From a system standpoint it makes sense that the genome would accumulate a lot of junk. Simple natural selection preserves [currently] essential components of the genome; errors and omissions would mostly negatively impact the probability of survival of progeny. Since errors and omissions are unavoidable given limited resources, some level of functional redundancy is preserved as well. This redundancy may include both duplicate pieces of genome as well as pieces that code alternative methods for producing the same function. But the ability to adapt to inevitably changing conditions over time is essential to preserving a genomic lineage, and so the reproduction mechanism needs to produce "errors" and duplicates at some frequency, and to preserve the resulting "junk" (which it doesn't really know is junk). In the absence of the "junk" turning into nonjunk, by acquiring some role, whether positive or negative, evolution will just carry the junk along and continue to mutate it. Only if the junk interferes with the nonjunk, or when the burden of carrying all that extra DNA is sufficiently large, will natural selection tend to eliminate it. A sufficiently intelligent life form, if one ever evolves, might eliminate the need for this genomic-based adaptation mechanism. --ms On 07-Sep-12 11:50, Jeffrey Shallit wrote:
Well, I don't agree at all. There are *good reasons* to believe that much of the genome is junk (see, for example, the experiments referred to on Larry Moran's blog) and it is completely reasonable to deduce this from what is currently known. Could the junk proponents be wrong? Of course - all science is provisional. Nevertheless, that is what the evidence currently says.
I strongly recommend reading blogs written by actual biologists who have studied the area for years. Another good one is Genomicron, written by U. Guelph biologist T. Ryan Gregory:
http://www.genomicron.evolverzone.com/category/junk-dna/
On 9/7/12 11:03 AM, Dan Asimov wrote:
With suspecting, there's nothing to forgive.
With acting certain -- when we just don't know -- and announcing it to the world, that's not so forgivable.
--Dan
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