Hi, Hoot. Welcome to EvC. I hope that you enjoy your participation here.
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This leads many biologists to conclude that life is inevitable wherever friendly conditions prevail.
Actually, the reason that many biologists conclude that life is inevitable is that it seems to easy to come about. Looking at geology, the Late Bombardment came to an end about three and a half billion years ago. Before that time, life would have been impossible: if it did come about, it would have been wiped out very quickly during the frequent impacts with bodaceously large impactors. And, in the geologic record, once the Late Bombardment came to an end, we immediately see signs of life. So it appears that once the conditions allow it, life will come about very quickly.
Of course, it is very dangerous to do statistics with only one data point. Perhaps there is something unusual about the earth, and conditions were unusually favorable to life on the early earth. Or perhaps life is unusual, but the quick emergence of life on the early earth was one of those things that are improbable, but improbably events do occur.
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Wouldn't you expect to see fresh life spontaneously occurring all over the place?
No. The conditions on the current earth are very different from the early earth. We won't necessarily see the precursors of life being able to form in today's chemical environment. Oxygen, especially, will destroy most of the suspected precursors of life very quickly. Also, there is already life all over the place; they, too, would quickly eat up the energy-rich percursors.
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And why only ONE kind of life?
Maybe there were several kinds of life, but our kind was more successful and drove the other kinds to extinction. Or maybe our kind arose first and dominated before any other kind could get a chance to form. Or maybe there were many kinds, but through exchange of metabolic and hereditary mechanisms (like lateral gene transfer), many of the different kinds kind of ended up homogenizing, so that we are the descendents of several different, independent kinds.
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Genes obey rules of language”a "symbolic" language, it appears, because DNA configurations are not stereochemical with the proteins they build.
This, I think, is the wrong way to look at it precisely because it does seem to cause some kind of confusion. Despite the use of the usual analogies to explain how heredity works, DNA is not a language, it is not a code. It is simply a chemical that takes part in chemical reactions. In the right chemical environment (like in our cells) it can catalyze its own reproduction. It can also, in the right chemical environment, catalyze the production of proteins.
I have never really understood the "DNA is a code" or "DNA is a language", except as a metaphor that kind of, sort of explains how heredity and embryonic development work. I think the best thing to do, if you really want to understand genetics, is to rid yourself of those conceptions. But I'll let the actual geneticists and biochemists weigh in on how useful the metaphor is.
Never believe anything in politics until it has been officially denied. -- Otto von Bismarck
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