Re: Evolution of sleep
- From: Darwin123 <drosen0000@xxxxxxxxx>
- Date: Fri, 22 May 2009 01:59:56 -0400 (EDT)
On May 21, 12:17 pm, "Tom Hendricks / Musea" <tom-hendri...@xxxxxxx>
wrote:
A complete shutdown isn't needed for digestion. If a shut down=A0 =A0I agree as far as mammalian sleep. However, the development of
sleep probably took many small steps. I suggest that dormancy in fish
would be most likely to be the first step toward developing "sleep." I
think it is obvious that dormancy would most probably develop in fish
for the purpose of avoiding predators.
But that doesn't make sense. Why would dormancy not be just slowing
down or not moving. Why the complete shut down that comes with sleep?
was needed for digestion, then a shut down would always come at a
fixed number of hours after eating. White sharks, tuna and mackeral
never go dormant. Yet, they eat and digest food.
Mammalian sleep doesn't always come with a complete shut down.
Dolphins have this system where half their brains are asleep, never
the whole brain. They can thus get the benefits of sleep for their
entire brain, one half at a time. However, their bodies don't go
dormant at any time. They have to keep swimming to stay alive. If they
are knocked out, so both sides of the brain are dormant, they stop
breathing.
Of course, sleep isn't always associaed with dormancy even in
human beings. Some people sleep walk. Studies show that soldiers can
sometimes keep marching even when they sleep. Sleep is usually
associated with a shut down, but not completely.
That would make them totally vulnerable.A shut down makes them undetectable, not vulnerable. The shut
down usually occurs at night, when there is no light. Thus, an animal
hunting for them would have to use sound or some type of chemical
sense to find them.
If the animal doesn't move move, it doesn't don't make a sound.
Furthermore, if they don't move, they don't leave a chemical trail. An
odorant spreads much slower if the anial doesn't move. If the animal
moves, they leave this long trainl on the ground. In water, the
turbulence generated by their motion spreads the odorant. So an animal
that is shut down at night is very difficult to detect.
A camouflaged animal is much easier to see if it is on the move.
Many animals have motion detection responses. They can see things that
move easier than things that don't move. A camouflaged animal is
almost impossible to see when it is standing still. It becomes very
easy to see when it moves. Therefore, nocturnal animals would also
find it better to shut down during the day.
An animal standing still isn't much more vulnerable than an animal
moving. It can always start moving when attacked. However, an animal
standing still is much harder to find.
Please watch that movie, Das Boot (the Boat) The submarine is
trying to hide from the battleships on the surface. The submarine has
just sunk a merchant ship. The enemy battleships are now hunting for
the submarine. The submarine commander stops the engines and tells
everybody to shut up. They even turn off the lights, so the electric
generators can be turned off. This way, the enemy battleships won't
hear them.
By your logic, the submarine is more vulnerable when the
generators are turned off. The submarine commander should order full
speed ahead, so they will be ready to fight back against the
battleship. However, why should he? He sunk the merchant ship. Now, he
wants to stay alive until he is ready to hunt the next merchant ship.
No sleep is part ofGosh, you are certainly sure about it! You just keep repeating
digestion, and it's time to investigate what the alimentary tract is
doing during sleep.
that sleep is part of digestion, and never provide any studies linking
the two.
Please provide evidence that people digest food better when they
sleep. That seems to be your most deep seated belief. Personally, I
find it hard to believe that a complete shut down is necessary for
digestion. The example of the dolphin is really revealing. Here you
have sleep ( half a brain at a time) and no shut down for the body.
Five questions that need answer before further discussion:
1) What is your explanation for dolphins needing sleep, one hemisphere
at a time, with no cessation in swimming?
2) What is your explanation for the fact that both tuna and white
sharks swim constantly, with no shut down, even after they eat?
3) Why would a vampire bat, which has a continuous liquid diet, need
to sleep in caves during the day?
4) Why do starving animals, including starving humans, need sleep when
they have nothing to digest?
5) When were you first certain that sleep is mostly for digestion?
.
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