As astrophysicists have calculated the size of the universe, we have become more aware of how rare it would be for us to be alone in such vastness. However, biology still struggles to fit the pieces that give rise to life, so science has begun to consider whether it might be true that we are alone. This is why bestselling astrophysicist Mario Livio has teamed up with molecular biologist and 2009 Nobel Prize in Medicine winner, Jack Szostak, to publish Life and Cosmos: Is Earth an Exception? (Ariel Editorial).
"Even if we were an exception, isn't the universe large enough for there to be many exceptions?"
"The answer is yes and no," Livio responds. "In our galaxy, we may have billions of planets similar to Earth, and there are up to two trillion galaxies like the Milky Way in the observable universe. The problem is that having only known one type of life, we don't know what the probability is of it starting, even if the conditions are suitable. We have no idea. We would like to think that there is life somewhere else, but perhaps the probability of it arising is so small that, even with these large numbers, it may not exist anywhere else. That's why we are trying to find out in a laboratory if creating life is easy or difficult."
"What will come first, creating life on Earth or discovering it elsewhere?"
"The laboratory work will come first," Szostak explains. "But it will be a very simple type of life, a chemical system that can start Darwinian evolution. What astronomers are looking for is relatively advanced life in terms of biochemistry because it must transform the planet to be detectable. And the technical challenges are enormous. By the 2040s, we will have the ability to study about 100 extrasolar planets in search of signs of life, which is still a small number. And if we find nothing, we can say, 'Okay, even when the conditions are suitable, less than one in a hundred develops life.' But if we are very lucky, or life is really very common, maybe 100 will be enough."
"Finding intelligent life seems increasingly difficult"
As physicist Philip Morrison once said: "The probability of success is difficult to estimate, but it approaches zero if we never undertake the search." Discovering whether life on Earth was a fortuitous accident or a chemical imperative remains pure speculation for now, but unlike other universal goals such as world peace or curing cancer, Livio and Szostak believe that this discovery "seems to be on the verge of being achieved."
Even with thousands of potentially habitable planets, we still do not know the probabilities of life chemically "taking off" because we do not fully understand that process. Szostak updates us with chapters that mix the chemical composition of early Earth with volcanoes and asteroid impacts to see how the reactions that led to nucleic acids of genes, amino acids of proteins, and lipids of cell walls could have been triggered. "There is a lot of chemistry involved," summarize the authors.
For now, what is known is that life is more likely to occur in "scenarios rich in iron and phosphates with wetting/drying and freezing/thawing cycles." This makes thermal waters in volcanic areas and craters created by asteroid impacts the most likely scenarios for the miracle to happen.
The authors are also clear that the laws of physics and chemistry have not changed since the formation of the Sun, so any model on the origin of life must be consistent with these laws. Biologists and chemists have managed to demonstrate, for example, that the basic components of living beings can be generated from cyanide, which does not say anything too good about our own nature.
In Life and Cosmos, the authors take a good walk through the universe, starting with the solar system, to recognize its limitations for life. Mars and Venus, for now, have been disappointing, but hopes lie in the water oceans of Jupiter and Saturn's moons. Titan has a dense atmosphere, rivers, rain, and seas, which, although made of methane and not water, lead the authors to imagine exotic life forms based on other solvents.
Although we are sending probes and pointing telescopes towards other worlds to find signs of what we consider "evidence of life," the authors acknowledge that it could be very different from terrestrial life, and even unnatural. "The unnatural is also natural," summarize the authors quoting not a biologist, but the playwright Johann Wolfgang von Goethe. More or less what the popularizer Carl Sagan called "carbon chauvinism."
"If we see oxygen in the atmosphere of another planet, it is only a possibility of there being life, not proof of life."
"And how do we find unnatural life?"
"For now, we are looking for the life we know, the one that emerges from chemistry. The question is that this life must have transformed the planet, especially its atmosphere, for us to see something, and that is a very difficult problem. There is also debate about what the correct signal would be. That is, if we see oxygen in the atmosphere of another planet, it is only a possibility of there being life, not proof of life."
The advent of AI has opened the doors to the possible existence of technological civilizations in the universe. But the problem again is finding them. "There are searches, especially in terms of radio signals, and things like that," Livio points out. "But if the probability of another civilization existing is low, the probability of it being in a similar evolutionary state to ours is even lower. It is much more likely to be a billion years more advanced or less advanced. Now, if it is a billion years less advanced, it is not a technological civilization. But if it is a billion years more advanced, maybe it is so much that even if they send signals to tell us that we are not alone, we wouldn't understand them, or we wouldn't recognize them as signals. So it's complicated."
"In any case, it seems clear that our evolution tends towards a technological civilization."
"There is a concept called the great filter, which says that perhaps there is a great obstacle for intelligent civilizations, which could have been in our past, and that we managed to overcome and others did not, and that is why we are very rare, or even the first. But there is also the possibility that this great filter is in our future, which would mean that at some point we will destroy ourselves or something like that. If you look at the world today, the possibility of self-destruction is possible."
One of the most intriguing aspects of this issue is consciousness. Philosophers, psychologists, neuroscientists, and computer scientists have vehemently debated whether this is an exclusive property of organic brains, like ours, or if machines could develop a "true personality." So far, we have not been able to determine if consciousness is an emergent property, that any sufficiently advanced, sophisticated, and complex computer will ultimately acquire. "If this were to happen, we would have to accept its future hegemony, both on our planet and elsewhere in the universe, as an inevitable consequence of evolution, in the broadest sense of the term," Livio points out.
According to the authors, if beings after humanity made the leap and became inorganic minds, they would not need warm ponds or atmospheres to survive. They might even prefer a gravity-free environment (i.e., outer space), especially if they are interested in building large artifacts. "Searching for intelligent life on habitable exoplanets would be a waste of time because it is possible that non-biological brains develop capabilities in space that humans cannot even imagine," says Livio.
Things get a little more complicated when we think about quantum computers. "The ability, intensity, and memory that biological nervous systems, like those possessed by human beings, can reach will undoubtedly be widely surpassed by the dazzling meditations that the AI-based machines will be capable of," explains Livio.
It is possible that the type of organic intellectual capabilities to which we humans are accustomed is only a brief phase in evolution, before machines take control. If such a development had occurred in the case of intelligent aliens, it would be very unlikely that we would manage to surprise them in the short time they would have been confined to organic bodies. "Therefore, it is most likely that if we manage to detect a technologically advanced extraterrestrial civilization, it consists of electronic beings, and the dominant creatures are not of flesh and blood," concludes Livio.
According to the authors, if beings that came after humanity made the leap and became inorganic minds, they would not need warm pockets or atmospheres to survive either. They might even prefer a gravity-free environment (i.e., outer space), especially if they are interested in building large artifacts. "Searching for intelligent life on habitable exoplanets would be a waste of time, because non-biological brains may develop capabilities in space that humans cannot even imagine," says Livio.
Things get a little more complicated when we think about quantum computers. "The ability, intensity, and memory that biological nervous systems, such as those possessed by humans, can achieve will undoubtedly be vastly surpassed by the dazzling meditations that AI-based machines will be capable of," explains Livio.
It is possible that the type of organic intellectual abilities that we humans are accustomed to are only a brief phase in evolution, before machines take control. If such a development had occurred in the case of intelligent aliens, it would be highly unlikely that we would be able to surprise them in the short period of time that they would have been confined to organic bodies. "Therefore, it is most likely that if we manage to detect a technologically advanced extraterrestrial civilization, it will consist of electronic beings and the dominant creatures will not be flesh and blood," concludes Livio.
-And if they detect us. Would they be hostile, as Stephen Hawking thought aliens would be?
-We don't know, and neither did Hawking. But we evolved through natural selection: Darwinian evolution. And that encourages competition and a certain aggressiveness. Machines will probably not evolve through natural selection, so perhaps they will be kinder. But Darwinian evolution also leads to cooperation, which is a very advantageous trait.
-Perhaps curiosity is also a human trait and they are not interested in us at all.
-I think there are already people trying to design AI systems that are curious and try to develop new hypotheses and propose new experiments. That could happen. What we still don't know is how consciousness arises. We don't know if it's an emergent property, which means that any sufficiently sophisticated system will develop it. If they do develop it, they will also be curious, but if they lack perception of themselves and their surroundings, it wouldn't matter how intelligent they might become, because we would consider them what philosophy calls zombies.