On Sat, 8 Dec 2001, Mike Lorrey wrote:
> Is this really true, though? From the stuff I've been reading, animals'
> genes are pack-ratty about saving information from ancestors. For
> example, given the right GE signals, it should be possible to make a
> human grow an insect wing on any part of their body, since we still have
> those genes in a dormant state.
Actually, insects are probably a poor example since they branched off
from the vertebrate tree so early. Its safe to say that we probably
have most of the genes involved in aspects of vertebrate development
(perhaps for tails for example). But any gene sequences for a form
contained within a unique branch of the tree (e.g. tusk formation)
is unlikely to be present in other species.
> I don't doubt that there are losses,
> that unused information is eventually written over just as de-named
> files on my hard drive are eventually written over, making them
> impossible to undelete at some point in time, but at what rate does this
> happen?
As often as species go extinct (or evolve significantly). I was
primarily focused on all the unique adaptations that get lost
when this happens. The entire natural selection process is
ruthless. For example genes for larger size will generally
get selected for until you hit the carrying capacity of the
environment. Then genes for smaller size will get selected
every year you have a drought or some other food resource
depleting event. Perhaps the entire reason that two chromosomes
pairs were chosen as carriers to allow Nature to do some
"memory" of workable strategies. E.g. If your population
has two size alleles, B and b, then your population will
generally consist of bb Bb bB BB. BB's have the advantage
during times of plenty and bb's in times of famine. Much
of the rest of the time the Bb's simply serve as the
reservoir to carry the different alleles allowing the
population to survive famines and fluorish in times
of plenty.
But you can easily see how it might be advantageous to design
more chromosomes (redundancy) and greater numbers of alleles
into a population so it has more flexibility. Nature developed
a system that is "good enough" but nowhere near the limits.
Robert
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