Re: twins

On Thu, 15 Mar 2007 09:00:51 -0600, Dick <remdickhm@xxxxxxxxxxxxx>
wrote:

On Wed, 14 Mar 2007 22:57:32 -0400, r norman <r_s_norman@xxxxxxxxxxxx>
wrote:

On Wed, 14 Mar 2007 22:30:25 -0400, "Darkwing"
<theducksmailATyahoo.com@xxxxxxxxxxxx> wrote:


"Dale Kelly" <dale.kelly@xxxxxxxxxxx> wrote in message
news:tLCdnWWt6u8vNmXYnZ2dnUVZ_rjinZ2d@xxxxxxxxxxxxxx
how is saying that our fate is determined by biology any less illogical
than saying our fate is determined by the will of Gods? if you believe in
free will, then there can be NO predetermination, as each decision trumps
the previous decision

if twins have the same DNA and same bodies, then why don't they have the
same mind and will and become the same person?

this is proof that the mind and will and conscious are not biological



Of course they are biological, they definitely aren't magical. Just because
twins share the same DNA hardly mean the random mutations caused by copy
errors and high energy particles are identical as well. I know quite a few
twins, they are still not "identical", they always look somewhat different
and the longer they live the less identical they look.

Now if you want to discuss why old married couples look like each other more
as they age then you do have a real mystery on your hands!

You don't have to invoke mutations to get differences between
identical twins. There is enough variability in the developmental
process to produce significant difference. The fingerprints, for
example, depend on tiny positional factors which are easily modified
by brownian movement so that identical twins do not have the same
fingerprints. Other alterations, especially in the fine details of
just how neuronal synapses occur, are equally sensitive to these
external 'random' events. There are people who argue that quantum
mechanical uncertainty also plays a role in the function especially of
subcellular organelles which introduces even more irregularities in
function. Even without that, there is enough environmental influence
to produce significant differences.


What is the explanation for those unique fingerprints and their
stability over a lifetime?

I was afraid somebody might ask for details. It is sort of
complicated. The dermal ridges that determine the dermatoglyphic
pattern (the technical term for the fingerprint) form early in
embryonic development, in the 11th week of gestation. Galton, in
1892, first demonstrated that the pattern does not change throughout
post embryonic life. It is based on the pattern of cell proliferation
in the volar pads of the embryo. Although there are general patterns
that are genetically determined, with some patterns indicating
developmental or genetic defects, the fine details depend on fine
circumstances occurring in the early embryo .

Probably the best source is W. Babler who has summarized much of his
work at http://www.clpex.com/Information/Babler/BablerArticles.htm.
The notion that epigenetic factors determine the pattern was first
ascribed to Cummins, 1926. (Cummins , H. 1926 Epidermal-ridge
configurations in developmental defects, with particular reference t o
the ontogenetic factors which condition ridge direction. Am. J, Anat.,
38.89-151.

Note, I somewhat overemphasized the difference between fingerprints in
identical twins -- they really are quite similar. The point I was
making is that there are enough differences to distinguish them. And,
if you ascribe similar very small differences to neural circuits, you
could produce rather striking behavioral differences. If when
genetics "predetermines" an overall pattern, sufficient very fine
differences make for non-determinism in the overall product.




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