the liver and the brain

Wolf Kirchmeir wwolfkir at sympatico.ca
Sun Sep 5 20:05:51 EST 2004


r norman wrote:

> On Sun, 5 Sep 2004 23:47:08 +0100, David Longley
> <David at longley.demon.co.uk> wrote:
> 
> 
>>In article <8d8494cf.0409051127.32b66d14 at posting.google.com>, dan 
>>michaels <feedbackdroids at yahoo.com> writes
>>
>>>This N.v.N thing is obviously a spectrum, with a lot of animals down
>>>on the nature/instinct end, and a general trend towards greater
>>>importance of nurture on the other end. If you look at it this way, it
>>>seems a waste of time to argue absolutes of "nature vs nurture",
>>>rather it seems more fruitful to figure out about where on the
>>>spectrum various animals would lie. In addition, you probably need
>>>several such spectrums, or scales, in order to cover different
>>>attributes ... motor, perceptual, etc ... as there is no doubt some
>>>differential placement regards each.
>>>
>>>Back to perception, it's actually not too hard to hypothesize the
>>>existence of neural circuitry for distinquishing predators from prey
>>>[or self-same species]. Frogs already have the basis of this in their
>>>class 3 and 4 retinal cells. One imagines precocial animals rely on
>>>something similar, albeit more sophisticated.
>>
>>If anyone is sincerely interested in learning how to approach these 
>>(highly sensitive & 'political') issues within science, they'd be wise 
>>to do a search on "behavioural genetics". Although we're soon likely to 
>>see interval or ratio measures of behaviour replacing the classical 
>>ordinal measures (upon which the factors comprising "intelligence" ('g') 
>>were classically derived using IQ tests), the current and future focus 
>>is likely to be on extensional measures such as chromosome 6 genes and 
>>how these may relate to individual differences in parameters of 
>>behaviour related to 'g' but measured at the interval or ratio levels of 
>>measurement (cf. RT or IT at the msec level etc).
>>
>>Anyone interested should have a look at 
>>http://www.robertplomin.com/index.html and related links, paying 
>>attention to what people like Jensen have had to say over the years. 
>>After a little Herrnstein along the way, it may become clearer why the 
>>priority of behaviour analysis has been emphasised so much in c.a.p, and 
>>why the indeterminacies so characteristic of what's done at the other 
>>end of the measurement scale (so favoured by mentalists) has been 
>>denigrated as no more than muddled folk psychological rhetoric.
> 
> 
> The history of human behavioral genetics and sociobiology ala Jensen
> and Herrnstein is a sorry story filled with abuse of scientific
> notions for very partisan political objectives.  Racism, or at least
> racial overtones, hangs heavy over the topic. No doubt some of the
> newsgroups involved in this exchange, like comp.ai.philosophy, have
> had rather extensive discussions of these issues
> 
> However, from  my perspective as a biologist on bionet.neuroscience,
> there is a valid scientific study of the natural behavior of a wide
> variety of animals living in their natural environment, a field
> usually termed ethology.  The role of genetic "predetermination" in
> structuring the nervous system as a whole, in producing specific cells
> and circuits between cells, and in producing behavior is established
> for many animals beyond any question.  In the roundworm,
> Caenorhabditis elegans, for example, every cell division from the
> fertilized egg is absolutely determined so that every adult individual
> of that species, barring mutation, has exactly the same number of
> cells (959 to be specific, with 300 neurons and 81 muscle cells).
> Humans, of course,  show a different course of development.  Still,
> understanding just how genetic and environmental aspects interact in
> producing mammalian nervous systems is something that is actively
> being investigated.  I agree that many popular accounts of
> "evolutionary psychology" seem rather strained, to say the least.
> Still, genes undeniably have a strong impact on cells.
>

Yes, I just love C. elegans. Especially the fact that it needs 300 
neurons but only 81 muscle cells. Lovely! Brain over brawn very time, 
eh? :-)

Question: Are there any environmental factors whose presence or absence 
disrupt or divert development? Any non-lethal ones? Are there any 
environmental factors whose presence/absence affects the timing of 
development? I suspect there are, but I would like to know one way or 
the other. I'm not asking about the obvious ones, such as water, without 
which the creature will die. Anther way of asking the question is, 
What's the range of, e.g., pH, etc in a normal environment for this 
worm? Any differences at either extreme? Etc.



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