On Mon, May 30, 2005 at 11:46:08PM -0700, Norman Samish wrote:
> Dear Prof. Standish,
>
> Thanks for the quibbles, which sound reasonable. However, I'm going to
> stand my ground.
>
> You gave this reference about life's origins. (I found it at
> http://arxiv.org/PS_cache/astro-ph/pdf/0209/0209385.pdf)
>
> This article, as you point out, asserts "that the rapidity of biogenesis on
> Earth suggests that life is common in the Universe." This assertion is
> shown to be probably correct with some reasonable assumptions. One of the
> assumptions is that if life occurs here, it must also occur on other
> terrestrial planets.
This is not really assumed, but shown to be a more likely occurance
given the rapidity of biogenesis, than not.
However, the part that I have trouble with is figuring
> out exactly how that first living organism was created. ("Living" means it
> has the ability to take in energy from the environment and transform the
> energy for growth and reproduction.) "Living" requires a highly organized
> and complex mechanism - that humans, so far, have not been able to create.
> I can't imagine how such an organism could occur accidentally. I would call
> that first living organism a miraculous circumstance.
>
The origin of replicators has been demonstrated in a number of
computational system, the first, and probably most famous is Andy
Pargellis's Amoeba system. I'd have to do some digging, but I recall
having seen one or two other examples.
Origin of metabolic cellular structures seems to on the verge of being
demonstrated also in artificial media - there is a big push with Norm
Packard and Steen Rasmussen in Venice, of all places to do this in
chemical milieu. Digital examples might include Ono's artificial
chemistry model, and the original model of Autopoeiesis by Francisco Varela.
Taking these two steps together, origin of life is within reach. I
think this tells us life is perhaps not too hard, but complex
multicellular life on the other hand is.
> As for all of today's humans coming from 2000 breeders 70,000 years ago, you
> point out that this may merely mean that natural selection caused other,
> inferior, "Neanderthal" lines to disappear. This does not necessarily mean
> that some disaster had reduced the numbers of our breeding ancestors to
> 2,000, as I assumed.
>
> However, a natural disaster did occur approximately 70,000 years ago,
> according to
> http://www.olympus.net/personal/ptmaccon/pif/time_lines/time_lines_4.html
> This source says, "Largest volcanic eruption in 400 million years, producing
> 2500-3000 kilometers of ash, and 1 trillion tons of aerosols.
That would be larger than the Deccan Traps then, that occured during the
K-T transition approx 65 million years ago. I don't think so. That
volcano dumped around half a million cubic kilometres of lava on the
Earth according to
http://volcano.und.nodak.edu/vwdocs/volc_images/europe_west_asia/india/deccan.html.
According to other articles on the 'net, Mt Toba produced about 800
km^3 of material - a bit of a squib compared with the Deccan Traps.
Anyway, disredarding the initial hyperbole, it is interesting that
there was such a significant environmental impact at the time of this
genetic "bottleneck". We're not completely out of the woods though.
60-70,000 years ago corresponds the the accepted time for Homo Sapiens
to leave Africa - such an event is bound to have a genetic fingerprint
also (most of the genetic variation would remain within Africa for example).
Also I'm thinking to myself - how come I've never heard of Mt Toba
before? Is this some conspiracy on behalf of the Out of Africa
theorists, or is the Mt Toba theory somewhat of an exageration.
Anyway, cheers. Its always nice to hear a new angle on things.
--
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A/Prof Russell Standish Phone 8308 3119 (mobile)
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Received on Tue May 31 2005 - 03:29:57 PDT