1 July 2013

ANU boffins say it wasn't climate change that did for the megafauna

| johnboy
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ANU is having a go at debunking the idea that the mass extinction of large animals in the Australian mainland 50,000 years ago was caused by random climate variations.

Humans with pointy sticks and hunting fires come sharply into the frame although the boffins don’t go that far.

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justin heywood said :

One journal article doth not a scientific fact make – and on this topic there hundreds of articles, mostly with a different point of view than that expressed by Field and Wroe.

There well may be “hundreds” of articles on the subject but that doesn’t change the fact that the archaeological record is so sparse as to be unable to differentiate between the competing hypothesis. I wouldn’t have thought it would be too outrageous to suggest that we just don’t know and probably will never know.

Thumper said :

Tiger Quolls the size of action buses!

Look at the Zygomaturus trilobus. That is Latin for ‘big as three ACTION buses, but not as old or orange.’

Gungahlin Al said :

thebrownstreak69 said :

We’re talking about wooley mammoths here, right?

No Mammoths were restricted to the Siberia/North America areas. When referring to Australian megafauna, scientists are talking about all the bigger animals – including current ones, but mostly talking about the extinct ones. Picture a 3m 2000kg wombat, a 500kg emu and a 7m goanna! Not actually those animals but they resembled the current species, just huge.

Pretty good summary of it all in Wikipedia: http://en.wikipedia.org/wiki/Australian_megafauna

Tiger Quolls the size of action buses!

Gungahlin Al2:20 pm 03 Jul 13

thebrownstreak69 said :

We’re talking about wooley mammoths here, right?

No Mammoths were restricted to the Siberia/North America areas. When referring to Australian megafauna, scientists are talking about all the bigger animals – including current ones, but mostly talking about the extinct ones. Picture a 3m 2000kg wombat, a 500kg emu and a 7m goanna! Not actually those animals but they resembled the current species, just huge.

Pretty good summary of it all in Wikipedia: http://en.wikipedia.org/wiki/Australian_megafauna

justin heywood said :

howeph said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

Roundhead89, you must be smarter than me, because I can’t see any climate change myth crashing down.

Please explain.

In fact, a change in the climate is one of the competing theories in explaining the disappearance of the megafauna. A very interesting topic, but a bit of a perfect storm of competing scientific theories unfortunately complicated by politics.

What do you mean by ‘complicated by politics’?

Whenever this topic comes up, respectful discourse between scientists degenerates into a childish sand-pit of denigration, ad homs, etc. There are only a few cases where this happens, usually with some underlying financial/political/or ideological contention.

I’m wondering what that political complication is in this case(??)

justin heywood7:48 pm 02 Jul 13

davo101 said :

CraigT said :

The problem with stating the obvious, “Humans arrives and hunted the megafauna to extinction”, is that it goes against the noble savage fantasy of the Aboriginals as “caretakers of the land” and similar rubbish such as trying to paint fire stick hunting as a land management technique instead of the destructive vandalism that it was.

No the problem is that there is not enough evidence to state this. To quote Field and Wroe (2012):

In our view the question remains wide open. Arguments for either a human- or climate- driven process remain based on major and currently untested assumptions. Notably, acceptance of a human-driven event assumes that the PGM and LGM were no more severe than the glacial maxima that preceded them and that a lack of evidence for most now extinct species post-PGM is a sampling artefact. Arguments for a climate-driven process may assume the reverse. Neither position is strongly supported by hard evidence at present, but it is increasingly clear that the climate was deteriorating at the time humans are thought to have arrived. The unknown number of megafaunal species present at human arrival faced possible direct or indirect influences from humans and increasingly arid and variable climate. Even with the advantage of far better resolved palaeoclimatic data and extinction chronologies than are presently available, it would be difficult to quantify the respective roles of either factor robustly.

One journal article doth not a scientific fact make – and on this topic there hundreds of articles, mostly with a different point of view than that expressed by Field and Wroe.

BimboGeek said :

I thought the collossal squid is bigger than a blue whale? I find normal tentacles terrifying, collossal ones can stay in the abyss!!

Just to give you a size comparison the blue whale can weigh up to 170 tonnes

http://www.heraldsun.com.au/leader/west/enormous-btriple-and-bdouble-trucks-may-soon-be-on-yarraville-streets/story-fngnvmj7-1226665461864

Spitfire3 said :

BimboGeek said :

I thought the collossal squid is bigger than a blue whale?

Nowhere near as big as blue whales.

Katy, we may need a skysquid for the next bash.

Beware the mighty Kraken!

BimboGeek said :

I thought the collossal squid is bigger than a blue whale?

Nowhere near as big as blue whales.

Katy, we may need a skysquid for the next bash.

BimboGeek said :

I thought the collossal squid is bigger than a blue whale? I find normal tentacles terrifying, collossal ones can stay in the abyss!!

Mmmmmm. Colossal salt and pepper squid!

So, would you describe Godzilla as megafauna, or ultramegafauna, or motherf*ckafauna, or gigafauna?

I thought the collossal squid is bigger than a blue whale? I find normal tentacles terrifying, collossal ones can stay in the abyss!!

You really must stop watching those japanese cartoons…

CraigT said :

The problem with stating the obvious, “Humans arrives and hunted the megafauna to extinction”, is that it goes against the noble savage fantasy of the Aboriginals as “caretakers of the land” and similar rubbish such as trying to paint fire stick hunting as a land management technique instead of the destructive vandalism that it was.

No the problem is that there is not enough evidence to state this. To quote Field and Wroe (2012):

In our view the question remains wide open. Arguments for either a human- or climate- driven process remain based on major and currently untested assumptions. Notably, acceptance of a human-driven event assumes that the PGM and LGM were no more severe than the glacial maxima that preceded them and that a lack of evidence for most now extinct species post-PGM is a sampling artefact. Arguments for a climate-driven process may assume the reverse. Neither position is strongly supported by hard evidence at present, but it is increasingly clear that the climate was deteriorating at the time humans are thought to have arrived. The unknown number of megafaunal species present at human arrival faced possible direct or indirect influences from humans and increasingly arid and variable climate. Even with the advantage of far better resolved palaeoclimatic data and extinction chronologies than are presently available, it would be difficult to quantify the respective roles of either factor robustly.

CraigT said :

The problem with stating the obvious, “Humans arrives and hunted the Megafauna to extinction”, is that it goes against the noble savage fantasy of the aboriginals as “caretakers of the land” and similar rubbish such as trying to paint firestick hunting as a land management technique instead of the destructive vandalism that it was.

True indeed.

Mind you, there’s a subtle, though important, difference between destructive vandalism for the purpose of feeding yourself in ignorance of the consequences, and destructive vandalism for increased profits in the full and certain knowledge of the consequences.

justin heywood said :

There is a LOT of evidence pointing to a general extinction of megafauna at about the same time as the arrival of humans. These species had survived even ice ages before, but disappeared at a time when, relatively speaking, the climate was not changing rapidly.
This is certainly circumstantial evidence, but it would be a remarkable coincidence if humans were not the cause. They most certainly were the cause of mass extinctions on many other islands.

…as they are the cause of the current mass-extinction event that is in progress.

The problem with stating the obvious, “Humans arrives and hunted the Megafauna to extinction”, is that it goes against the noble savage fantasy of the aboriginals as “caretakers of the land” and similar rubbish such as trying to paint firestick hunting as a land management technique instead of the destructive vandalism that it was.

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

Yeah, because we all know what really killed megafauna – it was feminists and their agenda….

Might have been Costco!

poetix said :

DrKoresh said :

johnboy said :

Don’t tell the elephants

That’s why I qualified my statement with the word “most”, smarty-pants :p

Whales are quite large, too.

Indeed and many of us would be aware that the Blue Whale is the largest creature that has ever existed..

DrKoresh said :

johnboy said :

Don’t tell the elephants

That’s why I qualified my statement with the word “most”, smarty-pants :p

Whales are quite large, too.

From Wikipedia:

New evidence based on accurate optically stimulated luminescence and uranium-thorium dating of megafaunal remains suggests that humans were the ultimate cause of the extinction of megafauna in Australia.[4] The dates derived show that all forms of megafauna on the Australian mainland became extinct in the same rapid timeframe — approximately 46,000 years ago[5] — the period of time in which humans first arrived in Australia. Analysis of oxygen and carbon isotopes from teeth of megafauna indicate the regional climates at the time of extinction were similar to arid regional climates of today, and that the megafauna were well adapted to arid climates.[4] The dates derived have been interpreted as suggesting that the main mechanism for extinction was human burning of a landscape that was then much less fire-adapted; oxygen and carbon isotopes of teeth indicate sudden, drastic, non-climate-related changes in vegetation and in the diet of surviving marsupial species. However, humans appear to have rapidly eliminated the megafauna of Tasmania about 41,000 years ago (following formation of a land bridge to Australia about 43,000 years ago as ice age sea levels declined) without using fire to modify the environment there,[6][7][8] implying that at least in this case hunting was the most important factor. It has also been suggested that the vegetational changes that occurred on the mainland were a consequence, rather than a cause, of the elimination of the megafauna.[6] This idea is supported by sediment cores from Lynch’s Crater in Queensland, which indicate that fire increased in the local ecosystem about a century after the disappearance of megafaunal browsers, leading to a subsequent transition to fire-tolerant sclerophyll vegetation

justin heywood5:39 pm 01 Jul 13

troll-sniffer said :

bundah said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

New evidence suggests that humans with their pointy spears were the main reason for megafauna extinction and climate change has bugger all to do with it given that megafaunal species comfortably survived two million years of climatic oscillations, including a number of arid glacial periods, before their sudden extinction.

Yes and those of us who keep up with a good broad smattering of research trends would point out that the bipedal invaders with pointy sticks did not actually hunt the megafauna to extinction in most cases, rather it was changes in the vegetation and other associated factors due to an introduction of a fire regime that did it in for most species occupying precarious evolutionary niches. The added pressure of hunting would have been a factor but it was not the only cause.

As an example of the advances in knowledge, it now seems likely that the end of the dodo, that most famous of extinctions, was not due solely to hunting. It seems that introduced animals such as rats and cats and the like were the final nail in the coffin.

And so it probably was for the Aussie megafauna. Chances are the environment was difficult for them. Chances are the new bipedal invaders reduced their numbers substantially through hunting. Chances are that changes in vegetation brought on by the bipedal invaders’ impact were then sufficient to finish them off.

Changes in virtually any aspect of our planet are rarely due to a single cause, which is why any scientist advocating a theory should be at pains to point out that their findings should only ever be considered as a small part of a wider picture.

While it is absolutely correct to be suspicious of any single cause theory, in this case it may well be fairly black and white.
There is a LOT of evidence pointing to a general extinction of megafauna at about the same time as the arrival of humans. These species had survived even ice ages before, but disappeared at a time when, relatively speaking, the climate was not changing rapidly.
This is certainly circumstantial evidence, but it would be a remarkable coincidence if humans were not the cause. They most certainly were the cause of mass extinctions on many other islands.

Opponents of the this theory almost always give Cuddie Springs as the best evidence that humans and the megafauna coexisted for many thousands of years. However, there are more than a few questions surrounding the archaeological integrity of the site (and this is considered their BEST evidence)

The debate is also remarkable for the heat it generates in normally staid journal articles. The opposing authors attack each other almost personally, with clear accusations of sloppy science and vague accusations of racism.

Time Team it ain’t.

As an example of the advances in knowledge, it now seems likely that the end of the dodo, that most famous of extinctions, was not due solely to hunting. It seems that introduced animals such as rats and cats and the like were the final nail in the coffin.

Apparently the dodo was pretty much inedible. In simple terms, it tasted like crap….

troll-sniffer4:50 pm 01 Jul 13

bundah said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

New evidence suggests that humans with their pointy spears were the main reason for megafauna extinction and climate change has bugger all to do with it given that megafaunal species comfortably survived two million years of climatic oscillations, including a number of arid glacial periods, before their sudden extinction.

Yes and those of us who keep up with a good broad smattering of research trends would point out that the bipedal invaders with pointy sticks did not actually hunt the megafauna to extinction in most cases, rather it was changes in the vegetation and other associated factors due to an introduction of a fire regime that did it in for most species occupying precarious evolutionary niches. The added pressure of hunting would have been a factor but it was not the only cause.

As an example of the advances in knowledge, it now seems likely that the end of the dodo, that most famous of extinctions, was not due solely to hunting. It seems that introduced animals such as rats and cats and the like were the final nail in the coffin.

And so it probably was for the Aussie megafauna. Chances are the environment was difficult for them. Chances are the new bipedal invaders reduced their numbers substantially through hunting. Chances are that changes in vegetation brought on by the bipedal invaders’ impact were then sufficient to finish them off.

Changes in virtually any aspect of our planet are rarely due to a single cause, which is why any scientist advocating a theory should be at pains to point out that their findings should only ever be considered as a small part of a wider picture.

justin heywood said :

howeph said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

Roundhead89, you must be smarter than me, because I can’t see any climate change myth crashing down.

Please explain.

In fact, a change in the climate is one of the competing theories in explaining the disappearance of the megafauna. A very interesting topic, but a bit of a perfect storm of competing scientific theories unfortunately complicated by politics.

I just wanted to check that Roundhead89 wasn’t conflating the *real* scientific debate between palaeontologists and anthropologist regarding the causes for the extinction of Australian megafauna and the *fake* debate between climatologists and climate change deniers.

thebrownstreak694:11 pm 01 Jul 13

Deref said :

DrKoresh said :

I was under the impression that our atmosphere lost the oxygen required to allow the existence of most giant animals, but I may have been completely mislead when I heard that.

I think you’re thinking of those huge insects that were around a long time before this.

Occam’s Razor – big, slow, tasty herbivours with no previous predators therefore probably no fear or predatory animals, suddenly confronted with an uberpredator with sharp, pointy sticks and a taste for delicious animals…

Unless there’s strong evidence to the contrary, I’d say we done it.

We’re talking about wooley mammoths here, right?

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

New evidence suggests that humans with their pointy spears were the main reason for megafauna extinction and climate change has bugger all to do with it given that megafaunal species comfortably survived two million years of climatic oscillations, including a number of arid glacial periods, before their sudden extinction.

Probably important to point out this is not anthropogenic climate change, note the timeframes of 50,000+ years ago.

DrKoresh said :

I was under the impression that our atmosphere lost the oxygen required to allow the existence of most giant animals, but I may have been completely mislead when I heard that.

I think you’re thinking of those huge insects that were around a long time before this.

Occam’s Razor – big, slow, tasty herbivours with no previous predators therefore probably no fear or predatory animals, suddenly confronted with an uberpredator with sharp, pointy sticks and a taste for delicious animals…

Unless there’s strong evidence to the contrary, I’d say we done it.

justin heywood3:23 pm 01 Jul 13

howeph said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

Roundhead89, you must be smarter than me, because I can’t see any climate change myth crashing down.

Please explain.

In fact, a change in the climate is one of the competing theories in explaining the disappearance of the megafauna. A very interesting topic, but a bit of a perfect storm of competing scientific theories unfortunately complicated by politics.

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

Roundhead89, you must be smarter than me, because I can’t see any climate change myth crashing down.

Please explain.

DrKoresh said :

I was under the impression that our atmosphere lost the oxygen required to allow the existence of most giant animals, but I may have been completely mislead when I heard that.

Oxygen concentration limits the size of invertebrates because they breathe via diffusions. Oxygen concentration is less restrictive when you can pump it with lungs. But as always, caveats:(http://rspb.royalsocietypublishing.org/content/early/2010/03/04/rspb.2010.0001.full)

davo101 said :

Diggety said :

Gungahlin Al said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

I’d be interested in any source you can cite that blamed megafauna extinctions on climate change?

Start here: http://theconversation.com/climate-change-wiped-out-australias-megafauna-13966

It’s been a topic of debate for quite a while.

And I bet you this bit of work is not the final word on the subject. For a start it’s based on a single sediment core and you have to infer when the various species became extinct by noting when they stop appearing in the fossil record.

Probably anther case where the press release version is far more strident than the evidence would support. If the journal paper wasn’t behind a pay-wall we might be able to see what the scientists were telling other scientists.

I don’t really have opinion on the matter actually. It’s not my area of science – I just find the discussion an interesting read.

Diggety said :

Gungahlin Al said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

I’d be interested in any source you can cite that blamed megafauna extinctions on climate change?

Start here: http://theconversation.com/climate-change-wiped-out-australias-megafauna-13966

It’s been a topic of debate for quite a while.

And I bet you this bit of work is not the final word on the subject. For a start it’s based on a single sediment core and you have to infer when the various species became extinct by noting when they stop appearing in the fossil record.

Probably anther case where the press release version is far more strident than the evidence would support. If the journal paper wasn’t behind a pay-wall we might be able to see what the scientists were telling other scientists.

Gungahlin Al said :

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

I’d be interested in any source you can cite that blamed megafauna extinctions on climate change?

Start here: http://theconversation.com/climate-change-wiped-out-australias-megafauna-13966

It’s been a topic of debate for quite a while.

Gungahlin Al12:59 pm 01 Jul 13

Roundhead89 said :

Oh dear. Crash goes another climate change myth.

I’d be interested in any source you can cite that blamed megafauna extinctions on climate change?

johnboy said :

Don’t tell the elephants

That’s why I qualified my statement with the word “most”, smarty-pants :p

I was under the impression that our atmosphere lost the oxygen required to allow the existence of most giant animals, but I may have been completely mislead when I heard that.

Don’t tell the elephants

Gungahlin Al said :

Human beings hunt easily-hunted fauna to extinction. Nothing’s new in the world…
Endangered 140-year-old Orange Roughy with your chips anyone? Get it from the fish shop in the Canberra Centre.

Excellent book the Future Eaters.

Reptoids, they just ate the f*ck*n lot of them….

Oh dear. Crash goes another climate change myth.

Gungahlin Al10:45 am 01 Jul 13

Human beings hunt easily-hunted fauna to extinction. Nothing’s new in the world…
Endangered 140-year-old Orange Roughy with your chips anyone? Get it from the fish shop in the Canberra Centre.

I’m pretty sure I had already read that in The Future Eaters?

Megafauna tasted good.

Pointy sticks and sharply,ah penetrating puns indeed, although the massive fires may have been triggered by multiple lightning strikes..

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