Re: Junk DNA: A hypothesis

From: Jim McGinn (jimmcginn_at_yahoo.com)
Date: 01/22/05 

Date: Sat, 22 Jan 2005 13:01:43 -0500 (EST)

Larry Moran wrote:

<snip>

> > Also, DNA harbours multiple regions such as
> > LINE-1. These act as mutagens - and are likely
> > to be directly deleterious.
> >
> > However they generate a different pattern of
> > mutations from (say) cosmic rays. They generate
> > patterns of mutations that affect different
> > regions of DNA more frequently than others. That
> > whole set-up could serve some functional purpose.
>
> There's no way that a population could select for
> enhanced deleterious mutations on the remote chance
> that some of them will be beneficial every million
> years or so. That sort of thing would require an
> intelligent designer with foresight.

False. Larry is drawing from a neoDarwinism-based
fallacy that only individual organisms can be the
focus of adaptation. In reality all that is necessary
is that populations that do, by chance, have such
sophisticated processes survive in higher numbers than
those that don't. Larry's problem (like that of all
other neoDarwinists) is that he is caught-up in a
dogmatic interpretation of Darwin's words.

> > We know that some evolution takes the form of
> > duplication and modification. Rapid elimination
> > of unnecessary non-functional genes might
> > significantly hamper this process.
>
> It might. But once again you are postulating
> selection for some future possibility. In this case
> you suggest that junk DNA has to be kept around
> because it might become useful in the future. How
> does an individual know that it needs to store excess
> DNA in its genome because theres' a small chance that
> one of its descendants might find a use for it at
> some time in the far distant future?

Wrong. What Tim's suggesting is standard natural
selection. Think about it. At any point in time there
are millions of populations in existence. These
populations are in constant competition with each other
for finite resources. As Tim (and Jeff) suggest,
populations that have the ability to quickly assume
'new' adaptations will have a selective advantage over
those that cannot or that cannot as quickly achieve such.

> Note that the genomes of bacteria appear to be
> under selection for small size so they can replicate
> quickly. That's why they don't have very much junk
> DNA. If your speculation is correct then there should
> have been much less gene duplication and divergence in
> bacterial lineages. Does the data lend support to your
> speculation?

I'm not following.

> > Some references to theories of the "function" of "junk" DNA:
> >
> > "Inserting introns improves genetic algorithm success rate:
> > Taking a cue from biology"
> >
> > - http://citeseer.nj.nec.com/context/17647/246003
>
> This seems to be mostly computer scientists discussing
> biology. I didn't see anything there that's worth
> remembering. Perhaps you could summarize their very best
> argument for the selective advantage of excess genomic
> DNA?

Survival of the fittest.

> Please don't use the success of a genetic algorithm
> as biological evidence.

Do you have a rational basis for your bias against genetic algorithms?
Jim

Relevant Pages

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