I've been listening to SETI's radio show 'Are We Alone' and once in
awhile when the subject of what would Inteligent ET look like, they
always dismiss that 'they' would not look anything like us. 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! Well, I wouldn't
expect them to look exactly like us. But what is so wrong with our
bipedal, bilaterally symetric body plan?
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. 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?

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?
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. 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. 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)?

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? 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?
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.

Here is a design,(maybe a bit on the absurd side) of a minimalist
alien body plan.
A cycloptic monoped. It has one eye mounted on arm stalk, like a
Pierson's Puppeteer, with the same mouth/hand functionallity. It has
one leg that it hops around on for locomotion, the brain & other vital
organs are stored in the center in a large boney hump. Sort of a
mutant or crippled Pierson's Puppeteer.

Just my $0.02

Space Cadet

derwetzelsDASHspacecadetATyahooDOTcom


Moon Society - St. Louis Chapter

http://www.moonsociety.org/chapters/stlouis/

The Moon Society is a non-profit educational and
scientific foundation formed to further scientific
study and development of the moon.

Space Cadet <kaw211@gmail.com> 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

> > 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?

Bigger question about puppeteer bodyplan is not how it came to have
three legs, but how it came to have two throats. All Earth vertebrates
developed from a lancet-like ancestor with tube-shape bodyplan --
topologically, they all are toruses (tori?). Flatworms, cnidarians,
and other animals without complete digestive tract are, topologically,
spheres. The ancestor of puppeteers' phylum must have had Y-shaped
bodyplan, which is a topological shape that does not occur in Earth
bodyplans.

ilya2@rcn.com schrieb:
>>> 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?
>
> Bigger question about puppeteer bodyplan is not how it came to have
> three legs, but how it came to have two throats. All Earth vertebrates
> developed from a lancet-like ancestor with tube-shape bodyplan --
> topologically, they all are toruses (tori?). Flatworms, cnidarians,
> and other animals without complete digestive tract are, topologically,
> spheres. The ancestor of puppeteers' phylum must have had Y-shaped
> bodyplan, which is a topological shape that does not occur in Earth
> bodyplans.

A starfish whose prongs develop secondary respiratory systems (possible
from the water vessels) should get you multiple throats just fine.

mawa

On Jan 2, 11:50 am, il...@rcn.com wrote:
> > > 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?
>
> Bigger question about puppeteer bodyplan is not how it came to have
> three legs, but how it came to have two throats. All Earth vertebrates
> developed from a lancet-like ancestor with tube-shape bodyplan --
> topologically, they all are toruses (tori?). Flatworms, cnidarians,
> and other animals without complete digestive tract are, topologically,
> spheres. The ancestor of puppeteers' phylum must have had Y-shaped
> bodyplan, which is a topological shape that does not occur in Earth
> bodyplans.

Has Niven been clear that the throats connect to an orifice at the
other end? If one or both throats aren't complete, or each one leads
to a different, parallel, digestive system, all sorts of possibilities
open up.

For the third leg, I recall speculation that the rear leg formed from
two fused hind legs -- at some point the turn-and-kick technique must
have become more advantageous than quadrupedal locomotion. IIRC,
drawings of the Puppeteers in Barlowe's book suggest two legs fused at
the knee.

--
DJensen

On Dec 30 2007, 10:16 pm, Space Cadet <kaw...@gmail.com> wrote:
> I've been listening to SETI's radio show 'Are We Alone' and once in
> awhile when the subject of what would Inteligent ET look like, they
> always dismiss that 'they' would not look anything like us. 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! Well, I wouldn't
> expect them to look exactly like us. But what is so wrong with our
> bipedal, bilaterally symetric body plan?

There's nothing wrong with bilateral symmetry, but it's not the only
kind that has arisen on Earth either. (Is there a term for the broken
bilateral symmetry of fiddler crabs and such?)

> 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.

'Need' is rather tricky. There are plenty of examples of life on Earth
that 'need' 6 or more legs, plenty that have no legs at all, lots that
have 8 or 10, and some that only have two and a tail -- and we
consider some members of the latter two sets to be quite intelligent.

> 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.

In terms of 'efficiency' and stability, knuckle-walking quadrupeds
might be the next best thing: four 'legs', but two of them sport
hands. A centauroid plan, with four legs and two arms (or two true
legs, two true arms, and two that can switch roles, like the knuckle-
walkers) seems like a stable and the next most minimal arrangement.

> 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?

Something like the cuttlefish eye, I imagine, should be able to
achieve binocular vision; cuttlefish have fovea arranged to see
forward and backward simultaneously.

> 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? 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

I wonder if two thumbs (one on either side) and a finger would be
effective.

> 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.

Anything less than two true hands and I think it's unlikely to catch
on. Normally I don't go for the "if you lose one" arguments in
hypothetical alien evolution, but if you only have one hand and you
lose it in a world full of predators, your nascent intelligence won't
get you very far.

--
DJensen

On Jan 2, 4:12 pm, DJensen <i_m...@yahoo.ca> wrote:
> On Dec 30 2007, 10:16 pm, Space Cadet <kaw...@gmail.com> wrote:
>
>
>
> There's nothing wrong with bilateral symmetry, but it's not the only
> kind that has arisen on Earth either. (Is there a term for the broken
> bilateral symmetry of fiddler crabs and such?)

>
> --
> DJensen

First, I would like to chime in and say that the only other symmetry I
know of is radial symmetry, like a starfish. Secondly, while humans
are certainly not the strongest or fastest species on the planet, we
don't need to be- we're powerful enough to reshape the planet as we
see fit. And considering how evolution doesn't just add new traits,
but strip away useless ones, a sentient alien species would probably
be like us- while its physical shape probably isn't top model on their
planet, they're smart enough to compensate for it, and their bodies
will be efficient enough to get around.

John schrieb:
> On Jan 2, 4:12 pm, DJensen <i_m...@yahoo.ca> wrote:
>> On Dec 30 2007, 10:16 pm, Space Cadet <kaw...@gmail.com> wrote:
>>
>>
>>
>> There's nothing wrong with bilateral symmetry, but it's not the only
>> kind that has arisen on Earth either. (Is there a term for the broken
>> bilateral symmetry of fiddler crabs and such?)
>
>> --
>> DJensen
>
> First, I would like to chime in and say that the only other symmetry I
> know of is radial symmetry, like a starfish.

ISTR that even in starfish, radial symmetry is a secondary development
overlaying a plan that is fundamentally bilaterally symmetric.

mawa

On Jan 7, 12:36 am, John <themast...@gmail.com> wrote:

> considering how evolution doesn't just add new traits,
> but strip away useless ones, a sentient alien species
> would probably be like us...

There are a number of assumptions there. First, that "evolution"
strips away useless ones, *and which adaptations are useless*. For
instance, immunity to sickle cell would seem something good... and
residual body hair and having your retina build backwards could be
construed as useless (or even a liability), and yet are still around.

Personally I don't see anything all that advantageous about our
current upright, bilateral, rather cobbled together body plan... but
that's very much the way evolution works. And about the only thing
that's certain is that there's no reason to think the same result
would come up the second time around.

--
Brian Davis

John <themasterJ@gmail.com> wrote:
> First, I would like to chime in and say that the only other symmetry I
> know of is radial symmetry, like a starfish. Secondly, while humans
> are certainly not the strongest or fastest species on the planet, we
> don't need to be- we're powerful enough to reshape the planet as we
> see fit. And considering how evolution doesn't just add new traits,
> but strip away useless ones, a sentient alien species would probably
> be like us- while its physical shape probably isn't top model on their
> planet, they're smart enough to compensate for it, and their bodies
> will be efficient enough to get around.

We may not be the strongest or the fastest but that doesn't mean we're the
best at nothing. It's a popular meme that humans are jacks of all trades,
masters of none, but it's not true. Aside from the obvious advantage in
intelligence, and related stuff like manual dexterity, we're also the
planet's supreme endurance runners. Other animals may be faster but none
can keep it up like we can. Indeed an ancient hunting technique is simply
to find an animal and then chase it until it collapses from exhaustion,
and then kill it.

Obviously our intelligence is a huge advantage and a qualitative
difference from all the other animals, but it doesn't help make up for
physical inferiority, but rather enhances our ability to use our physical
superiority.

--
Michael Ash
Rogue Amoeba Software

On Dec 30 2007, 9:16 pm, Space Cadet <kaw...@gmail.com> wrote:

> 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.

On Earth, most life doesn't really have limbs, and higher order
vertibrate life usually has six limbs (four legs, a flexible neck,
and a flexible tail).

> 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.  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?

Two forelegs with a single rear leg? That much is plausible,
since we see a similar configuration in kangaroos and some birds.

> 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?

Yes, especially if it's a sort of compound eye or lobster eye with
a wide field of view. Note that some insects, like dragonflies, have
eyes which are practically a single continuous eye with two lobes.

> 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.

None of that is necessary for depth perception. You need only
cover one of your eyes to see that. Still, two eyes help provide
more accurate depth perception.

One exotic possibility would be vertically spaced eyes rather
than horizontal. Maybe one central compound eye splits into
an upper half optimized for seeing above water, and a lower
half optimized for seeing below water. Then they split apart.

> 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.  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 seems that two eyes are sufficient for nearly all-around vision,
if the eyes are rotateable by the ball-and-socket method.
However, spider eyes have fixed lenses and they rotate their
field of view by shifting the retina around. This severely limits
the degree to which they can swivel the field of view. Spiders
have multiple eyes to see all around.

> 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?  For a
> traditional hand, you have one thumb and four fingers, for the
> minialist hand, you go with three, a thumb and two fingers.

Or a tongue and two halves of a beak. Birds are capable of
impressive feats of construction.

> 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.

A requirement for more teamwork could be an evolutionary
boost, giving greater advantage to those with greater intelligence
and sophisticated communications capability.

>  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.

We gave up our tails, but it's entirely plausible that the awkward
position of the tail made it less useful.

> Here is a design,(maybe a bit on the absurd side) of a minimalist
> alien body plan.
> A cycloptic monoped.  It has one eye mounted on arm stalk, like a
> Pierson's Puppeteer, with the same mouth/hand functionallity. It has
> one leg that it hops around on for locomotion, the brain & other vital
> organs are stored in the center in a large boney hump.  Sort of a
> mutant or crippled Pierson's Puppeteer.

Something vaguely bird-like could evolve into this. First, let's
note that many small birds hop rather than walk. If their neural
systems get hardwared into this sort of motion, ala kangaroos,
then the two legs could get merged into one leg. We can assume
the wings get lost ala flightless kiwi birds. That leaves just one
hopping leg.

Somewhere early in the fish-like evolutionary stage could be
when the single eye structure evolved. It could have started
with compound eyes like a dragonfly--a single large sphere
centered around a small central brain. This configuration
provides the absolute minimum optic nerve lengths and thus
the fastest possible reaction times. A more predatory
lifestyle could lead to the elements concentrating forward
and at some point it mutates into a single lens eye. This
is a mutation involving a lack of pigmentation in the walls
between the compount eye elements. If the curvature of
the outer eye and the distance to the photosensors is
just right, this mutation will provide a much brighter image,
albeit upside-down.

After the eye evolves into a lensed configuration, it's
permanently set as one eye and can't easily split up into
two eyes again (as would be possible with compound
eyes). So these fish-like animals have a single central eye.
Ideal? No. But they have no choice but to deal with it.

Isaac Kuo

On Jan 7, 12:48 pm, IsaacKuo <mech...@yahoo.com> wrote:
> On Dec 30 2007, 9:16 pm, Space Cadet <kaw...@gmail.com> wrote:
>
> > 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.
>
> On Earth, most life doesn't really have limbs, and higher order
> vertibrate life usually has six limbs (four legs, a flexible neck,
> and a flexible tail).

You're confusing limb with appendage. A limb is by definition not part
of the head/trunk structure and is prehensile.

> > 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?
>
> Two forelegs with a single rear leg? That much is plausible,
> since we see a similar configuration in kangaroos and some birds.

Isn't that like saying snakes have one leg and crocodiles have 5?
Using it as a resting surface shouldn't get it to count as a leg.

> > 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.
>
> We gave up our tails, but it's entirely plausible that the awkward
> position of the tail made it less useful.

If our ancestor's pelvic bones were a bit different the tail might
have helped them balance, and we'd look more like hunchbacked
therapods than stretched out chimps. I think it's more likely we lost
our tails because we weren't climbing in the trees anymore.

> > Here is a design,(maybe a bit on the absurd side) of a minimalist
> > alien body plan.
> > A cycloptic monoped. It has one eye mounted on arm stalk, like a
> > Pierson's Puppeteer, with the same mouth/hand functionallity. It has
> > one leg that it hops around on for locomotion, the brain & other vital
> > organs are stored in the center in a large boney hump. Sort of a
> > mutant or crippled Pierson's Puppeteer.
>
> Something vaguely bird-like could evolve into this. First, let's
> note that many small birds hop rather than walk. If their neural
> systems get hardwared into this sort of motion, ala kangaroos,
> then the two legs could get merged into one leg. We can assume
> the wings get lost ala flightless kiwi birds. That leaves just one
> hopping leg.

Some birds may hop instead of walk, but they also stand still and
climb. One leg would make that quite difficult (particularly the
latter), so I don't think that's likely. It's plausible they'd both
become vestigial, as with pinnipeds. Snakes with beaks and feathers,
hmmm.

--
DJensen

On Jan 7, 12:36 am, John <themast...@gmail.com> wrote:
> On Jan 2, 4:12 pm, DJensen <i_m...@yahoo.ca> wrote:
> > There's nothing wrong with bilateral symmetry, but it's not the only
> > kind that has arisen on Earth either. (Is there a term for the broken
> > bilateral symmetry of fiddler crabs and such?)
>
> First, I would like to chime in and say that the only other symmetry I
> know of is radial symmetry, like a starfish. Secondly, while humans
> are certainly not the strongest or fastest species on the planet, we
> don't need to be- we're powerful enough to reshape the planet as we
> see fit. And considering how evolution doesn't just add new traits,
> but strip away useless ones, a sentient alien species would probably
> be like us- while its physical shape probably isn't top model on their
> planet, they're smart enough to compensate for it, and their bodies
> will be efficient enough to get around.

Sample of one. What if intelligence becomes an advantage only after
the species has become the size of blue whales?

--
DJensen

On Jan 7, 2:11 pm, DJensen <i_m...@yahoo.ca> wrote:
> On Jan 7, 12:48 pm, IsaacKuo <mech...@yahoo.com> wrote:

> > On Dec 30 2007, 9:16 pm, Space Cadet <kaw...@gmail.com> wrote:

> > > 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.

> > On Earth, most life doesn't really have limbs, and higher order
> > vertibrate life usually has six limbs (four legs, a flexible neck,
> > and a flexible tail).

> You're confusing limb with appendage. A limb is by definition not part
> of the head/trunk structure and is prehensile.

An arbitrary and artificial distinction. What really matters is
what the thing does. If a bird's beak can be used to weave
nests as skillfully as any mammal hand, then mother nature
doesn't sweat the difference. If a kangaroo tail can be used
just like a third leg, then mother nature doesn't sweat the
difference.

> > > 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?

> > Two forelegs with a single rear leg?  That much is plausible,
> > since we see a similar configuration in kangaroos and some birds.

> Isn't that like saying snakes have one leg and crocodiles have 5?
> Using it as a resting surface shouldn't get it to count as a leg.

Kangaroos don't just use their rear tails as a resting surface.
When walking, they use it like a third leg--actually, they use
it like a second leg since the first two legs neurologically
act in unison.

Neither snakes nor crocodiles use their tails in a leg-like
manner.

> > >  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.

> > We gave up our tails, but it's entirely plausible that the awkward
> > position of the tail made it less useful.

> If our ancestor's pelvic bones were a bit different the tail might
> have helped them balance, and we'd look more like hunchbacked
> therapods than stretched out chimps. I think it's more likely we lost
> our tails because we weren't climbing in the trees anymore.

If our tails were in a more convenient location to cooperate with
our hands, we would have kept them anyway. We kept our
hands even though we weren't climbing in the trees anymore.

For example, suppose our ancestors used an elephant-like
nose to help tree-climbing rather than a prehensile tail. We
would have kept it because it would still be in a useful
position.

> > > Here is a design,(maybe a bit on the absurd side) of a minimalist
> > > alien body plan.
> > > A cycloptic monoped.  It has one eye mounted on arm stalk, like a
> > > Pierson's Puppeteer, with the same mouth/hand functionallity. It has
> > > one leg that it hops around on for locomotion, the brain & other vital
> > > organs are stored in the center in a large boney hump.  Sort of a
> > > mutant or crippled Pierson's Puppeteer.

> > Something vaguely bird-like could evolve into this.  First, let's
> > note that many small birds hop rather than walk.  If their neural
> > systems get hardwared into this sort of motion, ala kangaroos,
> > then the two legs could get merged into one leg.  We can assume
> > the wings get lost ala flightless kiwi birds.  That leaves just one
> > hopping leg.

> Some birds may hop instead of walk, but they also stand still and
> climb. One leg would make that quite difficult (particularly the
> latter), so I don't think that's likely.

It's not at all hard to stand on one leg. Flamingos do it for hours
at a time, and they even have to go through the extra effort of
holding the other leg up. It's simply a matter of having long toes
spread out over a wide angle (very common among birds).

As for climbing--not all birds climb. Obviously, most birds can
fly so they don't really need to climb. But none of the flightless
birds climb either.

> It's plausible they'd both
> become vestigial, as with pinnipeds. Snakes with beaks and feathers,
> hmmm.

Sure, that's also a possibility. It just isn't a possibility that
leads
in the direction of that cycloptic monoped idea.

Isaac Kuo

On Mon, 07 Jan 2008 11:53:43 +0100, Matthias Warkus
<Warkus@students.uni-marburg.de> wrote:

>John schrieb:
>> On Jan 2, 4:12 pm, DJensen <i_m...@yahoo.ca> wrote:
>>> On Dec 30 2007, 10:16 pm, Space Cadet <kaw...@gmail.com> wrote:

>>> There's nothing wrong with bilateral symmetry, but it's not the only
>>> kind that has arisen on Earth either. (Is there a term for the broken
>>> bilateral symmetry of fiddler crabs and such?)

>> First, I would like to chime in and say that the only other symmetry I
>> know of is radial symmetry, like a starfish.

>ISTR that even in starfish, radial symmetry is a secondary development
>overlaying a plan that is fundamentally bilaterally symmetric.

Starfish, yes. But there are other critters, e.g. jellyfish, which are
truly radially symmetrical. Not sure if there's anything with true
fivefold radial symmetry, though.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
*John.Schilling@alumni.usc.edu * for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

On Jan 7, 4:29 pm, IsaacKuo <mech...@yahoo.com> wrote:
> On Jan 7, 2:11 pm, DJensen <i_m...@yahoo.ca> wrote:
> > On Jan 7, 12:48 pm, IsaacKuo <mech...@yahoo.com> wrote:
> > > On Earth, most life doesn't really have limbs, and higher order
> > > vertibrate life usually has six limbs (four legs, a flexible neck,
> > > and a flexible tail).
> > You're confusing limb with appendage. A limb is by definition not part
> > of the head/trunk structure and is prehensile.
>
> An arbitrary and artificial distinction. What really matters is
> what the thing does. If a bird's beak can be used to weave
> nests as skillfully as any mammal hand, then mother nature
> doesn't sweat the difference. If a kangaroo tail can be used
> just like a third leg, then mother nature doesn't sweat the
> difference.

All the same, we make a distinction between limbs and appendages. An
appendage can be *used* to manipulate things, whether it's weaving a
nest with a beak, tying a cherry stem in a knot with your tongue, or
using your butt cheek to push the fridge door closed, but calling a
tail a leg doesn't make it one.

> > > Two forelegs with a single rear leg? That much is plausible,
> > > since we see a similar configuration in kangaroos and some birds.
> > Isn't that like saying snakes have one leg and crocodiles have 5?
> > Using it as a resting surface shouldn't get it to count as a leg.
>
> Kangaroos don't just use their rear tails as a resting surface.
> When walking, they use it like a third leg--actually, they use
> it like a second leg since the first two legs neurologically
> act in unison.

I've only seen it used as a prop when they lean back or straighten up
to 'box'. In fact when walking they use their forelimbs, not their
tails.

> Neither snakes nor crocodiles use their tails in a leg-like
> manner.

That was my point. Neither do kangaroos.

> > > We gave up our tails, but it's entirely plausible that the awkward
> > > position of the tail made it less useful.
> > If our ancestor's pelvic bones were a bit different the tail might
> > have helped them balance, and we'd look more like hunchbacked
> > therapods than stretched out chimps. I think it's more likely we lost
> > our tails because we weren't climbing in the trees anymore.
>
> If our tails were in a more convenient location to cooperate with
> our hands, we would have kept them anyway. We kept our
> hands even though we weren't climbing in the trees anymore.

They didn't feed themselves with their feet and tails. They kept their
hands because they were still using them for pretty much the same
thing as in the trees.

> > Some birds may hop instead of walk, but they also stand still and
> > climb. One leg would make that quite difficult (particularly the
> > latter), so I don't think that's likely.
>
> It's not at all hard to stand on one leg. Flamingos do it for hours
> at a time, and they even have to go through the extra effort of
> holding the other leg up. It's simply a matter of having long toes
> spread out over a wide angle (very common among birds).
>
> As for climbing--not all birds climb. Obviously, most birds can
> fly so they don't really need to climb. But none of the flightless
> birds climb either.

All flying birds that nest anywhere but on the ground in the open,
climb. If they couldn't they couldn't built or access their nests.
Climbing is useful for other things too -- like mating.

--
DJensen

In article
<d7465266-d9e0-40e8-9dc0-d0f1ace936d7@i29g2000prf.googlegroups.com>,
DJensen <i_m0nk@yahoo.ca> wrote:

> On Jan 7, 4:29 pm, IsaacKuo <mech...@yahoo.com> wrote:
> > On Jan 7, 2:11 pm, DJensen <i_m...@yahoo.ca> wrote:
> > > On Jan 7, 12:48 pm, IsaacKuo <mech...@yahoo.com> wrote:
>
> > > > Two forelegs with a single rear leg? That much is plausible,
> > > > since we see a similar configuration in kangaroos and some birds.
> > > Isn't that like saying snakes have one leg and crocodiles have 5?
> > > Using it as a resting surface shouldn't get it to count as a leg.
> >
> > Kangaroos don't just use their rear tails as a resting surface.
> > When walking, they use it like a third leg--actually, they use
> > it like a second leg since the first two legs neurologically
> > act in unison.
>
> I've only seen it used as a prop when they lean back or straighten up
> to 'box'. In fact when walking they use their forelimbs, not their
> tails.


Here's some Youtube of kangaroos walking in pentapedal mode, with their
forelimbs and with their tail as leg 5. I have also seen tripedal
walking, but I can't find a video of it on a brief search.
http://www.youtube.com/watch?v=ZZx9AQ1QGtA

--
David M. Palmer dmpalmer@email.com (formerly @clark.net, @ematic.com)

On Jan 7, 10:06 pm, DJensen <i_m...@yahoo.ca> wrote:
> On Jan 7, 4:29 pm, IsaacKuo <mech...@yahoo.com> wrote:

> > > > We gave up our tails, but it's entirely plausible that the awkward
> > > > position of the tail made it less useful.
> > > If our ancestor's pelvic bones were a bit different the tail might
> > > have helped them balance, and we'd look more like hunchbacked
> > > therapods than stretched out chimps. I think it's more likely we lost
> > > our tails because we weren't climbing in the trees anymore.

> > If our tails were in a more convenient location to cooperate with
> > our hands, we would have kept them anyway. We kept our
> > hands even though we weren't climbing in the trees anymore.

> They didn't feed themselves with their feet and tails. They kept their
> hands because they were still using them for pretty much the same
> thing as in the trees.

If the "tail" were in a different position convenient for feeding
themselves with, then it would have been used for that also.

> > > Some birds may hop instead of walk, but they also stand still and
> > > climb. One leg would make that quite difficult (particularly the
> > > latter), so I don't think that's likely.

> > It's not at all hard to stand on one leg. Flamingos do it for hours
> > at a time, and they even have to go through the extra effort of
> > holding the other leg up. It's simply a matter of having long toes
> > spread out over a wide angle (very common among birds).

> > As for climbing--not all birds climb. Obviously, most birds can
> > fly so they don't really need to climb. But none of the flightless
> > birds climb either.

> All flying birds that nest anywhere but on the ground in the open,
> climb. If they couldn't they couldn't built or access their nests.

Doesn't affect my assertion that not ALL birds climb, particularly
flightless birds.

> Climbing is useful for other things too -- like mating.

Animals with extremely short legs or legs lost due to injury
manage to mate anyway. Here in Louisiana, a mutation led
to short-legged housecats. Their legs are simply too short
to easily mate the normal way, so they mate belly-to-belly.

Isaac Kuo

On Jan 7, 8:06 pm, DJensen <i_m...@yahoo.ca> wrote:

> All flying birds that nest anywhere but on the ground in the open,
> climb. If they couldn't they couldn't built or access their nests.
> Climbing is useful for other things too -- like mating.

A counter-example is hummingbirds. These fly, they nest in bushes and
trees, and their legs cannot be used for anything except perching.
They cannot even walk or hop, let alone climb. Hummers fly wherever
they need to go.

Luke

On Jan 8, 6:52 am, IsaacKuo <mech...@yahoo.com> wrote:
> On Jan 7, 10:06 pm, DJensen <i_m...@yahoo.ca> wrote:
> > On Jan 7, 4:29 pm, IsaacKuo <mech...@yahoo.com> wrote:
> > > If our tails were in a more convenient location to cooperate with
> > > our hands, we would have kept them anyway. We kept our
> > > hands even though we weren't climbing in the trees anymore.
> > They didn't feed themselves with their feet and tails. They kept their
> > hands because they were still using them for pretty much the same
> > thing as in the trees.
>
> If the "tail" were in a different position convenient for feeding
> themselves with, then it would have been used for that also.

I wasn't saying anything about other tail positions. You implied that
our ancestors only used their hands in tree climbing, and it was some
sort of oddity that we still have them now. If our ancestors were
anything ape-like at all, they used their hands for collecting food
and eating, grooming, and any number of other things before they came
down from the branches.

> > > As for climbing--not all birds climb. Obviously, most birds can
> > > fly so they don't really need to climb. But none of the flightless
> > > birds climb either.
> > All flying birds that nest anywhere but on the ground in the open,
> > climb. If they couldn't they couldn't built or access their nests.
>
> Doesn't affect my assertion that not ALL birds climb, particularly
> flightless birds.

"Most birds can fly so they don't really need to climb" was your
claim. That's what I addressed.

--
DJensen

On Jan 8, 12:40 am, "David M. Palmer" <dmpal...@email.com> wrote:
> DJensen <i_m...@yahoo.ca> wrote:
> > On Jan 7, 4:29 pm, IsaacKuo <mech...@yahoo.com> wrote:
> > > Kangaroos don't just use their rear tails as a resting surface.
> > > When walking, they use it like a third leg--actually, they use
> > > it like a second leg since the first two legs neurologically
> > > act in unison.
>
> > I've only seen it used as a prop when they lean back or straighten up
> > to 'box'. In fact when walking they use their forelimbs, not their
> > tails.
>
> Here's some Youtube of kangaroos walking in pentapedal mode, with their
> forelimbs and with their tail as leg 5. I have also seen tripedal
> walking, but I can't find a video of it on a brief search.http://www.youtube.com/watch?v=ZZx9AQ1QGtA

It's not clear to me that they're using their tail like a leg at all.
A prop perhaps, but it's not clear where they're putting their weight
or if the tail is pushing forward.

--
DJensen

On Jan 8, 11:35 am, DJensen <i_m...@yahoo.ca> wrote:
> On Jan 8, 6:52 am, IsaacKuo <mech...@yahoo.com> wrote:

> > On Jan 7, 10:06 pm, DJensen <i_m...@yahoo.ca> wrote:
> > > On Jan 7, 4:29 pm, IsaacKuo <mech...@yahoo.com> wrote:
> > > > If our tails were in a more convenient location to cooperate with
> > > > our hands, we would have kept them anyway. We kept our
> > > > hands even though we weren't climbing in the trees anymore.
> > > They didn't feed themselves with their feet and tails. They kept their
> > > hands because they were still using them for pretty much the same
> > > thing as in the trees.

> > If the "tail" were in a different position convenient for feeding
> > themselves with, then it would have been used for that also.

> I wasn't saying anything about other tail positions. You implied that
> our ancestors only used their hands in tree climbing, and it was some
> sort of oddity that we still have them now.

I'm sorry you misinterpreted my words.

What I meant to imply was that we kept our hands because
they were used for things other than just climbing trees.
Therefore, if our "tails" were in a different position where
they were useful for things other than just climbing trees,
they'd be kept also.

It's the same point I've been repeating several times, now.

Getting back to the original context, all I said was that we
may have lost our tails simply because they were in a
less useful position. Had our "tails" been in a more
useful position capable of working with our hands, then
we may not have lost them.

> > > > As for climbing--not all birds climb. Obviously, most birds can
> > > > fly so they don't really need to climb. But none of the flightless
> > > > birds climb either.
> > > All flying birds that nest anywhere but on the ground in the open,
> > > climb. If they couldn't they couldn't built or access their nests.

> > Doesn't affect my assertion that not ALL birds climb, particularly
> > flightless birds.

> "Most birds can fly so they don't really need to climb" was your
> claim. That's what I addressed.

And so what? Even if what you said were true, it doesn't affect my
point. What's your point?

It's not actually necessary to build nests anywhere but on the
ground, and it's not necessary to climb in order to build nests in
trees or on cliffs, and it's certainly possible to pick apart your
assertion in detail, but...who cares?

None of it has any relevance to the main point, which is that
many birds, including flightless birds, do just fine without climbing.
It's not necessary to climb, so climbing isn't a requirement which
will necessarily prevent bird-like aliens from evolving into
one-legged beings.

Isaac Kuo

On Jan 7, 10:01 am, Michael Ash <m...@mikeash.com> wrote:

> we're also the planet's supreme endurance runners.

No, we're not.

Oh, we're damn good, but there are a few critters that can still beat
us in the long haul. The pronghorn antelope is both a speed and
endurance champion, IIRC, the mongolian wild *** is also a long-haul
specialist, and although I don't know of any specific studies, given
that they've been selectively bred for endurance for many, many
generations, I'd bet on a good sled dog over any given human in a
cross-country marathon.

Knobby <knobbynobbs@hotmail.com> wrote:
> On Jan 7, 10:01 am, Michael Ash <m...@mikeash.com> wrote:
>
>> we're also the planet's supreme endurance runners.
>
> No, we're not.
>
> Oh, we're damn good, but there are a few critters that can still beat
> us in the long haul. The pronghorn antelope is both a speed and
> endurance champion, IIRC, the mongolian wild *** is also a long-haul
> specialist, and although I don't know of any specific studies, given
> that they've been selectively bred for endurance for many, many
> generations, I'd bet on a good sled dog over any given human in a
> cross-country marathon.

Interesting. Are these animals really capable of running dozens or
hundreds of miles without stopping? I guess you can't be the absolute
best. Thanks for the info.

--
Michael Ash
Rogue Amoeba Software

Wasn't it Michael Ash who wrote:
>Knobby <knobbynobbs@hotmail.com> wrote:
>> On Jan 7, 10:01 am, Michael Ash <m...@mikeash.com> wrote:
>>
>>> we're also the planet's supreme endurance runners.
>>
>> No, we're not.
>>
>> Oh, we're damn good, but there are a few critters that can still beat
>> us in the long haul. The pronghorn antelope is both a speed and
>> endurance champion, IIRC, the mongolian wild *** is also a long-haul
>> specialist, and although I don't know of any specific studies, given
>> that they've been selectively bred for endurance for many, many
>> generations, I'd bet on a good sled dog over any given human in a
>> cross-country marathon.
>
>Interesting. Are these animals really capable of running dozens or
>hundreds of miles without stopping? I guess you can't be the absolute
>best. Thanks for the info.
>
Human endurance hunters use the trick of carrying a little food and
water with them. The animals that they're tracking can't do that. In
places where water is scarce the hunters can steer the prey away from
known water sources and easy grazing.

--
Mike Williams
Gentleman of Leisure