Received: by alpheratz.cpm.aca.mmu.ac.uk id XAA05756 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-majordomo@mmu.ac.uk); Sun, 4 Feb 2001 23:33:54 GMT Message-Id: <5.0.2.1.0.20010204165450.01ff2a30@pop3.htcomp.net> X-Sender: mmills@pop3.htcomp.net X-Mailer: QUALCOMM Windows Eudora Version 5.0.2 Date: Sun, 04 Feb 2001 17:21:20 -0600 To: memetics@mmu.ac.uk From: Mark Mills <mmills@htcomp.net> Subject: Re: Evolution of ontogeny In-Reply-To: <F122qi66Y2QTUf65Y5Q0000ed30@hotmail.com> Content-Type: text/plain; charset="us-ascii"; format=flowed Sender: fmb-majordomo@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
Scott,
At 03:44 PM 2/4/01 -0500, you wrote:
>The late 19th century incarnations of the relationship between ontogeny
>and phylogeny were usually influenced by the German Darwinian hyperzealot
>Ernst Haeckel and his slogan that "ontogeny recapitulates phylogeny" which
>in a nutshell means that in their development organisms literally proceed
>through stages pretty close to their adult ancestors. One could think of
>humans starting a protozoans then becoming spongelike or worm-like then
>somewhere along the line becoming fish-like and so on until reaching
>human-hood. Related to Haeckel's notion paralleling ontogeny and phylogeny
>is a causal statement that phylogeny causes ontogeny.
Interesting recap.
>I think it was Walter Garstang who was noted for turning Haeckel's dictum
>on its ear and saying the opposite that ontogeny causes phylogeny or that
>ontogeny creates phylogeny. Garstang was interested in phenomena that
>didn't reek of recapitulation (ie- neoteny and paedomorphosis).
Sounds like chicken and egg problem on a grand scale.
John Wilkins has a paper under-development that argues functionality is
misplaced in biology unless one makes explicit the model one is using (with
ranges of applicability). Though you didn't mention function, the term
'causation' only makes sense if there are functions. To broadly state 'x'
is a function of 'y' in the evolutionary scheme without defining the model
leaves one prone to various logical problems.
>One could confine a definition of evolution to organisms that develop
>(ie-exhibit an ontogeny-metazoans and possibly metaphytes) by saying that
>evolution is based on heritable changes in development, which isn't too
>far from what you're talking about above. This would be indirectly related
>to evolution's definition of being changes in allelic frequencies within a
>gene pool or population. I have tended to prefer an epigenetic view
>myself, not quite one of those "beads on a string" or "bean bag genetics"
>thingies.
By heritable, do you mean 'on the DNA'?
I'm not very familiar with epigenetic. I looked it up and found two
references:
http://www.olemiss.edu/courses/psy529/Lectures/Lecture1/class1.htm
On the theoretical side, I don't have as much to flesh out the original
definition. How we come to be who we are is the premier theoretical
question to be answered. Explanations generally are in terms of nature or
nurture, maturation or experience, or some combination of these. If
children begin to avoid a visual cliff around six months of age, the
question is whether this is a native capacity that emerges with maturation
or whether it is founded on sensory-motor experience in the world. A major
emphasis in this course will be developing an integrative model that allows
us to offer an explanation of phenomena such as this without having to
choose between nature, nurture, maturation, or experience. I'll refer to
it as the epigenetic model.
http://biotech.icmb.utexas.edu/pages/dictionary.html
1. epigenetic
Definition: Describes something which influences the behavior of a
cell without directly affecting its DNA or other genetic machinery, such as
an environmental effect.
2.epigenetic changes
Definition: Any changes in an organism brought about by alterations
in the action of genes are called epigenetic changes. Epigenetic
transformation refers to those processes which cause normal cells to become
tumor cells without the occurrence of any mutations.
Do these describe the sense of epigenetic you are using?
mark
http://www.htcomp.net/markmills
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