Seems to me that if we are going to get scientific about this that we
will have to speak about migrating animals who are born in one area
and then somehow have an inborn ability to migrate 1000 miles away to
a place that they have never seen.
Sounds like magic to me or just plain old hoohey if it wasn't so true....
Why would homo sapiens be completely exempt from these sorts of things?
My two cents,
Nisha
--- In letterbox-usa@yahoogroups.com, "mr_elsworth_toohey"
wrote:
> "Iron in their nose"? Where in the world did you get that? Just to
> make sure I Googled it and could find nothing remotely like that.
> Certainly doesn't explain the ability of people to navigate a virtual
> environment. Most theories of human navigational abilities posit that
> it is based on cognitive mechanisms and spatial cognition.
> (Remembering landmarks, using geographic cues, the cognitive ability
> to manipulate perspectives and spatial quantity and an innate
> Euclidean concept of space) A Euclidean sense of space is one of
> three-dimensional positions. The human life-world is certainly
> organized in this way, and we and other primates clearly perceive
> dimensional space, it is our human ability to employ cognitive
> mechanisms that understand space in this way that can be used to
> organize action. Such a mechanism, or mechanisms, underpin our most
> sophisticated everyday navigational and mapping skills.
>
> Gender differences are most likely due to women accepting the popular
> notion that they lack a "sense of direction" and therefore score lower
> on test of their wayfinding abilities.
>
> To the best of my knowledge and from a quick internet search there are
> no human anatomic structures that aid in navigational ability other
> than those that enable our cognitive abilities.
>
> ET

Evolution my dear, some things we kept, some we lost. Birds use
several mechanisms some of which we retain some of which we don't.
Birds use photoperiodism, the lengthening and shortening of days in
spring and autumn, which affects birds' pituitary and pineal glands.
These glands generate hormones that stimulate birds to become
increasingly restless. Daytime migratory birds use vision to steer by
the sun, aided by a precise sense of time (see photoperiodism). Night
fliers take compass cues from star patterns. While in flight, birds
may use geographic land forms to help them orient direction and
course. The outline of North American coasts, and the north-south
direction of many large rivers and mountain chains, aid in migration.
Many of these we use along with our cognitive ability as previously
mentioned. Homing pigeons and some migratory birds see ultraviolet and
polarized light to assist their migration, an ability which we
lack...birds got it, we didn't. Birds such as sparrows, pigeons,
bobolinks and others can detect magnetic fields; cells in the bird's
brain contain magnetite, an iron oxide crystal that aligns with
magnetic north similar to a compass needle. Evidence suggests that
these cells may serve as receptors that send directional information
to the brain. Human's brains which have been extensively studied lack
these specialized cells as do many other migratory birds that do not
have the ability to use magnetic fields to navigate. Our noses
certainly don't contain these specialized cells. Applying a thorough
knowledge of anatomy, physiology and physics; even if you pureed the
noses of people who scored higher on tests of wayfinding and found
a higher iron content than the people who scored low, how would you
propose that this influences navigational ability? The force of the
earth's magnetic field is 0.00005 tesla (tesla is a measure of
magnetic field strength) where as that of a strong refrigerator magnet
is 0.1 tesla so the earth's pull on your "ironic" nose, even if your
nose were solid iron, wouldn't come close to generating enough force
to register in any of the proprioceptors in your neck (proprioceptors
are the nerve endings in joints that tell you the pressure on joint
cartilage, this information is coordinated with the anatomic position
of the joint and processed along with information on the tension on
muscles and tendons to give you the ability to know the position of
your body or in this case your head even with your eyes closed as well
as a sense of the vector of external forces acting on your head.)
Remember we lack the cells with the specialized intracellular
structure to give us information on the position of iron oxide
crystals with in the cell. Sensory input to the brain from the nose is
mediated through the Trigeminal nerve. Trigeminal nerve disorders are
well documented and studied and a quick Google search yielded no
indication that people who have damaged Trigeminal nerves loose their
sense of direction.

Humans have a significant ability to adapt to different climates and
don't have a need to migrate and therefore did not evolve any
specialized tissues or structures to aid in this, birds and other
animals do and have evolved various mechanisms which we lack. We still
must rely our cognitive abilities for navigation.

Anyone know how the monarch butterflies do it? This insect is born
1000+ miles away and then finds it way home to places like Mexico to
overwinter before returning to the States to lay it's eggs and then
the cycle starts all over again.
It did used to be scientific fact that this was impossible....
My three cents,
Nisha
--- In letterbox-usa@yahoogroups.com, "mr_elsworth_toohey"
wrote:
> Evolution my dear, some things we kept, some we lost. Birds use
> several mechanisms some of which we retain some of which we don't.
> Birds use photoperiodism, the lengthening and shortening of days in
> spring and autumn, which affects birds' pituitary and pineal glands.
> These glands generate hormones that stimulate birds to become
> increasingly restless. Daytime migratory birds use vision to steer by
> the sun, aided by a precise sense of time (see photoperiodism). Night
> fliers take compass cues from star patterns. While in flight, birds
> may use geographic land forms to help them orient direction and
> course. The outline of North American coasts, and the north-south
> direction of many large rivers and mountain chains, aid in migration.
> Many of these we use along with our cognitive ability as previously
> mentioned. Homing pigeons and some migratory birds see ultraviolet and
> polarized light to assist their migration, an ability which we
> lack...birds got it, we didn't. Birds such as sparrows, pigeons,
> bobolinks and others can detect magnetic fields; cells in the bird's
> brain contain magnetite, an iron oxide crystal that aligns with
> magnetic north similar to a compass needle. Evidence suggests that
> these cells may serve as receptors that send directional information
> to the brain. Human's brains which have been extensively studied lack
> these specialized cells as do many other migratory birds that do not
> have the ability to use magnetic fields to navigate. Our noses
> certainly don't contain these specialized cells. Applying a thorough
> knowledge of anatomy, physiology and physics; even if you pureed the
> noses of people who scored higher on tests of wayfinding and found
> a higher iron content than the people who scored low, how would you
> propose that this influences navigational ability? The force of the
> earth's magnetic field is 0.00005 tesla (tesla is a measure of
> magnetic field strength) where as that of a strong refrigerator magnet
> is 0.1 tesla so the earth's pull on your "ironic" nose, even if your
> nose were solid iron, wouldn't come close to generating enough force
> to register in any of the proprioceptors in your neck (proprioceptors
> are the nerve endings in joints that tell you the pressure on joint
> cartilage, this information is coordinated with the anatomic position
> of the joint and processed along with information on the tension on
> muscles and tendons to give you the ability to know the position of
> your body or in this case your head even with your eyes closed as well
> as a sense of the vector of external forces acting on your head.)
> Remember we lack the cells with the specialized intracellular
> structure to give us information on the position of iron oxide
> crystals with in the cell. Sensory input to the brain from the nose is
> mediated through the Trigeminal nerve. Trigeminal nerve disorders are
> well documented and studied and a quick Google search yielded no
> indication that people who have damaged Trigeminal nerves loose their
> sense of direction.
>
> Humans have a significant ability to adapt to different climates and
> don't have a need to migrate and therefore did not evolve any
> specialized tissues or structures to aid in this, birds and other
> animals do and have evolved various mechanisms which we lack. We still
> must rely our cognitive abilities for navigation.

--- In letterbox-usa@yahoogroups.com, "marthastewartletterboxer"
wrote:
> Anyone know how the monarch butterflies do it? This insect is born
> 1000+ miles away and then finds it way home to places like Mexico to
> overwinter before returning to the States to lay it's eggs and then
> the cycle starts all over again.
> It did used to be scientific fact that this was impossible....


If it was occouring how could it simultaneously be impossible?

Anyhow. Scientists theorize that monarchs have two systems that aid
them in their migration. One is the ability to use the sun as a
compass. In scientific studies, monarchs tricked with artificial
lights into believing that the time is off just by a few hours will
alter the direction of their flight upon release, according to where
the sun "should" be.

Yet many scientists believe that, since monarchs can travel 90 miles
or more in a day, they must be able to fly at night, without the
benefit of the sun to orient them. Hence they believe that monarchs
also fly by following magnetic fields. The diet of monarch larvae is
almost exclusively milkweed plant, from which the caterpillars
biosynthesize magnetite (see previous post).

Sorry, Her Ladyship forgot to mention that you can read that info and
more about Monarch Migration at:
http://www.mexconnect.com/mex_/butterflyhistory.html

Geez, I love a good, scientific response.

I spent an enjoyable few minutes getting a great deal out of every little aspect you took into consideration. I just wanted to let you know I enjoyed the heck out of that.

: )

tabulator32


On Friday, August 05, 2005, at 12:36PM, mr_elsworth_toohey wrote:

>
><>


[Non-text portions of this message have been removed]

It is more likely that our evolution given ability to shop mitigated
the need evolve the specialized tissues than any ability to adapt to
climates. I've inserted the shopping gene into a homing pigeon in my
lab. The pigeon keeps picking out a really nice compass at REI but is
bewildered as to how to hold it. Back to the lab....

--- In letterbox-usa@yahoogroups.com, "mr_elsworth_toohey" >
> Humans have a significant ability to adapt to different climates and
> don't have a need to migrate and therefore did not evolve any
> specialized tissues or structures to aid in this, birds and other
> animals do and have evolved various mechanisms which we lack. We
still
> must rely our cognitive abilities for navigation.