Aliens, where are you? Are we alone in the Universe
Without intelligence, there is no intelligent life, everyone knows that. So it all boils down to a simple question: is intelligence the natural result of natural selection or an improbable accident? Our evolution shows that many key developmental outcomes — such as intelligence, complex organisms, equally complex cells, photosynthesis, and life itself-were unique, one-time events, and therefore highly unlikely. According to one theory, our evolution is like winning the lottery. Is anyone in the Universe as lucky as we are?
The Milky Way has more than 100 billion stars, and there are a trillion galaxies in the visible part of the Universe. And this is only a tiny part of the Universe that we can physically see. In theory, a huge number of stars and planets fly in space — there must be life somewhere. So where is everyone? This is the Fermi paradox-the absence of visible traces of the activities of alien civilizations, which for 13.8 billion years of the Universe's development should have settled here and there for a long time.
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Let's say there are intelligent beings. Can intelligence develop according to some global standard plan? We can't study extraterrestrial life to answer this question, but we can study 4.5 billion years of Earth's history.
If you" rewind " evolution back, you can find an interesting fact: sometimes different types of organisms independently acquire similar characteristics. This is called convergent evolution. In a number of swimming reptiles, penguins, and some marine mammals, the shape of the body and forelimbs in the course of evolution has acquired convergent similarities with the shape of the body and fins of fish. In armadillos and female cockroaches of a number of species, the body is covered with a large number of hard shields, and they curl up into a ball when in danger. Eyes developed not only invertebrates, but also in arthropods, octopuses, worms, and jellyfish. Vertebrates, arthropods, octopuses, and worms independently acquired jaws. So, somewhere in the Universe, evolution could have worked the same way as we do?
One modern theory, called the unique Earth hypothesis, States that multicellular life may be extremely rare due to the possible exclusivity and rarity of earth-type planets. It claims that a number of improbable coincidences made possible the emergence of complex forms of life on Earth.
Evolution on our planet is extremely slow. Photosynthesis developed a billion and a half years after the formation of the Earth, complex cells — almost three billion years, complex animals — four billion years. Human intelligence appeared four and a half billion years after the formation of the Earth. That these extremely useful changes have taken so long to evolve implies that they are, I'm sorry, incredibly improbable.
Imagine that intelligence depends on a chain of seven unlikely events: the origin of life, the appearance of photosynthesis, complex cells, gender, complex animals, skeletons, and intelligence itself. Each of them has, let's say, a ten percent chance of development. The odds of developing intelligence are one in 10 million. But it's not that simple. Complex adaptations maybe even less likely. Photosynthesis requires a number of changes in proteins, pigments, and membranes. The appearance of animals was also preceded by a complex process, accompanied by a chain of random metamorphoses. Therefore, the chances of each of the seven events developing are barely 1%. If this is the case, intelligence will only develop on 1 in 100 trillion inhabited worlds. So we may actually be the only intelligent life in the galaxy, or even in the visible universe.
Proponents of the opposite point of view insist that the requirement of the existence of terrestrial conditions for the existence of life indicates the so-called carbon chauvinism-an excessively narrow view of nature, excluding from consideration life forms whose biochemistry is fundamentally different from the biochemistry of terrestrial organisms. This is still a theory that has not been confirmed by anyone. But the scientific community is well aware of extremophiles-life forms that can retain the ability to reproduce after being in extreme conditions (to withstand high-temperature changes, pressure, adverse environment). This suggests that life can be born and preserved in conditions far from earth. But again, there is no practical confirmation of the existence of extremophiles outside of Earth, and certainly no hint of intelligent life.