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From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.sf-lovers
Subject: Re: Space Is Clean
Message-ID: <909@psivax.UUCP>
Date: Wed, 18-Dec-85 13:14:19 EST
Article-I.D.: psivax.909
Posted: Wed Dec 18 13:14:19 1985
Date-Received: Sat, 21-Dec-85 19:01:24 EST
References: <602@caip.RUTGERS.EDU>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 73

In article <602@caip.RUTGERS.EDU> Piersol.PASA@Xerox.ARPA writes:
>From: Kurt <Piersol.pasa@Xerox.ARPA>
>
>>        There is a fallacy here, the assumption that the set of
>>possible forms taken by living things is unrestricted. In fact the
>>structure of living things is controlled by "natural laws" in about
>>the same way as the interactions of subatomic particles are.
>
>Aren't you making some rather sweeping assumptions about what sort of
>environments life can arise in?  I think I agree that life forms from
>essentially terran environments are likely to bear great similarities to
>terran life, and may even have very close DNA analogues.  However,
>that's about as far as I'm willing to go.

	Not really assumptions, more like probability analyses. I have
actually spent quite a bit of time studying these issues. The problem
is that by the time you have covered all terran environments that
contain life you have covered most environments where life is even
possible, at least as far as I can determine on the basis of organic
and general chemistry.

>Consider the sulfur consuming life forms found in deep oceans, which
>follow a totally new and previously unsuspected food chain based not on
>solar but chemical energy (oh, solar way back, but fundamentally
>different in that no photosynthesizing plants are part of the chain).

	What previously unsuspected food chain? That type of food
chain has *long* been considered to have been the original food chain
on the Earth, before the invention of photosynthesis a billion years
or so *after* the first living thing. The only surprise here is that
this type of food chain *still* exists now. Besides, this is *still* a
terran life environment, with terran life forms, so my thesis is still
valid, life on other planets will tend to resemble life in *some*
environment or from *some* geological era on Earth. (Note that is
*resemble*, not 'be identical with')

>Surely, with the limited set of environmental conditions we have been
>able to examine, we are in no position to make any claims about what
>life forms are likely to arise or become sentient.

	We can however evaluate the conditions necessary for various
types of developement. Thus sentience requires manipulative ability,
and, except in high energy environments, animals(i.e. phagotrophic
organisms) require *motility*.
>
>With this lack of information, I'd also be unwilling to generalize about
>any chance of overlap.  One can imagine a number of possible cases where
>humans and aliens have no overlap at all except a need survive and to
>reproduce.

	Given the enormous variety of environments on Earth, and the
enormous variation that has occurred through time, we have a lot
*more* information than you think. Yes, there might be some life forms
on other planets that have no real equivalent on Earth(and vice
versa), but there will be many more life forms on any planet that do
correspond more or less with Earth life forms. That is other planets
will show an equally large range of life forms as Earth, with a rather
large area of overlap.

>There are also serious questions about whether the human
>world-view may have any resemblance to one developed by alien sentients,
>particularly those with vastly different body structures.
> 
	Here you may have a point, though considering the vast
differences in world-view among different Earth-human cultures I
suspect that humans could at least *learn* the alien's world-view, and
they could probably learn ours.
-- 

				Sarima (Stanley Friesen)

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