late, when the sun already had about 5,000 million years, that is, when it was already in the middle of its existence (which is estimated at 10 billion years ). Which is an extraordinarily long temporary period.

However, the new study proposes that the moment of human origins can be explained by the sequential opening of ‘habitability windows’ throughout the history of the earth, driven by key environmental changes. Thus, and instead of using the useful life of the sun as a reference, researchers suggest using a geological time scale, that is, the time it takes for the atmosphere and the landscape to change until reaching the ideal conditions.

Jason Wright, another of the co -authors of the article, points out that the theory of difficult steps has prevailed for so long because it originated in astrophysics, the field that tries to understand the formation of planets and celestial systems. This new study, however, is the result of a collaboration between physicists and geo biologists, and unites different disciplines to create a more complete image of how life evolves on a planet like ours.

«This article,” says Macalady, is the most generous act of interdisciplinary work. Our fields were very separate, and we put them on the same page to get to this question of how we got here and if we are, or not, alone. There was an abyss, and we built a bridge ».

Try the new model

Now, researchers plan to test their alternative model, including questioning the unique status of the evolutionary ‘difficult steps’. To do this, they suggest research projects such as the search for biofirms, for example oxygen, in planet atmospheres outside our solar system. And they also propose to test the requirements for the ‘difficult steps’ to occur and determine the difficulty they really have, something that can be achieved by studying uni and multicellular life forms under different specific environmental conditions.

Beyond future projects, the team suggests that the international scientific community investigates whether innovations, such as the origin of life, oxygenic photosynthesis, eukaryotic cells, animal multicellity and homo sapiens, are truly unique events in the history of The Earth. That is, could there have been similar innovations in the past, but the evidence that they occurred was lost due to extinction or other factors?

“This new perspective,” says Wright, “suggests that the emergence of intelligent life may not be something so distant after all. And that instead of a series of unlikely events, evolution is more a predictable process, which develops as global conditions allow it. Our frame is applied not only to Earth, but also to other planets, which increases the possibility of life similar to ours in other places.

It is, therefore, a deep paradigm change that has deep implications in the search for extraterrestrial life. In fact, if intelligent life is a natural result of planetary evolution, then the probability of finding life in other parts of the universe increases significantly. The search for biofirms in exoplanets and the investigation of planetary habitability become even more relevant in this new context. The big question, therefore, is no longer whether there is life in other places, but rather, when and where will we find it?