The evolution of life on the earth to the present is indeed the result of one coincidence after another, and it is indeed difficult for so many coincidences to occur in the natural environment, but the number of galaxies in the universe is too large, even if the probability is low, this huge base is enough to support the existence of other same conditions. It may just be that they are far apart, and neither of them has the ability to discover the other.
In addition, the life on the earth, in the long evolution, has been adapted to the environment of the earth to evolve, in the same way, if there is life on other planets, it must also evolve according to the environment of the home planet where the creatures are located, so I personally think that terrestrial planets are not necessarily necessary conditions for the existence of life.
Why does life have to be the form of the Earth? Not to mention the universe, some of the life found in the deep submarine crater has extremely high temperature and high pressure sulfur concentrations, how can life survive under such conditions? Much of the discussion is based on the condition that life cannot exist on other celestial bodies, ignoring the assumption that all other life is based on the same form of carbon-based organic matter as Earth, and needs water and oxygen, if not?
First of all, you have to define what life is, in essence, this is how life is defined, it is a system that can have a clear boundary with the outside world, can exchange energy and matter with the outside world, can replicate itself. By this criterion, why does it have to be a living organism?
It took 4.6 billion years for the Earth to give rise to intelligent life like humans. Other planets may be slower, or they may be faster. It is unknown where the Earth is normally distributed, so the Earth is not of reference value. Also, in the right environment, the probability of the early stage of life is greater than imagined. Environment is the decisive factor, and probability is secondary.
It is safe to say that life will be produced as long as the environment is suitable, and this was the case in the early days of life on Earth. Human understanding of the universe is still too limited, and it is too early to conclude that carbon-based is the optimal solution. The ordinary matter we can now recognize is less than 5% of the total matter in the universe. It is difficult to say whether there is "life" in the form of dark matter and dark energy.
According to the current observation, it is difficult to say whether the earth in the solar system is the only living planet, not to mention that there are other planets, the yellow dwarfs that can be observed in the Milky Way for hundreds of thousands of light years account for only a few percent, and the red dwarfs are even less, because the brightness is too low to observe, and there are fewer planets that can be calculated at present, all by the transit method, if the ecliptic plane is not aligned, it will be invisible, the observable range will be 100 million kilometers, and Hubble will not be able to see it farther, so let alone the village, it is not as good as the house.
Therefore, life may be everywhere, but the probability of emitting suitable signs of life for earthlings to discover is extremely low. The observation range of earthlings is actually very small, and they can only infer the signs of life by observing primitive means such as regular ray signals, and the most important thing is that human beings themselves have the consciousness and ability to observe for only a few hundred years, and perhaps after thousands of years, after accumulating enough observation time, human beings will discover other extraterrestrial civilizations. In any case, signs of life are clearly rare in the universe and far away.
It's just that it's still the same sentence, the universe is too big, galaxies are all 10 to the order of magnitude of tens of powers, even the limit speed of light seems too slow, like the earth, the number of human habitable planets in the universe will not be less in terms of probability, with reasonable logic to reason, there is a certain probability that there will be a smart civilization, but the probability of a civilization meeting another civilization is too low, just like a grain of sand at the south pole of the earth to meet an ice crystal in the north pole, how many tens of thousands of years to achieve it.