Another path for evolution:
No, this is not about how we might have turned out differently.  It’s about a second way evolution proceeds.  Ordinarily you have DNA in cells that dictate how messenger RNA is to be assembled that dictates how proteins are made that do most of the complex work of an organism.  If you change the DNA, you change the organism.  That may lead to inheritable variation – since the new organism and it’s offspring are different – which may lead to differential survival whereby the new form is either eliminated or comes to dominate the species, and thus you have classical “new synthesis” evolution.  All of this is well accepted with massive experimental support.

Sometimes the messenger RNA is tampered with, they say “edited,” by a cell before it is used to make protein.  Why would you want to do that?  I mean assuming you are a benign, conscious, forward thinking and competent spirit of evolution.  Nope, no such animal.  It’s all chance.  But why would this editing persist?  What’s the advantage?

I take it as axiomatic that organisms tend to be struggling against their maximum complexity.  I once took a light airplane up to about two miles.  At first the climb was rapid and easy.  But as I approached 10,000 feet things began to act up.  I was traveling at a steep angle of attack, nose tilted up, with full power, but wasn’t climbing much.  I fiddled with the richness of the gas mixture, nursed the angle of attack, tried messing around with a bit of lowered flaps.  I was running out of ideas, but there was my altimeter at 9,500 feet or so stubbornly refusing to go higher.  Of course I had no oxygen mask, so my brain could not have been working well at that altitude.  With white knuckles and furrowed brow I fought on.  Then it came to me.  You adjust the altimeter to sea level barometric pressure.  That way it gives you a usable altitude.  If the weather is bad, the air pressure at any altitude is going to be lower.  On a fine day air pressure will be high.  So I reached over and cranked the adjust knob, calling for a really clear day.  Now I was looking at 10,000 feet.  Victory.  I set it back where it belonged, reduced altitude and went on with my flying practice.  I had visited my service ceiling. 

Well organisms battle against a sort of a ceiling.  You can’t increase complexity forever with the same technology (or biochemistry in this case).  So evolution calls for ever greater complexity, makes compromises between various promising directions, and eventually gets to the point where the cost of more complexity balances any readily available change.  The cost in this case means more genetic information, more mutations and more offspring that have to be eliminated in order to maintain a viable genome. 

This of course flies in the face of common superstition, which is more or less that mutation is good because it provides the raw stuff for natural selection to work on and promotes evolution.  A finite mutation rate is needed, of course, but if it could be lowered a great deal with no other cost then evolution could go farther although doubtless not so quickly.

One way to reduce mutation pressure is to use the same strand of DNA for as many things as possible.  If a critical error occurs, then the organism potentially has multiple lethal processes going on all at once.  But that means nothing.  One lethal process amounts to the same thing.  In order to use the same DNA code for multiple applications, editing the messenger RNA seems like an advantageous approach.

All of this has been known for years.

But now they say they have found (The Value of a Good Editor ECONOMST vol. 402 no. 5766 January 5, 2012 page 72 reviewing work by Sandra Garett and Joshua Rosenthal of the University of Puerto Rico) a situation where this gene editing is exploited by evolution.  The octopi that live in cold water have some differences with those that live in warm and this difference is not due to the DNA of the relevant genes, they are due to differences in editing.

This is interesting.  It is hard to believe that it has anything to do with the changes that dictate falling fertility with decreasing kinship.  Ultimately the difference probably really is due to some DNA difference or other, and that changes much too slowly for such a purpose. 

Still, in looking for a mechanism, it seems best to keep an open mind.  This process does not seem to be promising, but maybe another will be.

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