Viti

As little as I know about it, I will say that viruses and extremophiles are two things that made be stop doubting abiogenesis.

tronvillain

Actually, it's not all that interesting - they have no metabolism to disrupt, drastically reducing the possible avenues of attack.

Bill

Of course, the great "chicken and egg" debate with viruses is that, if a virus must hijack a living cell in order to replicate itself, then viruses cannot have evolved before there were living cells available for hijacking. Q.E.D.

So, while viruses are an interesting part of the spectrum from life to non-life today, I don't see them as a stepping stone on the road to abiogenesis.

But what sort of thing, that is still around today, would be just such a stepping stone?

== Bill

Viti

Bill...as I said extremophiles seem a highly unlikely form of life...yet living they are. I don't much about them but what I have found on the web...anyone else have any info?

tronvillain

Bill:
Perhaps no sort of thing that is still around today would be such a stepping stone. Is there any reason to expect one to?

Bill

In my humble opinion, no. But that seems to be one of the assumptions that people naturally tend to make: that some remanents of the original organism have to exist SOMEWHERE here on Earth, today. Those people don't seem to understand that the combined probability factor of several 90+% extinction events makes it pretty damn unlikely for anything to have survived "from the beginning." There are those changes in the environment that happen from time-to-time, too.

== Bill

Bill

I saw the IMAX movie on the two ladies who were going around the world collecting extremophiles from rock caves, ice caves, fresh/salt inversion layers, and the like. Drug companies seem to be highly interested in extremeophiles as a potential source of new and exotic drugs.

My personal guess is that extremophiles simply adapt to their environment, just like any other organism. And when the environment changes, the survivors are, by necessity, adapted to the changed environment. Gradually, you obtain an organism that is adapted to the most horrid of conditions......

== Bill

Ron Garrett

For me it was the fact that Strom Thurmond fathered his youngest son in 1976. Proof positive that dead things can give rise to the living. Or does that just prove that dead things can still rise?

ecco

Quote from Lannergard:

RE: 1-4. I agree with points 1-4 using OR rather than [i]AND[/] as a connector. A rock is definitely not alive. It cannot grow or replicate or purposely transfer energy or respond to stimuli nor ensure self-preservation. It exhibits none of these qualities.

Then, of course, I run into the problem of crystals. Hmmm.

Most of the living cells in my body are surrounded by other living cells. These cells lack your fifth characteristic. Are you saying I am comprised of dead cells? There are those who have made that statement about my brain cells, but my whole body???

I did a little net surfing myself to see what I could find.

The answer I liked best (It depends / We don’t know) was found at: <a href="http://www.ibiblio.org/jstrout/uploading/potter_life.html" target="_blank">http://www.ibiblio.org/jstrout/uploading/potter_life.html</a>

Also good was: <a href="http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_chem_1.html" target="_blank">http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_chem_1.html</a>

[ January 28, 2002: Message edited by: ecco ]</p>

Quetzal

Bill:

re: viruses as stepping stones. Although not strictly accurate as far as modern viruses (virii?) go - which are superbly adapted parasitic whatevers - if you accept the RNA World hypothesis, something very like a virus (simple rRNA strand, maybe surrounded by a rRNA-catalyzed protein or lipid sheath) is likely to have been one of the first organic replicators. It's not really that great a step to archaea, then from there to more complex cells. Modern extremophils, especially the thermophils, may likely have been similar to the first living cells, since undersea thermal vents provide lots of free energy to work with, and would be a pretty good place for life to begin.

Is a virus "alive"? Beats me. But I'm not sure the question "what is life" actually has a meaningful answer...

My 12.5 kopeks.