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Re: Large animal extinctions caused by early man
cyberguy (cyberguy@IntNet.Net)
Sat, 06 Jul 1996 18:33:21 -0700
Scott Barboza wrote:
>
> On Thu, 4 Jul 1996, Richard C. Schmidt wrote:
>
> > In my view, you have two problems.
> > 1) Did, or did not the climatic changes that took place
> > during that time period cause the large scale die-out
> > of the larger animals?
> > 2) What was the cause of the climatic changes during
> > this time period?
> >
> > --------
> >
> > I feel that this entire discussion is confusing the two issues.
> > The fact is, the was a change in the climate 10-12,000 years ago.
> > We know this! The ice age ENDED!!!! Whether this was quick, in a
> > period of 1-3 years or less, or somewhat longer, is essentially
> > immaterial. IT HAPPENED!
> >
>
> Just a reminder to be careful of terminology here. The ice age is, of
> course, the Quarternary ice age and the Earth is currently in the midst of
> it. It did not end ~10,000 years ago, that age only marks the end of the
> last glacial advance of the Pleistocene. There have been numerous such
> advances and retreats throughout the Pleistocene epoch. The 18,000-10,000
> b.p. advance was only the latest. IMO the geologic time scale is a little
> misleading. The Holocene is taken to begin about the time of the last
> glacial retreat. However, what is different about this retreat from the
> numerous retreats throughout the Pleistocene? I think that having a
> different epoch for the last 10,000 yrs overemphasizes the last retreat
> too much and often leads to confusion about the present ice age.
>
> > Did this change in climate cause a die-off? i'm not sure, nor
> > is anyone else. But, these climatic changes ussually change
> > the habitate of the areas affected, and thus, the survivalability
> > of the inhabitants. Humans are, generally, better able to cope with
> > this than animals, and the large animals, have, traditionally,
> > been the ones that suffer the most! Humans had not done the
> > job in the previous 100,000 years in Eur-Asia, so there is no
> > reason to suspect that humans, in a relatively short time would
> > suddenly do so now. They may have helpped push the marginally
> > able over the edge though.
> >
>
> I'm not an paleontologist, but the question that comes immediately to my
> mind is this. Why did all of these extinctions happen only after the last
> ice advance to species which wheathered all of the previous advances and
> retreats without any problem at all? In the context of the Quarternary
> ice age, what is the evidence that large animals "traditionally" suffered
> except at the end of the Pleistocene. I think that the answer must be
> that there was _something_ different (presence of humans?) about this
> latest retreat. I also think that, in general, the fossil record is
> incredibly biased in favor of large animals. So, it shouldn't be a
> suprise that we know of the extinctions of large animals the best as a
> statistical artifact alone.
>
> > As to why the ice age ended, the climate changed, we, at present,
> > have NO DIRECT evidence! We open to suthe great guessing game.
> > A moderately sized metorite impact in the middle of the Atlantic
> > is as good a reason as any I've seen so far.If anyone else
> > has a theory, please put them forward. I've seen writings
> > about the effects, BUT this is the first guess as to the
> > cause!!!!!!!!!!!
> >
> > ~~ Richard C. Schmidt
> >
>
> Didn't Milutin Milankovitch propose a celestial mechanics mechanism in the
> late 1920's or early 1930's? I assume that most readers here are
> familiar with Milankovitch cycles. If not, they are explained in any
> introductory geology text. Many geologists still accept this explanation
> for glacial advances and retreats during an ice age. However, there have
> been many ice ages and the mechanism for what initiates one is a bit more
> enigmatic. The oldest known is the Precambrian ice age which occured
> about 2.2 ga. There was probably another during the Paleozoic (~500 ma)
> and an extensive one during the Permian (250-300ma). The Quarternary ice
> age began about 1.6 ma. There have been many mechanisms that have been
> proposed - in truth, probably all of the factors played a role. The
> relative rarity if ice ages suggests that some combination of factors must
> be at work. Some of the proposed mechanisms for the initiation of the
> Quarternary ice age:
>
> 1) Positioning of Antarctica over the pole (~50ma)
> 2) Separation of the South America land bridge from Antarctica. This
> allowed circum-polar currents to flow and is probably responsible for the
> flow of Anarctic Bottom Water which began shortly thereafter.
> 3) Iceland volcanism blocked cold water from the vicinity of the North
> Pole from mixing with equatorial waters in the Gulf Stream in the
> Atlantic.
> 4) Subduction-related volcanism along the Aleutian arc blocked cold water
> from the Bering Sea from mixing with equatorial waters in the Pacific.
>
> I favor a combination of these factors (and probably some that I have
> ommitted). I have heared 1) and 2) put forward the most often and I
> assume that there is some sort of consensus about their role.
>
> Scott Barboza
> University of Washington
> Department of Geological Sciences==================================
Correct me if I am in error here, but isn't it good science to compare
similar/identical events and make inferences based on observable cause
effect relations for areas where direct observation is not possible?
I often chuckle that there is a missed bet (albiet heretical) in such
debates as this. By actual present time observation, the biggest single
cause for extinctions is MAN (a dominent species). What makes anyone
think that this would be the first time people have been pigs and killed
off everything in sight and fowled the environment? There have been a
lot of mass extinctions. And an ice age is a matter of where you live
in part. If the world flips about on its axis or a tech plate slides
into the wrong place, bingo you have a place with evidence for
glaciation. By the way, in good old Science News I think it was last
year they had an article that indicated that the glacial epoch (last)
came on over only 20 years. Man has managed to screw up the planet
going from coal to HBOMBS and liquid hydrogen roman candle "space ships"
in about 200 years. And on this planet right now there are people who
STILL are in the stone age. Sooo - just for the sake of heretical
thought, how many times in several billion years could you find 10000
years to go from savage to global screw up? This is taking an OBSERVABLE
cause effect only. (and don't say it couldn't happen - if you dig down
under the sand in the middle east under 6 or 9 mud hut 'civilizations'
you find green glass, also in Gobi, in Australia, Lybia, etc. All is
NOT as it seems in junior high school or establishment history. You
should talk to the oil field workers some time about some of the strange
things they dig up. How many observations are right there to be made or
have been made and thrown out because they don't fit some theory. Heck,
check out the Indian legends and folk lore about their happy hunting
grounds. Can't you just see people killing off the big cats and other
large animals - look what we did to the whales last century!! why is
that so hard to believe that people have been people for a LONG time.
Like I said, heretical, but food for thought.
CYBERGUY
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