[MD] Dawkins a Materialist (is watching?)

[David M]

Hi Arlo

You're quoting nothing to me that is news, ironic you call
the analogy horrible when your quote uses the
usual 'blueprint' analogy that still falls back to a machine analogy ,
my point was entirely that the machine analogy
is very limited. But all that the talk of communication, community,
and signals quoted below does is simply avoid the issue of
co-ordination because it is assuming the co-ordination is
already built into the DNA, but how is this done? A better
answer is one some researchers are looking at and this is
that a real creature interacting with its environment may be able
to alter the way its children's genes are expressed, and then finally
we might have a feed back mechanism that is plausible rather than
fanciful.

David M

----- Original Message ----- 
From: "Arlo Bensinger" <ajb102 at psu.edu>
To: <moq_discuss at moqtalk.org>
Sent: Thursday, January 18, 2007 3:11 PM
Subject: Re: [MD] Dawkins a Materialist (is watching?)


[Dave M]
The fact that a fertilised egg & a womb, can
generate a potential human being (at what point
do we recognise a human full human being?) is
utterly amazing. The only thing we can compare
this creation to is the way we create machines yet the differences are 
obvious.

[Arlo]
The "differences" are obvious because this is a
horrible analogy. An embryo developing into a
human resembles in no way a human building a machine.

Here is a, lengthy, passage from Steven Johnson's
"Emergence" that deals with this process.

"But cells do more than just follow the dictates
of DNA. They also learn from their neighbors. And
without that local interraction, the master plan
of our genetic code would be utterly useless.

Cells draw selectively upon the blueprint of DNA:
each cell nucleus contains the entire genome for
the organism, but only a tiny segment of that
data is read by each individual cell: muscle
cells read from the lines of code that concern
muscle cells, while blood cells consult the
passages that relate to blood cells. This seems
simple enough, until you ask the question, how
did a muscle cell get to be a muscle cell in the
first place? And that question underlies one of
the most fundamental mysteries of emergence,
which is how complicated organisms, with a wide
variety of building blocks, can develop out of
such simple beginnings. We all start life as a
single-celled organism, and yet by the end of our
development cycle, we're somehow composed of two
hundred variations, all intricately connected to
one another, and all performing stunningly
complex tasks. How does an egg somehow know how to build a chicken?

The answer is not all that different from the
solution that ant colonies rely on. Cells
self-organize into more complicated structures by
learning from their neighbors. Each cell in your
body contains an intricate set of tools for
detecting the state of surrounding cells, and for
communicating to those cells using various
chemical messengers. Where ants used pheromones
to inform each other of their activities, cells
communicate via salts, sugars, amino acids- even
larger molecules such as proteins and nucleic
acids. The messages are partially transmitted
through cell "junctions," small passageways that
admit molecules from one cell's cytoplasm to
another.,This communication plays an essential
role in all cellular activity, but it is
particularly critical for embryonic development
during which a single-celled organism
self-organizes into a mouse or a roundworm or a human being:

We all begin life as a single-celled embryo, but
seconds after conception, the embryo divides
itself into two compartments: a "head" and a
"tail." At that point, the organism has joined
the ranks of multicellular life, being composed
now of two distinct cells. And those two cells-
the head and the tail- have separate instructions
for growth encoded in their DNA: one cell turns
to the "head cell" chapter, the other to the
"tail cell" chapter. At this early stage of
development, the. instructions follow a
predictable pattern: divide into another "head"
and "tail. "Thus, in the second round of
embryonic development, there are four cells: the
head of the head, the tail of the head, the head
of the tail, and the' tail of the tail. Those
four units may not sound like much, but this
cycle of cell division continues at a blistering
clip. A frog embryo self-divides into nearly ten
thousand cells in a matter of hours. The runaway
power of geometric progression is not just a
mathematical oddity-it is also essential to the very origins of life.

Once the embryo reaches a certain size, cell
"collectives" start to form, and here matters get
more complicated. One group of cells may be the
beginning of an arm, while another group may be
the first stirrings of the brain's gray matter.
Each cell has somehow to figure out where it is
in the larger scheme of things-and yet, like the
ants, cells have no way of seeing the whole, and
they have no fixed address stamped upon them when
they come into the world, no factory serial
number. But while cells lack a bird's-eye view of
the organism that contains them, they can make
street-level assessments via the molecular
signals transmitted through the cell junctions.
This is the secret of self-assembly: cell
collectives emerge because each cell looks to its
neighbors for cues about how to behave. Those
cues directly control what biologists call "gene
expression"; they're the cheat sheet that enables
each cell to figure out which segment of DNA to
consult for its instructions. It's a kind of
microscopic herd mentality: a cell looks around
to its neighbors and finds that they're all
working away steadily at creatting an eardrum or
a heart valve, which in turn causes the cell to
start laboring away at the same task.

The key here is that life does not simply reduce
down to transcribing static passages from our
genetic scripture. Cells figure out which
passages to pay attention to by observing signals
from the cells around them: only with that local
interaction can complex "neighborhoods" of cell
types 'come into being. The Nobel laureate Gerald
Edelman calls this· process topobiology, from the
Greek word for "place," topos. Cells rely heavily
on the code of DNA for development, but they also
need a sense of place to do their work. Indeed,
the code is utterly worthless without the cell's
ability to determine its place in the overall
organism, a feat that is accomplished by the
elegant strategy of paying attention to one's
neighbors. As Ridley writes, "The great beauty of
embryo development, the bit that human beings
find so hard to grasp, is that its a totally
decentralized process. Since every cell in the
body carries a complete copy of the genome, no
cell need wait for instructions from authority;
every cell can act on its own information and the
signals it receives from its neighbors." And so
we have come full circle back to Gordon's ants,
and their uncanny ability to generate coordinated
global behavior out of local interactions."

[David M]
But I certainly don't know. So again, do you know?

[Arlo]
Ah, this is going to be one THOSE arguments, eh?
I defer to the Ham/Case thread on Popper,
certainty and the philosophy of science.

moq_discuss mailing list
Listinfo, Unsubscribing etc.
http://lists.moqtalk.org/listinfo.cgi/moq_discuss-moqtalk.org
Archives:
http://lists.moqtalk.org/pipermail/moq_discuss-moqtalk.org/
http://moq.org.uk/pipermail/moq_discuss_archive/