Re: Nonhuman/Nonhumoid body plan Questions

Space Cadet <kaw211@xxxxxxxxx> wrote:
Also I
heard that our body plan is a bad design, like, walking upright is bad
for the lower back, that having the brain at the top, means that
signal from the foot have to travel far and suggest a better place
would be the torso/stomach area, but that would mean increasing the
distance between the nerves for the Eyes & ears!

Our body plan has some problems, but evidently it works well enough to
allow us to conquer the entire planet and quite possibly space. Also,
our body plan isn't a design on its own, it's an adaptation from previous
body plans. The big question when imagining aliens isn't just "what do
they look like?", but "how did they come to look like that?".

One possible disadvantage of having our brain in our stomach could be
temperature. Our brain gets damaged when it's too hot, and our head is
easier to cool than our stomach. And you're probably right that sensor
information from eyes, and ears (not to mention mouth and hands!) is
a bit more important than sensor info from our feet.

Well, I wouldn't
expect them to look exactly like us. But what is so wrong with our
bipedal, bilaterally symetric body plan?

Not a lot. It may not be perfect, but it works well enough, or we
wouldn't be here.

Locomotion:
How many legs would an ET need? On Earth, most life has an even number
of limbs, with high order vertibrate life having usually no more than
4 limbs. 4 legs could be more stable than 2, so an ET could be 4
legged, but a leg, especially for a large, inteligent creature,
requires significant investment of mass in terms of bone and muscle. I
do recall on some science program about robotics that they had shown a
one legged robot, that just hopped around. But I don't think the
design was very stable and in the demo, the leg was constantly moving
to keep the body upright.

The main problem with less legs is balance, which means coordination,
which means brain. A creature with lots of legs can get around with
very few brain cells dedicated to coordinating all sorts of subtle
balance issues. Just move the legs in the right order, and you're
there. We, on the other hand, are constantly shifting our balance.
That requires more coordination, and thus more brain. More brain
probably also means you can get away with having less legs. Chances
are intelligent creatures won't have a lot more legs than we do
(although there are always exceptions).

I know that Niven designed the Pierson's
Puppeteer with three legs and it is a very cool design, that screems
'alienness', but is it really a practical design that would occur in
nature?

How would such a creature evolve? The main reason mammals and reptiles
have 4 limbs is because the fish that crawled out of water had 4 bony
fins. Could a fish with 2 bony fore fins and a bony tail crawl out of
water and have that tail evolve into an articulated leg? Remember, it
doesn't have to be an earthlike fish, just some water animal that has
the required skeletal structure. It might not have our kind of spine.
Would a fish with no spine or a different kind of spine be able to
swim efficiently? Would it make sense for such a fish to develop a
bony tail fin? Or is the Puppeteers' rear leg actually a sort of
spinal tail that developed into something that works like a leg?

Vison:
On Earth, in large animals/mammals, there are two eyes, either placed
in front of the skull(in pretors) or on the sides of the skull(prey).
Could you get away with one eye?

Let's consider the evidence we have. The eye evolved independently
several times on earth. Mammals, birds and reptiles got theirs from
fish, but squids have a completely independently evolved eye that's
nearly identical, and they too have two of them. Insects have very
different eyes, but they also tend to have two eyes. Or clusters of
eyes, perhaps. Spiders, on the other hand, have 4 or 8 or some such
ridiculous number.

In general, two eyes seems very likely. Although I don't doubt that
one eye could be made to work, evolutionary, it's relatively easy
(or likely) to duplicate something you already have compared to
something completely new. If a second eye adds a large benefit (and
it does), it's bound to appear sooner rather than later.

I guess if you mounted it on a long stalk, and rapidly moved it from
side to side while blinking, I guess the brain could generate a 3D
picture from that, but an eye on a stalk sounds like something that
could be easily broken(or bit) off.

Not to mention the fact that moving it around rapidly means coordination
and thus more brain. No problem for higher animals, but for fish and
insects, it could be a problem. Also, moving a non-propulsion apendage
around in water is expensive. And stealthy predators will have to
choose between stealth and depth perception. Lots of problems with
having a single eye.

Going the other route, how about
three eyes? Say have them positioned 120 apart, so that at any given
time and two of the three eyes could form a stereoptic pair.

Exact positioning doesn't matter much. Over the course of evolution,
eyes moved to the top, side or front of the head several times. The
main question is: when it initially appears, does the extra eye add
anything useful? More field of view, better depth perception,
redundancy? I don't see why three eyes would be a problem.

Or lets
go for literal "eyes in the back of the head", Four eyes, each 90
degrees appart, so that any time any two pair of eyes could form a
stereoptic pair, but would a typical organic brain be able to process
that much information from the extra eye(s)?

It can learn to. Our brain can adapt to the weirdest things. I once
heard about an experiment where someone wore glasses that turned his
vision upside down for a long time, and eventually his brain adapted
and he could see and walk around normally. When he took them off
again, everything seemed upside down and he bumped into the furniture
again, until his brain adapted.

Consider the chameleon that can move his eyes around independently.
Our brain would probably have a hard time making sense of that, but
his brain has evolved to make use of it. Two extra eyes won't be a
problem. Even spiders have lots of eyes.

Hand/Arms
Or as they like to say in robotics, the end effector. I've heard that
some claim that the Octopus' tenticle would make a good hand, but
outside of an aquatic environment, would that still be true?

With some evolution, sure. Why not? The African elephant is very
nimble with its trunk, particularly because this organ, that, only
a few million years ago, used to be an upper lip + nose, managed to
develop two "fingers". The one-"fingered" Indian elephant is less
nimble with its trunk; as I understand it, the African elephant can
pick up a quarter from a smooth surface, and the Indian one can't.

If an upper lip can evolve into something like that, then surely a
tantacle can, given sufficient time and evolutionary pressure.

Personally, I think elephants and squids are very likely candidates
for developing technological intelligence, hadn't we beaten them to
it. But wipe out all vertebrates, add 200 million years, and who
knows what kind of octopoid civilisation might arise here?

For a
traditional hand, you have one thumb and four fingers, for the
minialist hand, you go with three, a thumb and two fingers. I also
recall a robotic hand design that was 'all thumbs' where (any) two of
the thumbs could act as fingers for the other thumb. I think David
Gerrold used that design in one of his Chtorr novels. Its an
interesting design for robotics, but could it be duplicated
organically?

Sure, if there's an advantage. But fingers also have an advantage, and
generally one thumb seems to work fine.

How many arms do you need for an intelligent ET? Some people can get
by with one arm, but they live in a society that was built by two
armed people, could a race of naturally one armed being build a
civilization? Well I guess its possible, but I would imagine it would
require, a lot more team work for simple tasks. Would a third(or
fourth) arm be that useful? I guess it goes back to that an extra
limb requires, extra mass and energy in terms of bone and muscle mass.

Exactly. I don't doubt a single arm (trunk?) or multiple arms (tentacles?)
would work, but it's very possible that two is some sort of optimum.


mcv.
--
Science is not the be-all and end-all of human existence. It's a tool.
A very powerful tool, but not the only tool. And if only that which
could be verified scientifically was considered real, then nearly all
of human experience would be not-real. -- Zachriel
.

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