Since the heliocentric hypothesis has triumphed over the geocentric hypothesis, the Copernican principle has prevailed, namely, the simple fact that we have nothing special. If this principle was a universal principle, of course, then we could think that the Universe is full of earths and that these earths are inhabited by living beings. Now, the results of astronomical research in recent decades tell us that the Universe is actually full of planets, that among them, in a minority, there are earths, but the conclusion that there are living beings on them, perhaps evolved as more than us, rests on nothing. To reach this conclusion, we would have to demonstrate in the laboratory that life originates easily, but we have not succeeded in doing that or find planets on which life exists. Today, our position can oscillate between those of de Duve and Monod without the risk of being wrong. The origin of life is possible first if there is an energy source, i.e., an environment out of thermodynamic equilibrium. Life on Earth is due to sunlight, which is captured by living forms, gives rise to a chemical imbalance in those living forms and which gives rise to the food chain. However, there are organisms that can also live in a strong lack of solar energy, such as in the black fumarole environments that we described in Chap. 4 . Energy linked to volcanism or plate tectonics is another source of energy for life. When there is a lack of balance, this generates a flow of energy that living beings skillfully use and dissipate. The complexity of life on Earth is based on reproduction, which triggered evolution by natural selection. On this basis, there is therefore the existence of individuals who interact with each other, and individuals exist because cellularization has developed during evolution, i.e., the individual is composed of cells. The life that exists on Earth is based on these two pillars: the existence of thermodynamic imbalances and cellularization, and the element on which everything rests is the chemistry of carbon. Assuming that life exists in the Universe, one might ask whether there could be life that is based on other pillars, namely, life that is not based on carbon and water. Life requires elements that can give rise to large molecules, some of which are capable of storing information, such as RNA and DNA. The first condition for life beyond carbon is that the element on which life is based is abundant enough and capable of creating complex and stable molecules. There are 91 elements present in nature, and those that could play a role in the formation of life must be stable and able to form at least three covalent bonds, i.e., chemical bonds in which two atoms share pairs of electrons. Two bonds are necessary for the element to form bonds with itself and other elements and form long chains or rings. The remaining bonds serve to bind with other elements and create structures capable of conveying information. The elements that meet these requirements are as follows: the elements that form three bonds: boron, nitrogen, phosphorus, arsenic, and antimony; and the elements that form four bonds: carbon, silicon, germanium, and tin. As mentioned, a good quantity is also needed, and in the Universe, the most abundant among these are carbon, nitrogen and silicon. Among these three, carbon is the one that has the greatest ability to form covalent bonds with itself and with other elements and form stable and long chains (e.g., proteins and nucleic acids). Furthermore, nucleic acids have a sort of skeleton with negative charges, which, by repelling, keep them stretched out so that the change in the nucleotides does not affect the structure of the DNA. Instead, proteins have no charge, so they can fold. These characteristics should also be respected by a type of life on the basis of elements other than carbon.

Carbon Chauvinism?

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发表日期：

2025年

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Antonino Del Popolo

摘要

Since the heliocentric hypothesis has triumphed over the geocentric hypothesis, the Copernican principle has prevailed, namely, the simple fact that we have nothing special. If this principle was a universal principle, of course, then we could think that the Universe is full of earths and that these earths are inhabited by living beings. Now, the results of astronomical research in recent decades tell us that the Universe is actually full of planets, that among them, in a minority, there are earths, but the conclusion that there are living beings on them, perhaps evolved as more than us, rests on nothing. To reach this conclusion, we would have to demonstrate in the laboratory that life originates easily, but we have not succeeded in doing that or find planets on which life exists. Today, our position can oscillate between those of de Duve and Monod without the risk of being wrong. The origin of life is possible first if there is an energy source, i.e., an environment out of thermodynamic equilibrium. Life on Earth is due to sunlight, which is captured by living forms, gives rise to a chemical imbalance in those living forms and which gives rise to the food chain. However, there are organisms that can also live in a strong lack of solar energy, such as in the black fumarole environments that we described in Chap. 4 . Energy linked to volcanism or plate tectonics is another source of energy for life. When there is a lack of balance, this generates a flow of energy that living beings skillfully use and dissipate. The complexity of life on Earth is based on reproduction, which triggered evolution by natural selection. On this basis, there is therefore the existence of individuals who interact with each other, and individuals exist because cellularization has developed during evolution, i.e., the individual is composed of cells. The life that exists on Earth is based on these two pillars: the existence of thermodynamic imbalances and cellularization, and the element on which everything rests is the chemistry of carbon. Assuming that life exists in the Universe, one might ask whether there could be life that is based on other pillars, namely, life that is not based on carbon and water. Life requires elements that can give rise to large molecules, some of which are capable of storing information, such as RNA and DNA. The first condition for life beyond carbon is that the element on which life is based is abundant enough and capable of creating complex and stable molecules. There are 91 elements present in nature, and those that could play a role in the formation of life must be stable and able to form at least three covalent bonds, i.e., chemical bonds in which two atoms share pairs of electrons. Two bonds are necessary for the element to form bonds with itself and other elements and form long chains or rings. The remaining bonds serve to bind with other elements and create structures capable of conveying information. The elements that meet these requirements are as follows: the elements that form three bonds: boron, nitrogen, phosphorus, arsenic, and antimony; and the elements that form four bonds: carbon, silicon, germanium, and tin. As mentioned, a good quantity is also needed, and in the Universe, the most abundant among these are carbon, nitrogen and silicon. Among these three, carbon is the one that has the greatest ability to form covalent bonds with itself and with other elements and form stable and long chains (e.g., proteins and nucleic acids). Furthermore, nucleic acids have a sort of skeleton with negative charges, which, by repelling, keep them stretched out so that the change in the nucleotides does not affect the structure of the DNA. Instead, proteins have no charge, so they can fold. These characteristics should also be respected by a type of life on the basis of elements other than carbon.