Hunters, not climate change, killed giant beasts 40,000 years ago

Mar 22, 2012 by Justin Norrie
The Diprotodon optatum, a marsupial mega-herbivore sometimes known as the Giant Wombat or the Rhinoceros Wombat, grew to three metres in length and two metres in height. Its closest surviving relatives are the wombat and the koala. Peter Murray

The first Australians hunted giant kangaroos, rhinoceros-sized marsupials, huge goannas and other megafauna to extinction shortly after arriving in the country more than 40,000 years ago, new research claims.

A team of scientists from six universities say they have put an end to the long-running debate about the cause of the sudden disappearance of giant from the Australian ecosystem, and the dramatic change to the landscape that followed.

Soon after the beasts disappeared, there was a rapid shift in vegetation across Australia. Once covered by patches of rainforest separated by areas of open grassland, it was soon smothered by eucalypt forest, the researchers say.

The change was caused by a decrease in consumption of by large , which allowed forest to spread and also resulted in a build-up of dry fuel for .

In the past 100,000 years, many of the largest animals on Earth became extinct. The reasons remain contentious. In recent years, some scientists have argued that through or fire was the killer blow.

But the latest argument, published today in Science, refutes this.

Research leader Chris Johnson, from the University of Tasmania School of Zoology, said the team solved the mystery of the disappearance of Australia’s megafauna by using a method of tracking large herbivores through time by counting the spores of fungi in their dung.

Professor Johnson said the biggest herbivores – “rhino-sized wombat-like marsupials called Diprotodons, giant kangaroos, a goanna bigger than the living Komodo dragon, a giant goose twice the size of the emu and many others” – produced vast quantities of dung, and that there were special fungi that lived in it.

“The spores of these fungi can be preserved in sediments in swamps and lakes,“ Professor Johnson said. "As those sediments accumulate over time, they create a historical record of the abundance of very large herbivores in the environment.

“Pollen and charcoal particles are trapped in the same sediments, so that it is possible to match up the history of abundance of large herbivores with changes in vegetation and fire. Then, radiocarbon can be used to date these things.”

Sthenurus, the giant kangaroo, grew up to three metres in length, or about twice as big as its modern-day ancestor. Peter Murray

Professor Johnson said the research focussed largely on a swamp called Lynch’s Crater in northeast Queensland, where the sediment record reaches back to 130,000 years ago.

“It showed that the abundance of large mammals was stable until just before 40,000 years ago, when it suddenly crashed.

“This rules out climate change as a cause of extinction, as there were several periods of climate drying before the extinction and they had no effect on abundance. And when the animals did go extinct, the climate was stable.

Habitat change could not have been responsible for the loss of the large marsupsials, because the grassy forest expanded only after the spores abruptly declined.

“But the extinctions followed very soon after the time that people arrived in the region – so it seems that people did it,” Professor Johnson said.

“Our study didn’t directly address how people caused extinction, but the most likely mechanism is hunting. Quite a bit of other circumstantial evidence suggests that.”

The results also show that the extinctions were quickly followed by massive ecological change.

Gavin Prideaux, a lecturer in vertebrate palaeontology in the School of Biological Sciences at Flinders University, said the research was an important contribution to the understanding of what happened “when 90% of our large terrestrial species disappeared, depriving us of the sight of giant short-faced kangaroos, marsupial "lions”, giant horned tortoises and herds of Diprotodons meandering through the outback."

The research team had presented compelling data in a field of inquiry that “aches under the strain of opinion pieces and the tired reworking of published data … The timing of the inferred extinction coincides with early human presence in the region, but not with significant climatic change.”

This supported a mounting number of studies that have argued that climate change was not primarily responsible for extinctions in other parts of the continent, Dr Prideaux said.

John Alroy, a Future Fellow in the Department of Biological Sciences, Faculty of Science at Macquarie University, said the new research put all debate over the matter to rest. “The key new data are the spore counts, and in combination with the charcoal and rainforest pollen data they tell the whole story,” Dr Alroy said. “There is simply no reasonable way to argue with the authors' conclusions.”

But Judith Field, a Senior Research Fellow in the School of Biological, Earth and Environmental Sciences at The University of New South Wales, said the argument was flawed for several reasons.

Chief among these was the claim by the authors that climate was stable through the period in question – “the opposite is generally accepted”, Dr Field said – and the unproven assumption that megafauna were so abundant that their disappearance would have triggered a drastic change in vegetation.

“The facts of the matter are that most megafauna were extinct nearly 100,000 years before human arrival and there is no evidence for any particular time period to be significant in terms of faunal extinctions.”

Dr Field added that there was no evidence from archaeological sites that humans hunted . She said the earliest evidence for human occupation in northeast Queensland suggested their populations were small.

Explore further: Stranded pilot whale rescued in Cape Verde

More information: www.sciencemag.org/content/335/6075/1483.abstract

Source: The Conversation

4.8 /5 (12 votes)

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User comments : 25

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NotParker
1.6 / 5 (28) Mar 22, 2012
Duh!

And hunters kill 1,000 polar bears a year ... not climate change.
Astricus
5 / 5 (2) Mar 22, 2012
The Extinct Neanderthals ( not extinct at all! ) hunted the European Bison almost to extinction.
StarGazer2011
1.7 / 5 (22) Mar 22, 2012
this is more about narrative construction. The idea that 'dangerous climate change' killed off the megafauna fits nicely, the idea that indigenous Australians killed them off is anathema to several control narratives.
I wouldnt expect this research to get much traction, its politically incorrect.
sherriffwoody
5 / 5 (3) Mar 22, 2012
But film and govt around the world have us believe that people native to a region are at one with nature. how could this be?
Pediopal
1 / 5 (12) Mar 22, 2012
The new date for the colonization of Australia was closer to 50,000 years ago. If this newest date is correct then it took 10,000 years for humans to kill off the mega fauna. This makes the mega fauna extinction by man in Australia a rather controversial one.
Estevan57
2 / 5 (29) Mar 22, 2012
"John Alroy, a Future Fellow in the Department of Biological Sciences, Faculty of Science at Macquarie University, said the new research put all debate over the matter to rest."

"But Judith Field, a Senior Research Fellow in the School of Biological, Earth and Environmental Sciences at The University of New South Wales, said the argument was flawed for several reasons."

Obviously this theory needs some work.

A dingo ate my megafauna! A dingo ate my megafauna!
Sorry, couldn't resist.
Pediopal
1.5 / 5 (14) Mar 22, 2012
Along the same lines in the Americas where recent dates of the Paleo-Indians arrival are close to 14,000 years ago and the extinction of mega fauna between 12 and 8 thousand years ago pretty well put the extinction by humans to bed here too. Not saying they didnt dine on mega fauna once in awhile but really folks just think about the logistics of hunting to extinction all of these animals with only your own two feet and a few spears to do it with. Lot different than running them down with snowmobiles and 4-wheelers or shooting from aircraft and using high powered rifles. Do not believe me? Then this weekend grab your favorite butcher knife strip to your skivvies and head for the woods lets see what you bring home for the pot.
Sinister1811
1.4 / 5 (19) Mar 22, 2012
when 90% of our large terrestrial species disappeared, depriving us of the sight of giant short-faced kangaroos, marsupial "lions, giant horned tortoises and herds of Diprotodons meandering through the outback."


Apparently, the climate was much different when these animals were around. So, maybe the indigenous people and climate change were both to blame. Or maybe many of these large animals were dangerous, such as the Marsupial Lion, Megalania and the "Demon Duck of Doom", so the indigenous people hunted them to extinction. Certainly an interesting thought.
Sinister1811
2 / 5 (20) Mar 22, 2012
But yeah, I wish we could go back in time and see these things.
_etabeta_
1.5 / 5 (8) Mar 23, 2012
40,000 years ago Australia was not a country.
Pkunk_
2.1 / 5 (11) Mar 23, 2012
Lot different than running them down with snowmobiles and 4-wheelers or shooting from aircraft and using high powered rifles. Do not believe me? Then this weekend grab your favorite butcher knife strip to your skivvies and head for the woods lets see what you bring home for the pot.


40,000 years back agriculture was not invented and the only way to fill your stomach was to hunt and kill your prey or die.
The fact that 40,000 years back homo sapiens was able to reach from Africa to Australia shows the intelligence of the species. You give too little credit to sapien hunters who with just a few rocks and stone spears were able to make easy prey of even large animals.
It all comes down to tactics , and a little bit of FIRE.
Wolf358
5 / 5 (1) Mar 23, 2012
"Sthenurus, the giant kangaroo, grew up to three metres in length, or about twice as big as its modern-day ancestor.
Should say "...modern-day descendant."

Just my $.02, but I suspect evidence will arise showing that the actual killer of megafauna was _disease_, which itself was spread by early humans on the move, and not the humans hunting activities by itself.

Pediopal
1 / 5 (9) Mar 23, 2012
Yes fire is one way of catching and cooking in one fell swoop for sure. Depending on the climate conditions upon arrival of man fire may or may not be a cause of extinctions. In the New World fire was used but we do not know if paleo-Indians used fire or whether early post Pleistocene climates and habitats would have accommodated huge wildfires.
Pediopal
1.4 / 5 (10) Mar 23, 2012
The questions are if fire was the exterminator of mega fauna why did some slower species that definitely could not out run fire survive. We know that more recent man used fire and we are still experiencing wildfires today that are most likely more extreme than in past times yet no species that I know of have been exterminated by fire. Mega fauna in Europe declined and became extinct during the same period as New World species did fire kills them also?
NotParker
2.1 / 5 (18) Mar 23, 2012
"A buffalo jump is a cliff formation which North American Indians historically used in mass killings of plains bison. Hunters herded the bison and drove them over the cliff, breaking their legs and rendering them immobile. Tribe members waiting below closed in with spears and bows to finish the kills. The Blackfeet Indians called the buffalo jumps "pishkun", which loosely translates as "deep blood kettle". This type of hunting was a communal event which occurred as early as 12,000 years ago and lasted until at least 1500 AD, around the time of the introduction of horses."
ffkling
5 / 5 (1) Mar 23, 2012
Considering that mankind is presently responsible for the extinction of some 30,000 animal and plant species annually, is it any surprise ancient mankind was just as foolishly destructive?
Pediopal
1 / 5 (9) Mar 23, 2012
NotParker, you are correct although the bison did not nearly reach extinction until horses, rifles and train appeared. (There is some controversy on whether the older extinct forms of bison such as Bison antiquuis and others were separate species of bison or just climatic variants of our Bison bison.) Antelope (Pronghorn) drives were spaced many years apart as the Natives knew that the species was slow to recover and doing so on a regular basis was not a very wise idea for not only the survival of the antelope but for the hunters themselves.
Sinister1811
2 / 5 (21) Mar 23, 2012
40,000 years ago Australia was not a country.


40,000 years ago, neither was the United States. What does that have to do with anything?
Sinister1811
1.7 / 5 (18) Mar 23, 2012
Considering that mankind is presently responsible for the extinction of some 30,000 animal and plant species annually, is it any surprise ancient mankind was just as foolishly destructive?


Exactly. Humans ARE the problem. This is why we don't get to see such awesome animals roaming the outback today. It's actually quite sad. And many more animals are going extinct by the minute.. :( For example; the black Rhino in Africa is now extinct due to poaching. It's pathetic.
Skepticus
1.4 / 5 (9) Mar 24, 2012
..the black Rhino in Africa is now extinct due to poaching..

On a random thought..the Chinese association of rhino horns and fecundity must have something to do with them and their relative's extinction...apparently, scientists' assertions of the worthlessness of rhino horns as aphrodisiac is an unwind piss against the Chinese's thousands of years long experimentations and utterly ignored by them..(breed, man, breed! lets outbreed the rhino unto their extinction!)
ryggesogn2
1.6 / 5 (13) Mar 24, 2012
Considering that mankind is presently responsible for the extinction of some 30,000 animal and plant species annually, is it any surprise ancient mankind was just as foolishly destructive?

If you hate your species so much, why are you still around?
Mahal_Kita
1.5 / 5 (8) Mar 24, 2012
Considering that mankind is presently responsible for the extinction of some 30,000 animal and plant species annually, is it any surprise ancient mankind was just as foolishly destructive?


Exactly. Humans ARE the problem.


Hm.. Humans just ARE. It's quite understandable why humans - a formerly unknown predator in the region - hunted giant species to extinction. And I quote: "Evidence suggests that meat constituted a substantial proportion of the diet of the earliest humans. Early hunter-gatherers depended on the organized hunting of large animals." Or.. You have to invent something like livestock. Oh.. We did that, hm? :-)
Mahal_Kita
1.6 / 5 (8) Mar 24, 2012
But yeah, I wish we could go back in time and see these things.


We would experience 'needlessly' cruel and sickeningly bloody (mass) slaughter. We have gone a long way my friend.. Or did we?

Anyway.. You wouldn't survive a day :-)
Fionn
1.6 / 5 (7) Mar 24, 2012
@ Wolf358: That's something we do need to take into account. Humans, and the plants and animals who travel with them, be they livestock, pets, stowaways, parasites, food stores or skins/trophies, carry lots of organisms of their own. The introduction of novel bacteria, viruses, paramecia, multicellular parasites and insect pests could have had as large an effect on the native population, if not larger, than human hunting and land use. We see this today in Australia with the cane toad, rabbits, foxes, mice, and camels.

I'd be interested to see this study conducted in many more regions of Australia to see if the results are uniform, and to combine it with studies of preserved micro-organisms and megafauna fossils exhibiting signs of buthcery or cooking, to see if new diseases/invasive species (other than humans) played a role, and to assess the level of active hunting, for food or predator extermination, occurred after the arrival of humans.
scidog
not rated yet Mar 25, 2012
Fionn seems to have the right idea and one that i have not see much if anything about.in Australia as well as North America people were not the only living things to arrive.a animal "smallpox" brought in from Asia or in the case of NA over the Bearing land bridge could have infected and wiped out the existing magafauna.
anyone have links to research on that?

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