From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Sat Nov 30 2002 - 09:09:58 MST
On Fri, 29 Nov 2002, Ramez Naam, responding to me wrote:
> Unless, of course, those regenerative abilities you mention required a
> great deal of infrastructure that is laid down during lizard or
> lobster development. (I honestly don't know.)
I believe these traits evolved adaptively as defense mechanisms.
I'm moderately sure they are due to a maintenance of totipotent
stem cells. In lizards I believe the neurons grow out first
then the muscles and skin later grow around them.
> In humans, morphology and cognitive architecture are laid down during
> early development, both as an embryo and in critical years after being
> born. We simply don't grow new limbs or new brain regions
> spontaneously after a certain age as embryos.
Actually the liver can regenerate large sections of itself and it looks
like we have stem cells active in some brain regions. And young
children have a limited ability to regrow lost limbs, e.g. fingers.
> Let's say you wanted to make an adult human grow a new mental capacity
> - the ability for 4D visualization, say, or a new mental organ that
> could do fast mathematical calculation.
Well, now you are talking some really extensive engineering. It might
be a lot easier to simply build this in real hardware and then develop
an interconnect. The interconnects (with dozens of I/O lines) are
being done now.
> These are good examples. But again I have to ask: is there
> significant infrastructure for these transformations already laid
> during the developmental process of the earlier phase? Once again I
> plead ignorance, though I have my suspicions.
Because you can induce cellular apoptosis under genetic control
(C. elegans for example removes some very specific cells as it develops)
and you can regrow limbs or organs under genetic control (see previously
cited examples) I don't see very significant problems so long as
you aren't attempting something very radical for which there isn't
an example in existing genomic capabilities.
Robert
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