We know for a fact that the existence of proteins, enzymes, and DNA makes possible (some would say inevitable) the evolution of the living organsims that populate the Earth -- not necessarily the ones we know of, but certainly something like it.
For instance, the DNA code for amino-acids is arbitrary, and could easily be as different from what we have, as Chinese is from the hieroglyphics of ancient Egypt.
But there is a school of Evolution Doubters, who think that the chemical complexity of DNA, ribosomes, enzymatic activity, and the mitochondrial processes, had to have been explicitly and individually designed by a creator Intelligence. Well, for one thing, if the creator Intelligence is some extraterrestrial non-God Being, how did It come to Be? For another, what's so intelligent about a Creator that has to fiddle with Its Creation?
A more respectable view of Intelligent Design is to be found in Baruch Spinoza's writings and Thomas Paine's "Age of Reason".
Both of these philosophers attribute the Laws of the Universe quite frankly to the one true God. They therefore reject, as did the skeptic David Hume, the idea of miracles, Divine Intervention, interference with the Laws of Nature, on the grounds that an omnipotent God does not design a Universe that needs arbitrary changes. If God wanted Life to arise, God would design the Laws of Nature so that it would arise Naturally!
The gods of Olympus had no such responsibility. They seem to have been stuck with the same natural restrictions as the Greek humans, except that they could occasionally override them. Zeus could hurl thunderbolts, but it was Apollo's chariot that carried the Sun across the sky. We know that it is the sun that provides the energy for the lightning, but the Greeks didn't.
Whether we agree or not that an Intelligent Designer is a logical necessity, we are left with a gap. We know that enough energy impinges upon the Earth to supply the needs of living organisms. We know that it happened. We know that the first living organisms left descendants, and that the sequence of these descendants evolved into the myriad of species now living, and even more myriads now extinct. We find that Natural Selection suffices to explain this evolution. But how do we explain the difference in complexity between proteins, nucleic acids, and so forth, and the comparatively simple compounds that we presume existed on the primeval Earth?
It seems to me that we are reasonably entitled, or even compelled, to conclude that before the obviously organic evolution of a wider variety of more complex living things from the initial population that came into being, there must have been a sort of chemical evolution of the complex molecules for which no fossil evidence can as yet be imagined. A good many arbitrary, accidental advantages must have led to the total dominance of all the left-handed and right-handed forms of these organic molecules, but that's no more difficult to explain than why a block balanced upon a knife edge falls to left or right, and takes everything with it.
It even seems to me that RiboNucleic Acid is probably not the only polymer capable of encoding life. Ribose is a monosaccharide, a simple sugar, one among several. Galactose is another.
Is it possible that life exists Out There encoded by Galacto-Nucleic Acid?
Well, maybe ribose has a subtle advantage. But it certainly doesn't have to be right-handed.
Suppose we define a living organism as a complex entity capable of using an external source of energy to cause its own reproduction, where reproduction means making a near copy of the individual organism, similar to it and having a range of properties in common with other organisms like the parent or parents.
We might define an intelligent being as any entity capable of communicating with another intelligent being. Any animal with a language, however primitive, is by this definition intelligent. Turing defined an Artificial Intelligence as any artifact capable of communicating in print in a fashion that a skilled human could not distinguish from the fashion of another human. But this idea was carried much further by the brilliant cosmologist Fred Hoyle in his fictional story "The Black Cloud", wherein the extra-terrestrial communicated with a group of scientists using English speech, and was in fact powered by purely electromagnetic energy, not having a chemical basis at all. The Black Cloud was the entire property of this Being, and there was only one of him/her/it there, and I do not remember any mention of the method of reproduction if there was one.
Crystals and snowflakes, and presumably clouds and mineral deposits, are not supposed to qualify. We might say that there is nothing about a given snowflake or cumulus cloud that tends to cause snowflakes or clouds nearby to resemble it more closely than others.
Aluminosilicate condensations, clays, come in a myriad of forms, and can interact with simple organic molecules. (That's 'organic' in the chemist's sense.)
There is a school of thought that there may be aluminosilicate chains that could favor the production of their own peculiar crystal structure over that of near relatives.
But here's the strange part. If we accept my conclusion that the existence of a supply of energy is what powered the evolution of pre-living organic chemistry, does it not suggest that similar processes could develop anywhere that such a combination of potential chemical complexity and stellar energy is available?
We know nothing of what chemistry can go on within the atmosphere of Venus, nor yet on or within Jupiter or its moons. It is arrogant to suppose that only our (carbon) chemistry can reach 'organic' complexity. Maybe there is life on Titan, of a sort that is as unimaginable to us as a neutron star would have been to Ezekiel or to the author of the abominable "Book of Revelation."
For those who haven't heard of them, there are
Sirius, the brightest star in our sky, has a companion which is visible only in powerful and near perfect telescopes, but is of comparable mass and temperature. We know its temperature from its spectrum. So per unit area of its surface it must be as bright as Sirius, but it gives off far less light than Sirius. So it must be of amazingly small radius, and therefore correspondingly high density.
Quantum physics supplies the explanation, that every electron is pressed by gravity as close as possible to all the others. The massive atomic nuclei, which have a much smaller radius (!!!) wander freely around among these packed electrons. Occasional collisions of the nuclei provide enough nuclear fusion energy to maintain the high temperature and supply the light.
But a neutron star is the gravitational collapse of a star to the point where even the electrons and protons are forced together, in other words they merge to become neutrons, and the entire star resembles a single inordinately large atomic nucleus.
Four such stars in quick succession were actually discovered by radio astronomers at Oxford University, although what they seemed to have discovered were stars from which digital microwave signals seemed to be coming.
Cautiously, these were referred to as four 'pulsars',
When the research of the radio astronomers was supplemented by the discovery that the same, unmodulated, signals were being sent in the X-ray bands as well, the (formerly) obvious hypothesis that intelligent beings were sending these signals was abandoned. Intelligent beings do not broadcast content-free signals at such inordinate power levels.
The parsimonious explanation is that each star is a body with the density of an atomic nucleus, a mass comparable to that of our Sun, and a radius no bigger than a fair-sized city. The apparently digital signal, beeping hundreds of times a second, is like the beam of a lighthouse spinning at thousands of rpm, which is what the star and its magnetic poles are doing.