On Sat, 24 Jan 1998 15:37:47 -0600, Glenn Morton wrote:
[...]
>GM>>We know that Homo erectus crossed the ocean 700,000 years ago and was
>>>on the island of Flores, Indonesia. It isn't far from there to Australia
>>>(indeed natural forest fires on Australia could have been seen from Timor
>>>an Island not far from Flores.).
>SJ>Australia...is often ravaged by lightning-lit fires...El-Nino effects can
>>cause a few years of droughts within otherwise wet periods...
>>
>>OTOH I have no problem with Homo erectus being in Australia 700,000
>>years ago.
GM>Nobody said that H. erectus was in Australia 700,000 years ago,
least of all I.
Nobody said *you* did say it. I said *I* have no problem with Homo
erectus being in Australia 700,000 years ago and lighting fires.
>SJ>The issue was whether the Jinmium art was the product of
>>H. erectus or H. sapiens. If it is 176,000 years old, then either:
>>a) it was H. erectus (which would make him more intelligent than
>>previously thought) or b) it was H. sapiens (which would make him
>>older than previously thought). Since there is no other evidence
>>elsewhere for either a) or b), and we know about El-Nino caused
>>fires in Australia, I prefer the latter explanation.
GM>Why no fires prior to 140,000 years ago. The entire pattern of soot in the
>air around Australia, recorded both in the Lake George Core and in oceanic
>cores changed significantly from the pattern seen in the earlier rocks.
As I said, this could have been caused by the beginnings of an
El-Nino cycle. Or it could have been caused by hominids. When there
is other positive evidence that hominids were in Australia 140,000
years ago, then I will accept the hominid-lit hypothesis.
But there is positive counter-evidence that large-scale destruction
of the Australian vegetation only occurred 10,000 years ago:
---------------------------------------------------------
The drying of a continent
HUMANS arriving in Australia 50 000 years ago may have drastically
altered its climate forever. Researchers said last week that
destruction of vegetation in the interior by early settlers could
have stopped monsoon rains from penetrating inland, turning much of
the continent's heartland into desert.
Australia's monsoons begin in December, when winds from Asia blow in
moist sea air, and last about three months. Geological records show
that in the past 150 000 years, monsoons everywhere were much wilder
and wetter at the end of an ice age, when the warmer weather swelled
the oceans.
However, there was one exception. When the last ice age thawed about
10 000 years ago, the Australian monsoons did not grow more severe.
By contrast, records of monsoons in Africa and Asia at that time show
that they became violent.
Gifford Miller of the University of Colorado in Boulder and his
colleagues wondered if it was mere coincidence that this unusual
dryness came after people arrived on Australian shores. "We knew
people were there," says Miller. "The question was why should that
be important?"
Modern Aborigines commonly use fire to clear land. If the first
Australians carried out the same practice, they may have
significantly reduced the plant cover in the interior. Plants absorb
water and then transpire it, so it can be absorbed by nearby
vegetation. With few plants in the interior, water would fail to
filter inland and much would evaporate away.
To find out if this process could have caused the climate change, the
researchers simulated the Australian monsoon using a computer climate
model. They tested how having an interior covered with desert or
vegetation would affect rainfall. To their surprise, vegetation
doubled the average amount of monsoon rains on the continent to about
4 millimetres per day. "If this is true, the bottom line is that
even with low technology, humans have changed climate on a
continental scale," he says.
"It's a very nice analysis and a surprising result," says Jenni
Evans, a meteorologist at Pennsylvania State University in University
Park. But she cautions that even the best climate models need to be
confirmed by direct evidence. Miller agrees and says there is
already geological evidence that the amount of burning did increase
fivefold after humans arrived. He intends to look for signs of a
shift in the type of vegetation growing in the interior at the same
time. Philip Cohen
(Cohen P., "The drying of a continent," New Scientist, Vol 156, No
2113/4, 20/27 December 1997, p6)
---------------------------------------------------------
>>>GM>Anyway, I will await the outcome before removing it...If the dates
>>>fail, you can be assured that I will remove it from my list. I
>>>have already removed Orce from the copy that went into the book.
>SJ>OK. But the study casts doubt on *all* the dates obtained by
>>thermoluminescence:...You might consider some such disclaimer in your list?
GM>Stephen, you haven't even looked at the list so you really don't know what
>you are talking about here.
Since you had not mentioned any changes, and in fact you were
defending its retention, I assumed it was still the same as when you
posted the list to the Reflector last July. In fact, you actually
said that you hadn't removed this from your list:
---------------------------------------------------------
Date: Sun, 18 Jan 1998 17:28:29 -0600
To: evolution@calvin.edu
From: grmorton@waymark.net (Glenn Morton)
Subject: Re: Doubts over spectacular Jinmium dates
[...]
GM>Anyway, I will await the outcome before removing it...If the dates
>fail, you can be assured that I will remove it from my list. I
>have already removed Orce from the copy that went into the book.
[...]
---------------------------------------------------------
But when I looked at your page http://www.isource.net/
~grmorton/chron.htm yesterday (28 Jan 97), I noticed that you have
deleted the Jinmium line. I also noticed that your visitors' counter
had been reset on the 18 January 98, which is the same day of your
above email saying you would not remove it from your list. Why did
you not simply say that you had deleted it, instead of leaving us all
with the mistaken impression that you weren't going to?
[...]
GM>I would also like to point out that you ignored the whole reason for the
>doubts about Thermoluminescence and the counter comments by those involved
>in the Jinmium dates.
I didn't "ignore" it. I have often been asked to keep my quotes to
the minimum, so since the article was three pages long, I posted the
main thrust of the article, evidenced by the title "Doubts Over
Spectacular Dates", and the first three paragraphs in full.
In any event, you do not practice what you preach. Your quotes are
invariably one-sided: witness your ignoring the evidence against
regional continuity in the Neandertal mtDNA sequence study. Also,
this very web page we are talking about is one-sided. You don't give
any counter evidence, or disclaimers about the unreliability of TL
dating, etc.
GM>Here is afuller account than your mere reporting that there are problems.
>Note the Jinmium teams responses to the criticisms.
GM>"While some electrons requre only a few minutes of sunlight to be
>bleached, or freed from their traps (the easy-to-bleach signal), others need
>hours or even days of ultraviolet light (the hard-to-bleach signal). If
>soil was blown into the site by the wind, the minerals probably did see
>enough light to be entirely bleached, says Huntley. But sediment deposited
>by a river or glacial outflow may not have been thoroughly bleached. As a
>result, the luminescence age it yields will be misleadingly old."~Ann
>Gibbons, "Doubts Over Spectacular Dates," Science 278(Oct 10, 1997), p.
>220-222, p. 221
This supports the general thrust of the article, that there are
doubts over the TL dates at Jinmium. On your argument I have ignored
evidence to support my case, the exact reverse is the case-I could
have posted *more* evidence in favour of my case.
GM>"'The trouble with the site is the date that was published based on the
>assumption that the quartz got fully bleached,' says Feathers, who is
>working to correct the problems with the OSL dating, which is better than TL
>at measuring the more reliable, easy-to-bleach signal. Hornyak, however, has
>said he is 'very confident' of the TL dates because repeated tests on the
>sediments have yielded the same result.'"
Again, this suppports my argument: "The...date that was published
based on the assumption that the quartz got fully bleached..." That
something else in the future (eg. OSL) may do a better job than TL,
goes without saying.
GM>Rubble Trouble
>
>"A problem of a different sort is undermining the TL dates on sediments
>at the Jinmium rock shelter; pebbles of crubly sandstone from the boulder
>wall or bedrock jumbled into the dated sediments. Because the rubble might
>not have been bleached at the same time as the sediments, it could have
>thrown off the dates.'Where there is rubble, there may be trouble,' jokes
>Richard 'Bert' roberts, a geochronologist at La Trobe University in
>Bundoora, Australia, who has dated many of the earliest sites of human
>occupation in Australia.
Same thing: "Because the rubble might not have been bleached at the
same time as the sediments, it could have thrown off the dates". I
would point out that Roberts is the physicist who actually did the TL
dating. I saw him on Australian TV at the time of the original
announcement and he was at that time very definite that the TL dating
was correct, therefore his second thoughts about it now are
significant.
GM>"Fullagar noted in his paper in Antiquity that although some of the
>layers he dated contained rubble, none was found in the layer with the
>oldest stone artifacts. Still, says Roberts, undetected grains from the
>wall of the rock shelter or from the bedrock below the sediment layer could
>have been mixed with the quartz that was dated. In a sample of 100 grains,
>he says, it would take just two 250,000-year-old flecks of quartz to give an
>overall date of 6000 years, even if the rest of the sample was just 1000
>years old."~Ann Gibbons, "Doubts Over Spectacular Dates," Science 278(Oct
>10, 1997),
>p. 220-222, p. 221
And again: "...undetected grains from the wall of the rock shelter
or from the bedrock below the sediment layer could have been mixed
with the quartz that was dated". Evidence for my case, which I could
have quoted.
GM>Now, I don't know how this will turn out. Jinmium may become much younger
>or it may be verified. As of this moment the date has not been overturned.
It hasn't even been established yet, so it doesn't need to be
overturned!
GM>It would be better in the future when you criticise something that you
>include as complete an account of the issues and the responses. As it was,
>all you did was say there was doubt. There is always doubt.
That's all I *was* saying-there was *doubt*. Your extra quotes did
not add anything to what I had already said. Indeed, you *supported*
what I said. Thanks.
God bless,
Steve
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Stephen E (Steve) Jones ,--_|\ sejones@ibm.net
3 Hawker Avenue / Oz \ Steve.Jones@health.wa.gov.au
Warwick 6024 ->*_,--\_/ Phone +61 8 9448 7439
Perth, West Australia v "Test everything." (1Thess 5:21)
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