Don't implicitly assume that all codons in DNA were at some time useful. It appears that many, such as introns and repeated sequences and viral fragments are just free-riders on the replication machinery. It's as you would expect from a random mutation process, that a lot of junk with no selection pressure against it could accumulate. Something like 80% of human DNA is active, in the sense that it codes for some other molecule. But those other molecules are not necessarily functional. http://gbe.oxfordjournals.org/content/early/2013/02/20/gbe.evt028.full.pdf+h... How much of human DNA is actually functional for the organism is controversial, but comparison with what has been conserved by evolution in related species suggests that only around 15% is. Brent “The onion test is a simple reality check for anyone who thinks they can assign a function to every nucleotide in the human genome. Whatever your proposed functions are, ask yourself this question: Why does an onion need a genome that is about five times larger than ours?” --—T. Ryan Gregory On 5/13/2016 3:52 PM, Dan Asimov wrote:
What Henry says makes perfect sense, since the conditions under which some old DNA were good for might very well return at some point.
Maybe this helps explain how surprised I often am when an organism seems to mutate into a better-adapted one in a ridiculously short time. The random mutation theory just doesn't seem to explain this, if you ask me.
—Dan
On May 13, 2016, at 8:38 AM, Henry Baker <hbaker1@pipeline.com> wrote:
Yes. Code that is "commented out" is still left in for documentation and to provide a fall-back should conditions change which require going back to a previous method.
I suspect that the same thing is going on in the genome, where evolution plays with alternatives, but keeps the older deprecated and disabled versions around (either in this particular individual, or in the pool of genes in the entire population) as fall-backs.
At 03:29 PM 5/12/2016, Brent Meeker wrote:
On 5/12/2016 11:44 AM, Henry Baker wrote:
We've been running this evolutionary experiment with Unix/Linux/OpenWRT/... for the past 50 years, and the outcome is clear: it is nearly impossible to come up with a mechanism that enforces small DNA/RNA/kernel size.
Or to flip this around, the marginal cost of adding additional "functionality" -- especially functionality that is executed only occasionally (i.e., small *dynamic* cost) -- is almost free. Which also means that non-functional code is also almost free and may persist indefinitely. And some code may even go from non-functional to functional and vice versa, depending on mutations.
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