[MD] Dawkins a Materialist (is watching?)

[Arlo Bensinger]

[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.