Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Life on Earth uses carbon-based molecules and a base-4 genetic code. Is this part of the definition of life? Is it possible for a living being from another planet to be made of something else and be encoded in a different kind of code, or life is possible only for carbon-based molecules and base-4 genetic codes?
There are simple chemical properties that made carbon-based molecules more efficient for creating the kind of life that prospers on Earth. It is, in fact, relatively easy to prove that no other kind of molecules could provide such an effective medium for the creation of evolving, reproducing and growing bodies.
Nonetheless, it is not clear yet if life “has” to be based on carbon, if non-carbon forms of life are possible.
Humans have built robots made mostly of metal and copper that are capable of reproducing, growing, communicating and so forth, i.e. that satisfy the ordinary definitions of life. This is a very simple example of life that does not use Carbon-based molecules and water. If it is possible on Earth itself, it is hard to believe that non-Carbon life is impossible anywhere in the universe. It is not easy to determine which one is more likely to "spontaneously" arise in nature, an eye or one of these robots. (The "spontaneously" is in quotes because nothing is truly spontaneous: an eye is the product of natural forces just like a robot is, so far, the product of some human design).
Most calculations of the probabilities of carbon-based life are done by scientists who are biased by the fact that they themselves are made of carbon-based molecules. Earthly scientists (made of carbon-based molecules) do not calculate the odds that a robot (made of steel and copper) or some other form of life could emerge in a different kind of planet or star, where, for example, some odd natural phenomena produce stainless steel and copper wires by the millions.
Most Earthly scientists who talk about "another form of life" end up talking about the Earthly form of life (and therefore proving that carbon-based life is the only one possible).
The truth is that is a bit premature to claim that only carbon-based life is possible in this universe.
Also, it is relatively easy to build purely software systems that exhibit whatever property one ascribes to life. These software systems do not use Carbon-based molecules or water: in fact, they use no chemistry at all.
The real issue is that biologists do not agree on a definition of life. If we don't know what life is, it is hard to discuss... what life is.
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