I don't recall if the last time I argued this was just on >H or here, so
I'll recap:
While some people have postulated the possiblity of life based on
silicon, it simply does not have the same number of possible valence
combinations as carbon does. While silicon life may form in some carbon
poor regions of the universe (unlikely that such a state could exist,
but not impossible), anywhere where carbon is in its normal abundance,
and temperatures exist between -20 C up to 150 C, and there is water,
life will form around carbon. Any silicon based primitive life forms
will quickly be pushed out of the competition for resources with its
carbon cousins because of carbon's greater ability to form complex
molecules.
So we know that carbon life will dominate, at least on Earthlike worlds.
Furthermore, any possible life forms developing on planets vastly
dissimilar to our own would of neccessity have vastly different goals,
resource needs, and would not compete with us for planets, as what we
would find optimum would not neccessarily be optimum for such vastly
different life forms, so we would probably have little interaction
outside of information trade, assuming that we could even communicate.
So, given this, our greatest probable interactions with alien life forms
will be on earthlike worlds, or near earthlike worlds (as such will be
our main objects of attention for colonization), enough that they will
be carbon based life forms that we will deal with.
Now given this, we can look at the various life forms developed on our
own planet (while this may seem limiting, it is the only dataset we can
go on at the moment). I beleive that given the separation of continents
for millions of years is sufficient to derive a decent idea of what sort
of differentiation we can expect, as each has been a world unto itself
more or less, especially with Australia, Central Africa, many Pacific
Islands, and the Americas.
Many Pacific islands are useful in that they demonstrate both the
potential and the limits of flying creatures to fill evolutionary niches
free of other animals. Given a lack of competition from apes or other
intelligent creatures, birds were not able to develop any decent levels
of intelligence, mainly due to the limits of the mass fraction. The
weight restrictions of flight make large brains an evolutionary
disadvantage.
If we are talking about interacting with intelligent life, we have even
narrower specs to make extrapolations with. We can look at: Humans,
chimps, gorillas, porpoises and the other cetaceans (any other high
brain to body mass creatures?). So we can basically look at the
evolution of apes and cetaceans for clues as to _HOW_ they got where
they are. NOTE: I am _not_ saying that intelligent aliens will be apes
of cetaceans.
Given that apes and dolphins are capable of being taught to interpret
human language indicates that they are possibly not that far behind us
evolutionarily. However, what distinguishes us is that we INVENTED
language, and the tools we use. While some tool use is seen among apes
and dolphins, it is typically haphazard and quickly forgotten
occurences. There is not that much environmental pressure to continue to
use tools or develop more complex ones, as both species tend to have a
higher eat or be eaten ratio than the early humans did, so are not that
HUNGRY.
There is also another interesting datum: brain case to cervical cavity
ratio. Find animals that have large cervical cavities, or find the
environmental pressures that lead to the development of such large
cavities, and you can develop an idea of what sort of creatures are
capable of givng birth to big brained offspring. Even for ourselves, we
need the fetus to have a brain case that is not fully developed yet in
order to give birth, so it can squeeze through.
it turns out that a bipedal gait can acommodate a large cervical cavity
rather handily, supposedly much easier than quadrupeds, from a
mechanical standpoint, so we can infer that large cervical cavities
denote a relative evolutionary disadvantage for quadrupeds.
So now we know that an intelligent life form on another earthlike world
will most likely be a carbon based biped. We can also infer that due to
efficeincy/performance of optical/auditory arrangments, that the biped
will have two eyes, as well as two ears. Will it see in our visible
range? That depends on the spectra of the sun around which the planet
orbits, but there must not be a high level of UV, as UV breaks down DNA
rapidly and kills microorganisms, esp. the plankton. Given the spectra
that an oxygen/nitrogen atmosphere, with a protective EM radiation belt,
allows through, the peak output of a near sunlike star at planetary
surfaces will be in the visible and near visible range. Evolution will
take advantage of that, and eyes will develop sensitivity to whatever is
most efficient, i.e. the visible range. Since two eyes is the minimum
needed for stereoscopic vision, evolution willnot waste time with a
third eye, and likewise for ears.
This doesn't seem like that weird of an ET now does it?
-- TANSTAAFL!!!Michael Lorrey ------------------------------------------------------------ President retroman@tpk.net Northstar Technologies Agent Lorrey@ThePentagon.com Inventor of the Lorrey Drive Silo_1013@ThePentagon.com
Website: http://www.tpk.net/~retroman/ Now Featuring: My Own Nuclear Espionage Agency (MONEA) MIKEYMAS(tm): The New Internet Holiday Transhumans of New Hampshire (>HNH) ------------------------------------------------------------ Transhumanist, Inventor, Webmaster, Ski Guide, Entrepreneur, Artist, Outdoorsman, Libertarian, Arms Exporter-see below. ------------------------------------------------------------ #!/usr/local/bin/perl-0777---export-a-crypto-system-sig-RC4-3-lines-PERL @k=unpack('C*',pack('H*',shift));for(@t=@s=0..255){$y=($k[$_%@k]+$s[$x=$_ ]+$y)%256;&S}$x=$y=0;for(unpack('C*',<>)){$x++;$y=($s[$x%=256]+$y)%256; &S;print pack(C,$_^=$s[($s[$x]+$s[$y])%256])}sub S{@s[$x,$y]=@s[$y,$x]}