Results show that the correlation between climate change … and the loss of megafauna is weak
A new study unequivocally points to humans as the cause of the mass extinction of large animals all over the world during the course of the last 100,000 years.
Was it mankind or climate change that caused the extinction of a considerable number of large mammals about the time of the last Ice Age? Researchers at Aarhus University have carried out the first global analysis of the extinction of the large animals, and the conclusion is clear – humans are to blame.
“Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals,” says Postdoctoral Fellow Søren Faurby, Aarhus University.
Was it due to climate change?
For almost 50 years, scientists have been discussing what led to the mass extinction of large animals (also known as megafauna) during and immediately after the last Ice Age.
One of two leading theories states that the large animals became extinct as a result of climate change. There were significant climate changes, especially towards the end of the last Ice Age – just as there had been during previous Ice Ages – and this meant that many species no longer had the potential to find suitable habitats and they died out as a result. However, because the last Ice Age was just one in a long series of Ice Ages, it is puzzling that a corresponding extinction of large animals did not take place during the earlier ones.
Theory of overkill
The other theory concerning the extinction of the animals is ‘overkill’. Modern man spread from Africa to all parts of the world during the course of a little more than the last 100,000 years. In simple terms, the overkill hypothesis states that modern man exterminated many of the large animal species on arrival in the new continents. This was either because their populations could not withstand human hunting, or for indirect reasons such as the loss of their prey, which were also hunted by humans.
First global mapping
In their study, the researchers produced the first global analysis and relatively fine-grained mapping of all the large mammals (with a body weight of at least 10 kg) that existed during the period 132,000–1,000 years ago – the period during which the extinction in question took place. They were thus able to study the geographical variation in the percentage of large species that became extinct on a much finer scale than previously achieved.
The researchers found that a total of 177 species of large mammals disappeared during this period – a massive loss. Africa ‘only’ lost 18 species and Europe 19, while Asia lost 38 species, Australia and the surrounding area 26, North America 43 and South America a total of 62 species of large mammals.
The extinction of the large animals took place in virtually all climate zones and affected cold-adapted species such as woolly mammoths, temperate species such as forest elephants and giant deer, and tropical species such as giant cape buffalo and some giant sloths. It was observed on virtually every continent, although a particularly large number of animals became extinct in North and South America, where species including sabre-toothed cats, mastodons, giant sloths and giant armadillos disappeared, and in Australia, which lost animals such as giant kangaroos, giant wombats and marsupial lions. There were also fairly large losses in Europe and Asia, including a number of elephants, rhinoceroses and giant deer.
Weak climate effect
The results show that the correlation between climate change – i.e. the variation in temperature and precipitation between glacials and interglacials – and the loss of megafauna is weak, and can only be seen in one sub-region, namely Eurasia (Europe and Asia). “The significant loss of megafauna all over the world can therefore not be explained by climate change, even though it has definitely played a role as a driving force in changing the distribution of some species of animals. Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer,” says Postdoctoral Fellow Christopher Sandom, Aarhus University.
Extinction linked to humans
On the other hand, the results show a very strong correlation between the extinction and the history of human expansion. “We consistently find very large rates of extinction in areas where there had been no contact between wildlife and primitive human races, and which were suddenly confronted by fully developed modern humans (Homo sapiens). In general, at least 30% of the large species of animals disappeared from all such areas,” says Professor Jens-Christian Svenning, Aarhus University.
The researchers’ geographical analysis thereby points very strongly at humans as the cause of the loss of most of the large animals.
The results also draw a straight line from the prehistoric extinction of large animals via the historical regional or global extermination due to hunting (American bison, European bison, quagga, Eurasian wild horse or tarpan, and many others) to the current critical situation for a considerable number of large animals as a result of poaching and hunting (e.g. the rhino poaching epidemic).
The results have just been published in the article Global late Quaternary megafauna extinctions linked to humans, not climate change in Proceedings of the Royal Society B.
Geology Joe says:
June 4, 2014 at 12:45 pm
Geology Joe says: Stop and think about the task of killing an elephant sized creature with a spear.
TallDave2 Says:
It’s pretty easy if you put the spear in a pit and then get the elephant to fall on it.
Geology Joe says: Or you could just play it sad music until it’s overcome with melancholy and it swallows it’s own trunk. Much more humane and about as likely. Have you ever hunted anything?
Wow Mr. Geology Joe. There is a lack of knowledge exhibited in your post. There are archeological sites showing man with stone age tools successfully hunted elephants. Take some time to read a bit.
This latest study is not the last word on the debate of what killed the large species, but it and many others does make it look like man had a big part in it. The stone age man wasn’t some ecologist who carefully considered his impact on the surrounding nature. That meme is a joke kinda like your question: “Have you ever hunted anything?”
We were taught this in college 30 years ago. The AGW cabal has corrupted every branch of science that we need to go back and re-learn actual settled science.
Nah, it is all the fault of the extra CO2 exhaled by all the extra humans.
talldave2 – did you ever try to domesticate an African Elephant?
How about a megafauna kill-off modeling program funded by the National Science Foundation? Or maybe a simulation program funded by the Department of Energy if some kind of causal relationship could be theorized between prehistoric rates of energy consumption and the number of fires being lit for cooking up all those woolly mammoths?
For those who think it was hard for early peoples to hunt these large animals, compare it to how hard it is to start a fire using only stone & wood. You try that. But the early peoples indisputably did start those fires, so let’s have no more reservations about their capability. They started those fires and hunted those animals and had some great feasts in those days. The Amerindians had a cultural memory of those days, they called it “the happy hunting grounds”.
My gut feeling is that the answer is too easy, and in the current scientific client, a very fund friendly, human are bad, theory. I have no problem thinking that humans on an Island, even really big ones, might exterminate animal populations. Less so on continents where there were likely sizable populations that never came into contact with the sparse native tribes. If they had gone extinct less than a thousand years ago, I might buy it, but ten-thousand. Can’t see it. Why were the bison so numerous if Man was so deadly to the mega-fauna?
Makes me ask the question, what if the Bison out competed some of the other large grazing animals? Smaller less protective herds of other mega-fauna were easier prey to large predators.
For instances the Giant Sloth did not travel in herds as far as I know.
Large predators were not numerous, and would have a habit of dining on humans, making their extermination a must for reasons other than food.
Not saying the theory is not true. Hardly an expert. Just with all the ‘human are bad’ memes floating around these days I take any study that blames us for something with a grain of salt.
Wait a minute! Hold the phone! I have been told by many a vegetarian that man simply did not evolve to eat meat. So, apparently Homo sapiens caused all of these extinctions by out-grazing the mega-fauna.
Sorry, had to throw that in.
About 3 million years ago, Panama arose out the sea and connected previously separated North & South America. This allowed the Saber tooth tiger to enter South America where they immediately reeked havoc and drove pretty much all of South America’s Ungulates, marsupials and large predators like Terror Birds extinct.
Now if small numbers of saber tooth tigers acting individually can drive a large number of animals extinct then it’s not much of a stretch to see groups of humans who compared to Sabertooths are much more efficient and diverse hunters doing the same.
Especially considering one of early man’s hunting strategies was to cause stampedes and drive whole herds of animals right off the sides of cliffs.
To eat an elephant, first, dig your hefalump pit, then,
encourage your elephant to fall into the hefalump pit,
(impaling said elephant on spear inside pit is considered optional)
then, invent your choice of:
jack, hoist, lift, winch, crane, block-and-tackle, hefalump chair, soap-on-a-roap
and get your 5 tons of yumyum out of the pit again.
parboil with a pinch of lemon-n-lime and feast away.
When a broken limb, or ever even a bad cut, means you will likely die, you don’t take unnecessary risks. I simply can’t see ancient man targeting mega-fauna if there was any easier prey available. And if they did do it, they would not do it in a head-on encounter.
They would be opportunistic, however. If they came across an injured mega-fauna which they could stick spears in safely. it would be well worth their time to take a few days killing it, seeing as most of that time would be keeping off other predators while they waited for it to die.
Wonder if we are missing an important factor. Dogs, or at that time, mostly wolves. A human tribe associated with what was in effect a really large wolf pack would need a great deal of meat, and the canines would give them the ability to hunt prey that they would not otherwise attempt.
What is an atlatl?
http://en.wikipedia.org/wiki/Spear-thrower
Does this imply that the incisors most of us have in our mouths have to be a recent edition to our food chewing tool kit? Possibly driven by the emergence of the Mammoth Burger as a popular human dietary staple — the Big Mac and the Whopper of their era?
milodonharlani says:
That is only part of it. Another factor is that the expansion from Africa was over many thousands of years. As humans got farther away from Africa, they increased not only their hunting skills, but their weaponry. At first they only had crude clubs, knives and spears as weapons.
Then some genius of his time found if you use a short stick with a notch at one end you have a long range weapon that can throw a spear a over 150 km/h. He invented the atlatl. and invented the atlatl which dates from from about 400,000 years ago.
http://en.wikipedia.org/wiki/Atlatl#History
Later humans developed the bow and arrow, in use for abut 30,000 years, with even more range and killing power.
Has anybody got a count on the number of spear points found with megafauna skeletons? Do you have any idea what percentage of kills are found by archaeologists? And people are still arguing that humans couldn’t kill off individuals, let alone species! How naive can it get? –AGF
I don’t buy it….there weren’t enough ‘humans’ around
Could have been something as simple as a virus…..carried by humans
This is an old argument. It holds little water. The animals during the last glaciation were far more specialized then the last time about, e.i, the animals at the end of the previous glaciation were different. The last two glacial-to-interglacial transitions are not particularly comparable either from a biological point of view.
Full sized elephants were likely very safe from humans and their weapons. Baby elephants not so much. Get them in the first hours after birth and you have an easy meal for dozens.
Damn 🙂 “elephants” s/b “mega fauna”. I’m suffering pachyderm fixation.
For those that don’t think humans can easily cull animals to extinction, consider that humans took the American Bison herds from 30-60 million down to less than 1000 in a mere two hundred years or less.
I still have concerns, among other things such as competition for available food supplies, catastrophic events (major volcanic eruptions, meteorite impacts, etc.), I suggest the following:
1) This is noted as a “first-of-a-kind” analysis, thus it has relatively abundant potential to be … well, … wrong (look at all the flip-flopping scientific studies purporting that chocolate, wine, beer, red meat, etc., are bad for humans’ diets);
2) The study focuses on the period only since the last Ice Age;
3) There appears to be no data for extinctions following any of the prior Ice Ages against which to compare (what might be expected “naturally” during an interglacial period;
4) The authors make a broad implicit assumption that natural causes were not adequate, so therefore it must be humankind and the expansion of human populations;
5) The potential for food chain impacts does not appear to be fully explored and coupled with the relatively small size of the large vs. small mammal distinction (10 kg or 22 lbs) strikes me as being a very broad range;
6) What number and/or percentage of “large mammal” species remains from that period; the implication is very, very few if any;
7) Likewise, it is not apparent if any number of “large mammal” species have come into existence since 132,000 years ago;
8) I have seen “documentaries” on television that suggest some large animal species (not just mammals) may have had a predilection toward extinction as the Earth warmed after the last Ice Age (i.e., natural causes); and
9) It’s not clear if evolving disease (bacterial, virus, fungal or other vectors) have received adequate consideration.
This is complicated stuff, lots of variable and competing theories. Clearly, the westward push of European settlers would not have caused the natural demise of many animals, mammals or not… For example, take Big Bone Lick State Park, KY:
Source: http://parks.ky.gov/parks/historicsites/big-bone-lick/history.aspx
Clearly humans did not create the bog-like soils…
In the end, it’s probably a bit of all causes, and we just haven’t the data to differential the impacts of each particular cause. We here at WUWT and other like-minded individuals — those interested in proper scientific investigation — will have to wait for concurring research.
Other teamwork involved using fire to rout and drive whole herds off cliffs. The atlatl probably helped, Wiki noted a modern range of 260 meters, I had previously read they are accurate to 100 yards, which seems in line.
To quote a former colleague (albeit in another, technical, context):
Adapt, or die.
Greens want macroevolution, well, here’s their chance…
Oh, wait….these creatures didn’t adapt….
A cynic would say that’s because they didn’t have the IPCC to warn them (probably off flagging trains down somewhere)….
Why is it that “man” is always at fault, when it’s folks like “Mann” who are obfuscating the real issues?
Why would spear-carrying clovis hunters target the short faced bear, twice as large as a grizzly, and the lions and tigers when much easier prey was available. It would be dangerous and foolhardy not to mention resource sapping to hunt these predators. This theory is utter nonsense.
I cannot comment on the global megafauna die off but a large number of the large animals and a number of spices of horses did go completely extinct in North America just about the height of the last glacial period in NA (Wisconsin). Most archaeologists have continued to propose that Clovis man was the earliest human in NA (or SA for that matter). Evidence for Clovis man as early as the beginning of the present interglacial is extensive in NA. I think there is some limited evidence of pre-Clovis man in NA but it is so limited and scattered that population levels of these people cannot be considered a threat to the NA fauna. Archaeology like Climate Science has a large vocal majority while at the same time there are a few folks who do not have their minds made up yet. The few do think positively about and have some evidence of pre-Clovis man but they would probably agree that climate was more likely to be the cause (if you discounted a large cometary event about that time – which personally I don’t completely discount yet). You can’t have it both ways. If there were no or few humans here until around the beginning of the present interglacial then they could not be the reason for a animal die off in North America.
Bernie
Sorry spell checked after sending species of horses