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Author | Topic: How did the Aborigines get to Australia? | |||||||||||||||||||||||||||||||||||||||||
Granny Magda Member Posts: 2462 From: UK Joined: Member Rating: 4.0
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Hi Zen Deist,
There was no land bridge between Asia and Australia. No, not directly, but that wasn't quite what I had in mind when I first brought this up. There was no direct link between what we now call Asia and what we now call Australia, but there was, at one point, an more-or-less overland connection, via Gondwana. The marsupials took the looooong way around. What matters for the purpose of this discussion is that the Marsupials appear to have originated in Laurasia, possibly in what is now China. They spread into Gondwana via what is now North America. They then moved into South America and then Antarctica and eventually Australia. As those three continents drifted apart, their marsupial populations became isolated from one another. The following image, based on marsupial genome research, gives some idea of the route taken;
The only part of this marathon journey that wasn't directly overland was the bit between North and South America, but this was only a very short distance, with an archipelago of islands linking the two, so it's not a stretch to imagine how this might have happened, most likely via small-scale rafting. This image shows how the modern continents made up Gondwana (along with some of the fossils that provide us with evidence for their positions).
As Antarctica moved South, the marsupials died out, because it became too cold. They died out in Eurasia too, likely from competition with placental mammals. In South America and Australasia though, they persisted. Most of the South American marsupials died out when the land bridge formed between the Americas; this also explains how the marsupial Virginia Possum got where it did. But the Australasian species, with no pesky placentals to compete with, thrived and diverged. These ancestral populations eventually evolved into the wallabies and kangaroos that have been perplexing Portillo. The ironic thing about this epic migration of land and species is that Australia has now moved far enough north that the marsupials are right on the edge of Asia; very nearly back where they began. I know that you know this already, I just want to make the position clear for other readers. Mutate and Survive Edited by Granny Magda, : No reason given. Edited by Granny Magda, : No reason given. Edited by Granny Magda, : No reason given.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi Granny Magda,
Thanks for adding further to the story of Australia.
... But the Australasian species, with no pesky placentals to compete with, thrived and diverged. These ancestral populations eventually evolved into the wallabies and kangaroos that have been perplexing Portillo. The ironic thing about this epic migration of land and species is that Australia has now moved far enough north that the marsupials are right on the edge of Asia; very nearly back where they began. I know that you know this already, I just want to make the position clear for other readers. The only footnote I would add, is that the modern marsupials on Australia all evolved after the separation, and isolation, of Australia. This certainly does not answer the question of how koalas, for example, could get from a central ark landing site to Australia. Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
Or from Australia to a Middle East Ark launching site so they could be on board to get dropped off after the Flud.
Anyone so limited that they can only spell a word one way is severely handicapped!
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foreveryoung Member (Idle past 582 days) Posts: 921 Joined: |
Science answer: they evolved there. Creationist answer: ? (careful - I've heard some doozies)
They evolved from a set of triassic mammals that lived on gondwana. The triassic mammals that remained on land that became asia evolved into the mammals that we see today. The triassic mammals that remained on land that became australia evolved into the marsupials that we see today.
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Dr Adequate Member (Idle past 284 days) Posts: 16113 Joined:
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ZD writes: I beg to differ. GM writes: There was no direct link between what we now call Asia and what we now call Australia, but there was, at one point, an more-or-less overland connection, via Gondwana. The marsupials took the looooong way around. I stand corrected, I shouldn't have agreed that there was a land bridge, just an overland route. Thanks.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi jar,
Or from Australia to a Middle East Ark launching site so they could be on board to get dropped off after the Flud. Could be, but the typical creationist explanation is (a) that pre-flood geology differed and/or (b) the animals came to Noah so he didn't have to round them up. It is much more difficult to argue about leaving the ark being special conditions. Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
Of course they can make up any crap they want to, but the fact is that there is lots of evidence of 'roos in Australia before there were people there and NO evidence of 'roos in the Middle East until there were Zoos.
Now if the 'roos came to the Ark it goes back to the questions I asked back in Message 8. Did Noah build a boat and go get them? Did the 'roos hop on water to come to the Middle East? Maybe the God in the Biblical Flood Myths parted the Indian Ocean so that two pair (or seven pair) of 'roos could hop over to Thailand and up through Burma and India and Pakistan and Iran and Iraq?Anyone so limited that they can only spell a word one way is severely handicapped!
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi foreveryoung, and welcome to the fray
They evolved from a set of triassic mammals that lived on gondwana. The triassic mammals that remained on land that became asia evolved into the mammals that we see today. The triassic mammals that remained on land that became australia evolved into the marsupials that we see today. And North America and South America and Africa ... That would be the scientific explanation, not a creationist explanation.
Message 330, New theory about evolution between creationism and evolution.: I am YEC but not like any that I have found so far on this forum. I have a wide range of possible ages for the earth but they are no older than a million years and no younger than 150,000 years. I believe in a global "flood", but I do not restrict its activity to massive amounts of rainfall as we see the phenomena today. I believe the great "flood" coincided with the Late Heavy Bombardment, and that the great flood of noah coincides with that periods characteristic total coverage of water. I know that was 3.9 billion years ago measured radiometrically, but I believe it happened much later than that due to accelerated radioactive decay. The problem for you is that this doesn't make the scientific explanation work for your brand of creationism (which sounds a lot more like old earth creationism or gap creationism than YEC). If you want to argue about the age of the earth, then I suggest you read and reply to Age Correlations and An Old Earth, Version 2 No 1 -- note that the issue of interest is the correlations between the various methods. Science is consistent and there are a lot of cross-correlations between a number of different sciences. If you think "... due to accelerated radioactive decay" is a viable argument, then you haven't really looked at the new problems you create that now need to be explained. See Are Uranium Halos the best evidence of (a) an old earth AND (b) constant physics?:
quote: Rapid decay means no uranium halos, but uranium halos are common, therefore no rapic decay. There are other problems, but uranium halos are objective empirical evidence that falsifies any hypothesis of rapid decay. Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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Coyote Member (Idle past 2106 days) Posts: 6117 Joined: |
Fast decay kind of cooks the earth too.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi Coyote,
Fast decay kind of cooks the earth too. Yep. It also means that there would have been a large number of spontaneous natural reactors wherever uranium and other fissionable isotopes were found in the concentrations seen in the earth today: none of these deposits should exist, because they should have all gone through the melt-down sequence seen at Oklo: http://oklo.curtin.edu.au/
quote: With more rapid decay, the critical mass would be smaller, and there would be many such reactions occurring with smaller concentrations of fissionable materials. Curiously, the only evidence we have for such reactions is where there was sufficient fissionable mass to cause reactions the same as what we see in the world today. Therefore rapid decay did not occur. And, because of the byproducts of radioactive decay, and their relative amounts, we can date the Oklo reactors: http://oklo.curtin.edu.au/when.cfm
quote: That's 2 billion years old. Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi again jar,
We are essentially arguing passed each other.
Of course they can make up any crap they want to, but the fact is that there is lots of evidence of 'roos in Australia before there were people there and NO evidence of 'roos in the Middle East until there were Zoos. Now if the 'roos came to the Ark it goes back to the questions I asked back in Message 8. Surely you are familiar with ICANT's gondwanaland pre-flood concept? No water\oceans to cross, plus the flood wipes out evidenceof travel to the ark site. Creationists can, have, and will shrug off these questions. The problem that can't be shrugged off is how they get to their current locations from the ark. And if the fossil evidence is from the gondwanaland time, then how do the species get to the specific land masses that have their ancestral fossils? Most curious. Enjoy.by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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NoNukes Inactive Member |
It also means that there would have been a large number of spontaneous natural reactors wherever uranium and other fissionable isotopes were found in the concentrations seen in the earth today: I don't think this is correct. Your post seems to confuse decay with fission. Speeding up decay does not necessarily mean creating a critical or super-critical natural reactor. In fact, producing a self sustaining fission reaction does not follow from having sped up nuclear processes. What is required is that each neutrons produced by a fission reaction on average produce at least one new neutron from fission. This depends more on the physical arrangement and enrichment of the fissile material, and to a first order is independent of the rate at which absorbing a neutron causes an atom to split.Under a government which imprisons any unjustly, the true place for a just man is also in prison. The proper place to-day, the only place which Massachusetts has provided for her freer and less desponding spirits, is in her prisons, to be put out and locked out of the State by her own act, as they have already put themselves out by their principles. Thoreau: Civil Disobedience (1846)
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi NoNukes,
Sorry to have confused you.
I don't think this is correct. Sadly, for you, opinion is incapable of altering reality.
Your post seems to confuse decay with fission. Speeding up decay does not necessarily mean creating a critical or super-critical natural reactor. Curiously, critical mass is defined by the number of decay events within a given volume of radioactive material. Critical mass - Wikipedia
quote: What is required is that each neutrons produced by a fission reaction on average produce at least one new neutron from fission. This depends more on the physical arrangement and enrichment of the fissile material, and to a first order is independent of the rate at which absorbing a neutron causes an atom to split. Enrichment means increasing the density of decaying material. Enriched uranium - Wikipedia
quote: In other words the density of 235U in the lowest category of enriched material used in reactors is a little more than double what it is in nature. If your double the rate of radioactive decay, then that produces the same number of decay events in a given time period that would occur in twice the density of current fissionable isotopes compressed into half the current volume. It would be the same as enriching available ore to have twice the number of decay events. Result: a two-fold effective density of radioactive material. Uranium ore with this density of fissionable material occurs in the world today. As such ore did not cause fission events similar to Oklo, then such doubling did not occur. Curiously, to achieve anything close to a YEC model age, doubling the rate of radioactive decay is terribly insufficient: it would only mean reducing the age of the earth from 4.55 billion years to 2. 27 billion years. Enjoy Edited by Zen Deist, : clrtyby our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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NoNukes Inactive Member
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Zen Deist writes: Curiously, critical mass is defined by the number of decay events within a given volume of radioactive material. Really. So why does your quote lists the variables that I mentioned? It does not support your position at all.
quote: Enrichment and geometry. Just as I said. The purpose of the neutron reflective material, which I did not mention, is to return neutrons that escape the mass back to the fissile material. I would lump that in with geometry. Again, this supports my position.
Enrichment means increasing the density of decaying material. That is not right. And it is not what your reference says. First, fission is not decay. Fission in a critical or super-critical reactor is generated primarily by the absorption of thermal (slow) neutrons by fissile material. Only the tiniest amount of neutrons are produced by spontaneous fission, which might be considered similar to decay. As long as the spontaneous fission rate is non-zero, and the geometry and enrichment are correct, then induced fission can occur and will dominate. Enrichment means the ratio of fissile to non-fissile material. As an analogy, consider that spontaneous fission, which can be likened to decay and might increase when the decay rate increases, is only the fuse for the chain reaction. It doesn't matter much how bright is the match that lights the fuse. Here is how a chain reaction is produced in a natural or man made reactor. Some amount of spontaneous fission occurs, spontaneously producing neutrons fast neutrons. Each fission of U235, for example, produces 2.4+ fast neutrons. But only some of those neutrons in turn are slowed and cause fission. Depending on geometry, enrichment, the amount of neutron absorbing materials like carbon and hafnium, thermalizing material, and some other variables, only some of those neutrons get slowed down to thermal speed, and then engage new U235 nuclei causing fission. For at more complete description of the neutron life cycle see the wikipedia article on the six factor formula. Six factor formula - Wikipedia As long as about 42 percent or more of those 2.4+ neutrons in turn produce induced fissions of U235, then an upward ramping chain reaction is produced. It scarcely matters exactly what the the reaction rate of spontaneous fission rate is, because of the multiplying effect caused by the chain reaction, at least approximately so. What does matter is how many neutrons escape or or absorbed without producing fission. And that depends primarily on geometry and enrichment. Not on the decay rate. ABE: by "how many", I mean how many escape or are absorbed as a percentage of those neutrons produced. Doubling the spontaneously produced neutrons doubles the number of neutrons that escape, thus maintaining a non-critical neutron life cycle. Edited by NoNukes, : No reason given.Under a government which imprisons any unjustly, the true place for a just man is also in prison. The proper place to-day, the only place which Massachusetts has provided for her freer and less desponding spirits, is in her prisons, to be put out and locked out of the State by her own act, as they have already put themselves out by their principles. Thoreau: Civil Disobedience (1846)
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saab93f Member (Idle past 1394 days) Posts: 265 From: Finland Joined:
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A local creationist suggested (in all honesty I think) that God used whirlwinds and angels to carry the animals from one place to another. Apparently that applied in both collecting and then depositing the creatures. He even tried to make jetwinds suit his way of thinking.
Even though I am taught to be polite and respect everyone regardless of their agenda, it is extremely difficult to show any to cretins. At best they are mislead and delusional and at worst lying maniacs. Not much positivity there.
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