Just like in our DNA...

[Charles G Waldman]

Fredrik Lundh writes:
 > 
 >     2. since there's no possible chance that an
 >     evolutionary process would leave junk in
 >     there, Darwin was obviously wrong.

I realize that this posting is in jest, but I can't help replying to
it anyhow, to make the observation that if the DNA sequences in
question are never translated into proteins, then there is simply no
pressure of natural selection acting either for or against the
propagation of these sequences; that is, since they represent neither
an advantage or a disadvantage to their host organism, the most likely
outcome is that they simply continue to be propagated, mostly
unchanged.  Again, the analogy with code is relevant: if there is a
section of your program that is never called, it doesn't matter if the
code therein is good or completely bug-ridden; if your only criterion
for gauging the quality of programs is their runtime behavior, rather
than a critical examination of the source-code, there will simply
never be any reason to excise the unused portions.  It seems to me
(but I am not a biologist!) that it would be extremely unlikely, that
without a "Divine Planner", DNA strands would evolve in a way so as to
be devoid of "Junk" sections.... that's just asking too much, to ask
not just for a molecule that "does the job" of carrying the genetic
information, but that does it with 100% efficiency.  There's not
sufficient selective pressure for the DNA to be forced to be efficient
(as opposed to, for example, the sunlight-collecting efficiency of a
leaf, where efficiency matters).  The code-bases are small, molecules
are cheap, and there's plenty of room for some extra unused bits in
there.

Of course, that's (supposed to be) the difference between Evolution
and Engineering; in Natural Selection, only runtime behavior matters,
but in our field, there's (supposed to be) an omniscient designer
critically examining the code.  But, given some of the code I've seen
over the years, I start to wonder sometimes...