IUBio

the liver and the brain

r norman rsn_ at _comcast.net
Thu Sep 2 17:04:43 EST 2004


On 2 Sep 2004 13:56:56 -0700, feedbackdroids at yahoo.com (dan michaels)
wrote:

>r norman <rsn_ at _comcast.net> wrote in message news:<ge1dj0111j3l0cssuovuaqhhu7cvh092h1 at 4ax.com>...
>> On 1 Sep 2004 18:58:10 -0700, feedbackdroids at yahoo.com (dan michaels)
>> wrote:
>> 
>> >r norman <rsn_ at _comcast.net> wrote in message news:<p81cj0dpssidqvd146ckens4c5hss9t0tb at 4ax.com>...
>> >
>> >> 
>> >> The evidence is quite clear.  There is good, hard experimental data to
>> >> prove that genetically determined motor pattern generating circuits do
>> >> exist in mammals in general and humans in particular.  There is also
>> >> good, hard experimental data to prove that experience and synaptic
>> >> modification is usually necessary to make these circuits function
>> >> appropriately to produce useful, responsive, and adaptive behavior in
>> >> the functioning organism.
>> >> 
>> >
>> >
>> >Thanks for all the references. It'll take a while to get through them.
>> >Your summary doesn't help much, however, as it doesn't distinquish
>> >between ungulates which run within minutes of being born as compared
>> >to humans which take a year or so to make it to pokey walking. Off to
>> >the abstracts.
>> 
>> Not those particular two, a  rather unusual contrast.  However 
>> Lossi et al has something close enough, saying: "In this study we have
>> investigated the histogenesis of the cerebellar cortex in guinea pig
>> (a precocial species) and rabbit (an altricial species) at different
>> stages of pregnancy and postnatal life."
>> 
>> I believe the key words you need are altricial and precocial which
>> describes exactly the difference you mention,  not ungulate and human.
>
>
>In answer to both of your replies, I specifically picked ungulates
>because they *are* so much more advanced than humans AT BIRTH. It
>takes human babies a year or so before their brains are wired up enuf
>to both walk and to see. IE, babies apparently have to "learn to see"
>- which to a large extent involves making connections between the
>properties of objects regards both modalities - vision and touch.
>Human babies don't appear born already able to distinquish a general
>object from a general background - although there is some evidence
>they do respond to faces, smiles, etc, to some extent. As you
>mentioned, these things take practice. As Piaget studied, human
>sensorimotor response develops in stages over the course of the 1st
>year.
>
>In contrast, since ungulates pop out into the world being able to walk
>and run within hours, I was also wondering that their visual systems
>might also be similarly advanced, as compard to humans and other
>animals like you mentioned. Do they have to "learn" what a lion looks,
>or might their visual systems already have some hard-coding regards
>this?

I do understand exactly the distinction you are making.  It is exactly
the distinction between precocial and altricial.  People involved in
studying animal behavior, developmental biology, ecology and
evolution, and physiology have known about these differences and
described them at length.  There is extensive literature about these
differences, especially for birds. Partridges, pheasants, and quail
(Megapodidae) hatch fully feathered and capable of flight.  They
receive no parental care and are fully independent from the time of
hatching.  On the other hand, songbirds and parrots are almost
embryolike at the time of hatching and require extensive parental care
and feeding.  

All I am trying to suggest to you is that if you want to study the
differences, especially differences in the nervous system that
underlies the differences in behavioral abilities, then ungulates and
humans are not a very good choice of subjects.  There are much better
choices.  For example, guinea pigs are precocial while most mice and
rats are altricial.  This makes for a much better comparison since the
species, being in the same order,  are more closely related
evolutionarily.  They are also more similar morphologically and
ecologically than, say, humans and ungulates. 

Incidentally, humans and most primates are really not particularly
altricial and, in some studies, are even classed in the precocial side
of the spectrum.  Human infants are born with open eyes, hair, sexual
dimorphism, ability to vocalize, and many other characters that are
associated with precocial development.  Compare that with rats and
mice, for example, born with closed eyes and no hair and much greater
limitations in movement than most primates or even the marsupials
which are really still embryonic at birth.





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