Sunday, November 07, 2004

Persistence



One way to look at evolution is as the product of persistence through time. I don't mean persistence in the common sense of "keeping on trying", although there's plenty of that in evolution - I mean that some things persist through time, they last, and some things don't.
Back when the world was a chemical soup, certain of these chemicals dissolved, while others showed a tendency to stabilize and to persist as time went on. They bound with other chemicals to form even longer-lasting compounds, and over time, given the sorts of conditions that existed on earth in its earliest days, they formed the very complex molecular structures known as proteins.

This process is not speculative - it has been reproduced in the laboratory under conditions similar to conditions on Earth in its earliest days.

A fuller discussion of the transition from chemicals to complex molecules to proteins can be found at: http://www.biologie.uni-hamburg.de/b-online/e41/41.htm

But really evolution is about what persists and what doesn't. If something does not persist through time, we don't see it. It went. It's gone. It's extinct. If something does persist, it lasts, it's not gone, it carries on, it survives. The battle for survival is really a testing of what works to allow an entity to persist and not to dissolve or vanish.

So some things have come down to us from the dawn of the Earth because they have solved the riddle of persistence. They have "learned" how to survive. Even the smallest molecule can "learn" in the sense that it will do the things that permit it to persist, because if it doesn't, it ceases. This is not to argue that elements and atoms and molecules are intelligent and make decisions to survive. It just means that if they do not do the things that allow them to persist, they just don't persist and are gone.

It's important to understand this somewhat mindless process of chemical elements stewing about for millions of years, and eventually forming increasingly complex compounds that are different because they persist. The building blocks of life are elements like carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. From these there evolved sugars, amino acids, nucleotides, fatty acids, phospholipids, vitamins and coenzymes. From these evolved proteins, lipids, carbohydrates and nucleic acids. Eventually, the process produced very complex proteins like RNA and DNA, that persist because they have "learned" how to reproduce themselves. They behave in ways that result in their persistence.

The evolution of proteins is discussed here: http://www.utdallas.edu/~cirillo/nats/day18.htm
Again, remember that "learning" here is just doing the "right" thing to survive, and surviving is more than just existing, it is also a set of behaviours that will result in the chemical compound or molecule or whatever, the entity that displays such behaviour, persisting through time.

So to this point I hope I've shown that even chemicals can "learn" in the sense that they will do the sorts of things that result in their persistence. They do this unconsciously, but if they don't do the "right" sorts of things to survive - they don't.

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1 comment:

Anonymous said...

hi, just randomly surfed on.

perhaps everything about life is evolution, a mere chanced occurence at survival and existence. and then perhaps there is some magical wonder how life permutates itself.

i prefer to believe that life is something beyond the simple mechanics of elimination. the magnitude of life (if you could see the world with special goggles that detects enzymatic reaction and thus vitality red, you'd see the globe as a big bright red dot i think) is just mind boggling.

well, anyway, just a blossoming thought. can't really articulate it well. my head hurts from an exam i just had. biology paper's tomorrow. wish me luck!

hope the comment makes you want to write more tho =D