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. 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.
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. Cloud was
more than 34 kilometers high. Ash covers India between 1 and 6 meters deep.
(May have started folllowing cooling period). 6 year period during which
the largest amount of volcanic sulphur was deposited in the past 110,000
years, followed by 1000 years of the lowest ice core oxygen isotope ratios,
temperatures were colder than during the Last Glacial Maximum at 18 - 21,000
years ago. Sea level was 160 feet below current. Global temperature drops
average of 21 degrees. Volcanic Winter lasted about six years. It was
followed by 1,000 years of the coldest Ice Age on record. Warming begins
again 1,000 years later. Believed that the 1% human genetic variation stems
from this time. No other species shows such a small variation. Genetic
evidence suggests only 1,000 adults survived world wide. May be event which
caused rise in modern racial differences - Professor Stanley Ambrose of the
University of Illinois." This article suggests that near-extinction of
humans did occur.
Norman Samish
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Minor quibbles, which don't actually detract from your argument:
On Mon, May 30, 2005 at 01:19:28PM -0700, Norman Samish wrote:
> 1) How did life originate if not through a miraculous circumstance? In
> other branches of the multiverse, perhaps most of them, there is no life.
There is evidence that life might arise fairly easily, given the right
conditions. This is the so-called "early appearance of life
argument". See arXiv:astro-ph/0209385.
> 2) An article at
> http://news-service.stanford.edu/news/2003/may28/humans-528.html
> suggests that all of earth's present human inhabitants originated from
> about
> 2,000 breeders, about 70,000 years ago. Humans were then very close to
> extinction. In many other branches of the multiverse extinction did, in
> fact, occur.
Endangerment of a species does not follow from a genetic
"bottleneck". Consider a beneficial mutation arising 70,000 years ago,
and rapidly increasing to 100% fixation within the human
population. The genetic data would point to us all being descended
from a single "Adam" or "Eve" at the time, and the number of
individuals whose descendants ultimately breed with Adam or Eve's
descendents. All other germ lines are eliminated from the population
by natural selection. Thus a genetic bottleneck. However, the breeding
population may have been any number - eg 1 million, hardly an
endangered species.
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Received on Tue May 31 2005 - 02:49:05 PDT