Theory for Life
Bruce Dunn
Our genetic material is based on a double strand of DNA, with each strand
having the same information in complementary form. DNA damage is repaired by
using the information in the other strand. However, when there is extensive
DNA damage, and the information on both strands at the same spot is destroyed,
an organism has no way of recreating the information.
On planets where life evolves under strong radiation or other DNA damaging
conditions, it is possible that life might evolve with a three-copy genetic
material, in which the information is redundantly stored in three strands (a
sort of triple helix, although the genetic material probably would not resemble
DNA in the least except for the concept that the order of subunits in a linear
polymer encodes the genetic information). Such a genetic material could
withstand destruction of the information in 2 of 3 strands, or resolve
ambiguity in the message by a 2 out of 3 vote. It would thus be much better
suited than a 2 strand system for survival of the genetic message in a hostile
environment.
Higher organisms on earth are usually bilaterally symmetrical. This
probably is a result of the inherent bilateral nature of 1 cell dividing into
two adjacent cells. With triple stranded genetic material, a cell might divide
not into two cells, but into three cells. This would bring up the interesting
idea that extraterrestrial life might be trilaterally symmetrical. The body
form corresponding to our upright posture might then be something like a three
legged creature, with three arms. What then would correspond to the "front"
and "back" of a bilaterally symmetrical creature?
--
Bruce Dunn Vancouver, Canada a7...@mindlink.UUCP
dyu...@cdp.uucp
This is a reply to a posting from Daniel Mocsny on the subject
of THEORIES NEEDED FOR LIFE. I would like to add a couple of
points.
1st: in order to develop technology, the creature must have the
ability to store information external to its brain, or
equivalent, in a nonperishable form. While "pixel-addressable
pigment cells" is a wonderfully creative idea, an alphabet and
printing are more useful.
2nd: the creature must be a predator, otherwise it's species will
spend too much time avoiding being something else's supper. This
will not leave any time for rocketry. It must be at or very near
the top of the trophic web not only for its niche, but also for
the planet. Given the interstellar nature of DNA building
blocks, its meals must be the products of concentrated protien
and other nutrients from intermediate steps in the food chain.
3rd: assuming carbon-based life, sensory organs must be seated as
close as possible to the brain in order to provide the shortest
possible response time between reception of input and reaction to
it. See predator concept above.
4th: having sonar is not inconsistent with predation, and the
creature could 'see' in ultraviolet or infared as well as the
isible light spectrum. If it's body cells concetrated heavy
metals from the environment, there is no reason why it might not
also respond to other wavelengths of the electromagnetic
spectrum. This might result from bioaccumulation of metals
resulting from its predator status.
5th: from what we know of the processing power of our own brains,
there is a trade off of energy expended between physical
coordination or limbs and manipulation of abstract concepts.
This suggests that a creature with four arms or eight elephant
like trunks might spend all its time worrying about where the
parts of its body were and what to do with them, and less time
about its future as a life form or the meaning thereof.
6th: the creature must have the ability to develop abstract
thinking [see #1 above on storage of information] else it will
fail to develop methods for organizing information, and thus fail
to develop technology. This suggests a protective shell of some
kind for the brain or equivalent, else the creature will never
have its mental abilities survive long enough to get the
abstractions built much less communicated. I'm open to
suggestions for candidate materials.
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David Palmer
> Our genetic material is based on a double strand of DNA, with each strand
...
>conditions, it is possible that life might evolve with a three-copy genetic
>material, in which the information is redundantly stored in three strands (a
...
> Higher organisms on earth are usually bilaterally symmetrical. This
>probably is a result of the inherent bilateral nature of 1 cell dividing into
>two adjacent cells. With triple stranded genetic material, a cell might divide
>not into two cells, but into three cells. This would bring up the interesting
>idea that extraterrestrial life might be trilaterally symmetrical. The body
Bilateral symmetry is not the result of cells dividing into pairs.
(IMHO). If that were so, you would expect lower creatures to be
bilaterally symmetric as well, being more raw, crude, and closer to
their original cells (so to speak.) Instead, the more developed an
animal is, the fewer symmetries it has (very roughly).
The lowest animals are roughly spherically symmetric, with symmetry
about any plane passing through their center. Higher animals, such as
sea cucumbers, pine trees (not an animal, strictly speaking, but this
is pop-science, rigor is anathema) sea urchins, worms, etc. are
radially symmetric, symmetric about any plane containing the axis of
the creature. Then we get to the highest levels, including people,
CFAs (cute furry animals), slugs, flatworms, and politicians.
These creatures are symmetric about only a single plane.
Obviously, the next step in evolution is to shed symmetry altogether.
--
David Palmer
pal...@gap.cco.caltech.edu
...rutgers!cit-vax!gap.cco.caltech.edu!palmer
I have the power to cloud men's minds -- or at least my own.
Lucius Chiaraviglio
>This is a reply to a posting from Daniel Mocsny on the subject
>of THEORIES NEEDED FOR LIFE. I would like to add a couple of
>points.
>
>1st: in order to develop technology, the creature must have the
>ability to store information external to its brain, or
>equivalent, in a nonperishable form. While "pixel-addressable
>pigment cells" is a wonderfully creative idea, an alphabet and
>printing are more useful.
Actually, information storage does not absolutely have to be external,
as long as it is sufficiently non-perishable to support the development of a
technological civilization.
>2nd: the creature must be a predator, otherwise it's species will
>spend too much time avoiding being something else's supper. This
>will not leave any time for rocketry.
Does not follow. Perhaps avoiding being someone else's supper might
be a strong selection for intelligence and the development of technology (to
be used against whomever was trying to make supper out of the technological
species). This doesn't seem to have been the primary selective force for the
development of intelligence and technology on Earth, but that doesn't mean it
couldn't be.
> It must be at or very near
>the top of the trophic web not only for its niche, but also for
>the planet.
Why? See above.
> Given the interstellar nature of DNA building
>blocks, its meals must be the products of concentrated protien
>and other nutrients from intermediate steps in the food chain.
Silicate grains seem to be a pretty common interstellar material.
Maybe these are someone's building blocks. Note: I am NOT talking about
using silicon as an analog of carbon. It has been shown that that will not
work. What I am talking about is the use of polysilicates and their
derivatives (silicones, which are very stable, for instance) as a basis for
building blocks. Also, some uses of organic chemistry to form things other
than amino acids and nucleic acids are a possibility.
An aside here: not only do people trying to imagine life on other
worlds have the problem of their imagination tending to be channeled towards
things such as exist on Earth, their imagination tends to be channeled towards
the very small subset of Earth life that they know of. The great majority of
science fiction and serious science (-: well, they try anyway :-) imagination
of life on other worlds imagines things homologous to what most of us see:
plants, animals eating either plant or animal matter, and occasionally fungi.
Mention of microorganisms is generally restricted to diseases, if they are
mentioned at all -- and then often the more serious thought assumes that none
of these would be able to eat anything from Earth, which is likely wrong given
the extraordinary variety of substances that microorganisms can metabolize --
I mean, we really have to do a considerable amount of work to make completely
unmetabolizable organic compounds, and a significant number of inorganic
compounds can serve as food for various organisms. Even among life using only
biochemical pathways found on Earth (almost certainly less diverse than the
biochemical pathways which actually exist on Earth) a staggering variety of
ways to live exists, and an environment different from that which we live in
(but similar to some environments found on Earth) could conceivably select for
a planet-dominating organism very different from us and the organisms we know
with respect to the TYPE of food chain it is in, let alone the position. Such
organisms may have not developed high-order multicellularity and/or
intelligence on Earth simply because their environments are too restricted.
(Actually, one possible such environment we do not know the nature of is the
hydrothermal environment beneath the surface of the mid-ocean ridges, which
take up a substantial fraction of the surface area of our planet -- I forgot
what the number is, but I am pretty sure it is up in the 10% - 20% range.
Maybe a Lovecraftian mass of slime is brooding down there, waiting. . . :-))
>3rd: assuming carbon-based life, sensory organs must be seated as
>close as possible to the brain in order to provide the shortest
>possible response time between reception of input and reaction to
>it. See predator concept above.
For some environments, a factor other than response time might
dominate the placement of sensors relative to the brain. For example, imagine
an organism in a very treacherous and abusive environment. If the organism
could regenerate parts, it could deal with repeated loss of sensors, but even
with regeneration major brain damage would be majorly bad news for retaining
memories needed for civilization. Therefore, it would make sense to either
have the brain as far away as practical (and behind as much shielding as
practical) from all of the common types of abuse, or to have a distributed
redundant form of memory storage so that even a drastically mangled organism
would have a good chance of containing at least one complete copy of its
memories.
>5th: from what we know of the processing power of our own brains,
>there is a trade off of energy expended between physical
>coordination or limbs and manipulation of abstract concepts.
>This suggests that a creature with four arms or eight elephant
>like trunks might spend all its time worrying about where the
>parts of its body were and what to do with them, and less time
>about its future as a life form or the meaning thereof.
Our own brains should not be taken as ultimate examples -- that is, we
should not assume that they represent the full range of what can be done with
a nervous system. To be sure, an organism with more limbs would probably need
a somewhat bigger brain to use them all as well as an organism with fewer
limbs and equal intelligence and equal efficiency of utilization of brain
weight and space, but this does not mean that that is impossible. Also, no
reason exists why a multi-limbed organism could not evolve so as to be able to
choose at will whether to distribute its motor coordination to all limbs or
concentrate most of it on a few so that less brain weight would be required to
control them. As a matter of fact, we can do this to some extent.
>6th: the creature must have the ability to develop abstract
>thinking [see #1 above on storage of information] else it will
>fail to develop methods for organizing information, and thus fail
>to develop technology. This suggests a protective shell of some
>kind for the brain or equivalent, else the creature will never
>have its mental abilities survive long enough to get the
>abstractions built much less communicated. [. . .]
A protective shell would certainly be useful for this, but not the
only means of making memory non-perishable. Having distributed redundant
memory would also work; if suitable high-data-rate communication were a
biological feature of an organism, memory and even thought could be
distributed over multiple physical individuals, so that logical individuals
need not correspond to physical individuals (-: brains like a Sequent :-).
--
| Lucius Chiaraviglio | Internet: ch...@midway.uchicago.edu
kue...@kuhub.cc.ukans.edu
> In article <1050400042@cdp> dyu...@cdp.UUCP writes:
>>This is a reply to a posting from Daniel Mocsny on the subject
>>of THEORIES NEEDED FOR LIFE. I would like to add a couple of
>>points.
>>
As an invertebrate biologist (I specialize in bees), I would also like
to add a couple of points to this discussion - considering the
numerical superiority of invertebrates on our own planet, I tend to
view them as more likely models of lifeforms elsewhere. I have taken
some specific excerpts I'd like to address.
>>2nd: the creature must be a predator, otherwise it's species will
>>spend too much time avoiding being something else's supper. This
>>will not leave any time for rocketry.
>
> Does not follow. Perhaps avoiding being someone else's supper might
> be a strong selection for intelligence and the development of technology (to
> be used against whomever was trying to make supper out of the technological
> species). This doesn't seem to have been the primary selective force for the
> development of intelligence and technology on Earth, but that doesn't mean it
> couldn't be.
>
>> It must be at or very near
>>the top of the trophic web not only for its niche, but also for
>>the planet.
>
> Why? See above.
I concur that this is an unnecessary condition. I think it could be
agreed that among invertebrates, the Cephalopods (octopi, squids, and
their relatives) are probably the "smartest", and yes, they are indeed
predators. BUT: (a) they are also preyed upon by quite a number of
other, less intelligent organisms (b) bees, which would probably come
in second in the intellect ratings, feed on pollen - purely
herbivorous, preyed upon by numerous organisms, and quite bright for
organisms with brains the size of pinheads!(all you Zippy fans...). If
these organisms can get so far without fulfilling the proposed
"requirements", I don't see why they, or organisms like them, could
not, under other conditions, go "all the way" to technology. Can you
consider hive-or-nest-building a primitive technology?
>>3rd: assuming carbon-based life, sensory organs must be seated as
>>close as possible to the brain in order to provide the shortest
>>possible response time between reception of input and reaction to
>>it. See predator concept above.
>
> For some environments, a factor other than response time might
> dominate the placement of sensors relative to the brain. For example, imagine
> an organism in a very treacherous and abusive environment. If the organism
> could regenerate parts, it could deal with repeated loss of sensors, but even
> with regeneration major brain damage would be majorly bad news for retaining
> memories needed for civilization. Therefore, it would make sense to either
> have the brain as far away as practical (and behind as much shielding as
> practical) from all of the common types of abuse, or to have a distributed
> redundant form of memory storage so that even a drastically mangled organism
> would have a good chance of containing at least one complete copy of its
> memories.
>
I might add that proximity is not the only thing that increases the
speed of responses - nerve impulses (in nerves as we know them) travel
at a greater speed in neurons of greater diameter. A great many types
of invertebrates have independently developed "escape neurons" - cells
of great diameter which run directly from a sensory structure to a
motor center. Examples include lobsters, squid, and cockroaches (which
is why they're so tough to step on 8-). In fact (SERIOUS TRIVIA ALERT)
the largest single cell on the Earth is the escape neuron ("giant
axon") of the Giant Squid, _Architeuthis_, which can be around 20 feet
long and an inch in diameter in the larger individuals (presumably to
help them escape from Sperm Whales).
Additionally, the "redundancy" idea expressed above is precisely
the sort of mechanism seen in most Arthropods, in the possession of
segmental ganglia which take care of most motor & reflex responses.
No, not memory storage *per se*, but certain ganglia are capable of
"learning", independently, and so the possibility certainly isn't too
far-fetched. Just watch an insect with its head cut off some time >|-p.
>>5th: from what we know of the processing power of our own brains,
>>there is a trade off of energy expended between physical
>>coordination or limbs and manipulation of abstract concepts.
>>This suggests that a creature with four arms or eight elephant
>>like trunks might spend all its time worrying about where the
>>parts of its body were and what to do with them, and less time
>>about its future as a life form or the meaning thereof.
>
> Our own brains should not be taken as ultimate examples -- that is, we
> should not assume that they represent the full range of what can be done with
> a nervous system. To be sure, an organism with more limbs would probably need
> a somewhat bigger brain to use them all as well as an organism with fewer
> limbs and equal intelligence and equal efficiency of utilization of brain
> weight and space, but this does not mean that that is impossible. Also, no
> reason exists why a multi-limbed organism could not evolve so as to be able to
> choose at will whether to distribute its motor coordination to all limbs or
> concentrate most of it on a few so that less brain weight would be required to
> control them. As a matter of fact, we can do this to some extent.
See my comment on ganglia above, for one, as to relegating motor
activity to peripheral neural structures. Also, squid and octopi seem
to do rather well, for creatures with numerous, extremely dextrous
appendages, don't they?
>>6th: the creature must have the ability to develop abstract
>>thinking [see #1 above on storage of information] else it will
>>fail to develop methods for organizing information, and thus fail
>>to develop technology. This suggests a protective shell of some
>>kind for the brain or equivalent, else the creature will never
>>have its mental abilities survive long enough to get the
>>abstractions built much less communicated. [. . .]
>
> A protective shell would certainly be useful for this, but not the
> only means of making memory non-perishable. Having distributed redundant
> memory would also work; if suitable high-data-rate communication were a
> biological feature of an organism, memory and even thought could be
> distributed over multiple physical individuals, so that logical individuals
> need not correspond to physical individuals (-: brains like a Sequent :-).
>
Again, look at an octopus for a perfect example of an organism with NO
hard covering for its brain, and considerable intellect. I see no
reason they would need to evolve a tougher covering in order to have
greater memory capacity. It does not follow.
> | Lucius Chiaraviglio | Internet: ch...@midway.uchicago.edu
--
----------------------------------------------------------------
Doug Yanega (Snow Museum, Univ. of KS, Lawrence, KS 66045)
My card: 0 The Fool Bitnet: Beeman@ukanvm
"This is my theory, such as it is....which is mine. AAH-HEM!"
Daniel Mocsny
> - considering the
>numerical superiority of invertebrates on our own planet,
...not to mention in my apartment... ;-)
>Can you consider hive-or-nest-building a primitive technology?
A "complex system" consists of a large collection of similar,
relatively simple entities that interact with each other according to
a relatively set of rules/equations. Despite the apparent simplicity
with which we may describe the parts of the system, it may exhibit
arbitrarily complex "emergent" (or "epiphenomenal") behavior.
"Mind" may emerge from the interactions of a large number of relatively
simple neurons. Could it emerge from other complex systems?
Communication appears to be a determining factor in transforming a
collection of parts from a "colony" or "mob" into an "entity" or
"self". I.e., if each component part of the system has an internal
communication bandwidth which greatly exceeds the inter-part bandwidth,
then the capacity for the overall system to act like a unit probably
suffers.
This is intuitively observable in the behavior of human organizations
and communities. People have a hard time holding social structures
together---nations and businesses collapse, are overthrown, ethnic
groups balkanize, etc. This is easy to predict from the simple fact
that every particular individual enjoys a much richer communication
between parts of his own brain than with other brains. The result is
endless misunderstanding and conflict between humans. Conversely, the
more people "talk" to each other, USENET notwithstanding ;-), the more
likely they are to identify with a group than with themselves as
individuals. (More than just "talk" is involved, of course, since human
brains obtain information from the environment in several ways.)
In practical terms, the most essential component of all successful
social organizations is how well they manage information. In light of
modern organizational failures, one wonders how the great empires of
ancient times managed to "exist", or what this "existence" really
meant in the day-to-day affairs of people living in them.
Getting back to the hive-mind possibility:
I suspect that any "Mind" emerging from a community of bees might not
develop much of an IQ. The problems:
1. The maximum practical size of a hive is limited. The human brain
has about 1e+11 components. A single bee is more complex than a single
neuron, of course. However, in terms of its interaction with the hive,
it is probably not vastly more complex. For the small system of
a few thousands of bees to become "Mind", each bee would have to
embed a comsiderable degree of intelligence. This brings us to the
next problem.
2. Intra-bee communication is by neural pathways. This is several
orders of magnitude faster than inter-bee communication, which is
by tactile, visual, and chemical pathways. Unless bees can come up
with a way to "talk" faster, the overall performance of the hive-mind
will be very slow. If it is too slow, it will only be able to respond
to environmental phenomena that operate with slow characteristic times.
For example, the hive-mind can track changes in the location of the
best pollen fields.
The slow inter-bee communication also probably limits the extent to
which the hive subsumes each individual bee. For example, each bee
is capable of existing in the real world (to some extent) independently
from the hive. This is not possible at all for a neuron in the brain.
The hive-mind simply isn't fast and powerful enough to safeguard the
momentary existence of each bee. Thus each bee must be a self-contained
survival machine. This gives each bee a self-interest and identity
apart from the hive. To the extent that each bee can stand on its
own six feet, the hive-mind must be limited.
--
Dan Mocsny Snail:
Internet: dmo...@minerva.che.uc.edu Dept. of Chemical Engng. M.L. 171
dmo...@uceng.uc.edu University of Cincinnati
513/751-6824 (home) 513/556-2007 (lab) Cincinnati, Ohio 45221-0171
Brian or James
[material deleted]
>Obviously, the next step in evolution is to shed symmetry altogether.
*What* 'next step'? The history of evolution on Earth is not
a record of lower organisms endlessly striving to achieve 'higher rungs
on the ladder of life [Upper rung usually defined as 'Most like the
writer of the essay in question']. The phrase 'next step' suggests to me
a predesign or goal that life strive to attain, and I don't think the evidence
supports this view of evolution.
James Nicoll
Larry Wall
I'd give my right arm for that.
kue...@kuhub.cc.ukans.edu
Um, you can save the arm - sponges (as in "the group of animals that
is so primitive that many authorities put them in their own little
subkingdom") have had no symmetry for millions of years now. I guess
"couch potato" and sponge aren't so far removed, though - gee, we've
almost come full circle! ;-)