From: Robert J. Bradbury (bradbury@www.aeiveos.com)
Date: Thu Sep 02 1999 - 15:00:52 MDT
On Thu, 2 Sep 1999, Philip Witham wrote:
>
> This is amazing. How could it be that nature didn't select for this?
> So simple, so apparently effective,
>From the paper:
> the total number of NR2B-containing NMDA receptors per single synapse
> is also increased in transgenic neurons at this stage.
Sorry, but it isn't "simple" to for nature to increase the expression of
a receptor in some part of the brain.
That requires very accurate gene duplication of the gene in
question (without duplicating any negative genes), or a very
specific mutation in the NMDA expression or transcription
regulatory region(s).
> there must be a down side, like - the brilliant mouse decides that
> having children would pinch her lifestyle.
Doesn't have to be a down side. Could simply be that nature is
working blindfolded with its hands tied behind its back.
Mice only have to have a learning rate and sufficient memory to
be able to survive and reproduce. Since their longevity is short
(due to a high hazard function), the selective advantages of improving
these mental traits may be diminished compared with a species with a longer
lifespan. The selection pressure on mice is to find food and
reproduce fast. Whether learning & memory (from a "human" perspective)
enhances this is an open question. I would agree that you could
make a case that enhanced memory could facilitate finding food
and mates. But I'd argue that there are other traits
(such as an enhanced sense of smell or being able to spot birds
in the sky or run quickly) that would enhance its survival
more and therefore have more selection pressure on them.
It would be interesting to look at this gene in squirrels or
other animals whose survival may depend to a greater degree on
their memory.
It is also possible that the mouse genome is at a local optima.
Nature might not be able to do the mutations in the regulatory
regions because this might cause interference with other
regulatory factors. The flexibility of gene regulation isn't
well understood yet and until we know all of the preferred
binding sites (8-12 DNA bases) for the hundreds to thousands
of regulatory factors it is difficult to work this out.
It could be that the specificity of the control elements is
tuned just like a piano and if you have one note thats off the
whole song sounds bad.
However, this article is important because
(a) It shows that learning & memory seem to be "throughput"
related, increase the throughput of the synapses and you
increase your ability to memorize things.
(b) learning/memory can be increased through genetic methods
[that ought to stick in the craw of the Anti-Ag-Bio people,
at least the ones that hate genetic engineering in princple].
(c) it will start the ball rolling on finding more of these genes
which will then lead to germline engineering of children which
will really start the ethics debates rolling -- "The Catholic
Church stands for the right of people to have stupid children.
If God had intended everyone to be smart he would have made us
that way." :-)
Overall, though, IMO, its more likely that nanotech will make this
only marginally relevant. A good part may be that it forces us to
confront the issues before we have the technology to implement them.
Robert
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