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.
Peaceful indigenous peoples, living in harmony with their environment, while they exterminate the megafauna.
Maybe that could be rephrased.
So, how many megafauna species went extint in Africa upon initial expansion of humankind?
His conclusions are built on weak sand. Just because he can’t find another explanation and, automatically saying “Humans are responsible” is unsupported. Why then are elephants still around after tens of thousands of years of co-existence with humans? Stop and think about the task of killing an elephant sized creature with a spear. I saw a TV show a few years ago and the stone age tools tested against mock elephants barely punctured the skin, let alone inflicted a mortal wound. Experimental test showed the “Exterminator” hypothesis to be highly unlikely.
It seems more likely that the researcher found an explanation that he was very politically satisfied with, and chose to stop looking.
Another fantasy paper.
First eliminate all the theories you don’t like, then whatever is left, no matter how unlikely, must be the truth.
I blame the Koch brothers. Were they around then? Has anyone checked?
Why then are elephants still around after tens of thousands of years of co-existence with humans?
Because elephants can be domesticated.
Stop and think about the task of killing an elephant sized creature with a spear.
It’s pretty easy if you put the spear in a pit and then get the elephant to fall on it.
Well, they were big, tasty, and some of them wanted to eat us. What else could we do?
On my first wander through a pristine forest in the North Island of New Zealand, I was struck by the lack of noises, no scuttling in the under brush and bird calls when compared to my native Australia.
Finally it dawned on me, the Maori’s had eaten everything (except each other).
Thankfully for them, the sheep and breweries arrived in the nick of time, courtesy of the much maligned Pakeha ha ha ha ha.
The point about the species surviving all but the last ice age, when mankind appears in force,
is particularly telling. The whole problem (at least for the prey animals) is that the human populations were expanding much faster than the animal populations. It is aso true that a prey animal species can be exterminated by animals that prey on them other than man. That’s life in this dog-eat-dog world of ours. Think I’ll go eat some chicken.
The reason why elephants survived, and many African species compared to other places, is that the elephant and other African species evolved alongside humans. They knew to avoid humans. Which is why African elephants are so aggressive towards humans. Big game in North America, however, had no such instinct.
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?
This study:
Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans.
by Professor Stanley H. Ambrose,
Department of Anthropology, University Of Illinois, Urbana, USA
Extract from “Journal of Human Evolution” [1998] 34, 623-651
suggests that: “Human population size fell to about 10,000 adults between 50 and 100 thousand years ago.” This was supposedly due to a volcanic eruption that resulted in a six year long volcanic winter. By 10,000 years ago, the human population is estimated to have been about 5,000,000.
So,
1) If the volcanic winter was this hard on humans, why would it not be hard on other large mammals
2) Is it physically possible for a human population between 10,000 and 5,000,000 to over-hunt or out-compete so many species that outnumbered them (American bison alone are estimated to have numbered 60,000,000 before 1492, while being hunted by humans who used such tactics as chasing herds over cliffs).
In defense of my species, look at this way : humans did not : 1) know they were driving these prey animals to extinctions , nor 2) did humans WANT to drive them to extinction, which would mean no more elephant burgers.
While I agree that climate change is unlikely to have caused these extinctions, I find it difficult to believe that early man could have hunted them to extinction. Predators almost never hunt their prey to extinction, without modern weaponry, I don’t see how early North American man could have had any greator impact on say the Columbia Mammoth than precolonial Africans would have on the African Elephant.
I think the clue to what might have really happened lies in the geographical distribution of megafaunal species loss. The Americas seem to have taken the biggest hit, Africa the lowest hit. Perhaps there was an event such as a meteor strike which we don’t fully understand?
Lack of evidence for one theory is not proof of another theory. Theirs is an argument from ignorance on a false dichotomy.
It’s abundantly clear that humans hunted those animals to extinction, and has been abundantly clear all along to any sensible thinker–I’ve had no doubts about this since I was a boy, despite all the appalling museum displays I’ve seen which blamed climate. Of course it was pre-McDonalds people in pursuit of early burgers. Here in NZ we had the moas, promptly hunted to extinction by the first settlers (the Maoris) 1000 years ago — we even have the old middens here with the bones of 1000s of moas cooked en masse, yum yum. Anyone who thinks otherwise simply doesn’t understand “life, the universe, and everything”.
The key point in the argument put forward (as explained in detail in books like Jared Diamond’s “Guns, Germs, and Steel”) is that these mass megafauna extinctions occurred in places — the Americas, Australia — where modern humans effectively burst upon the scene a few tens of thousands of years ago.
They did not occur where humans had gradually evolved over hundreds of thousands, or even millions of years — notably, Africa — in the presence of these species. The idea is in this case, the species had the chance to adapt evolutionarily to the gradual improvement in human hunting skills. In other cases, they did not get that chance.
Correct? Who knows? But it is the most plausible explanation I’ve heard.
Steve R says:
June 4, 2014 at 12:54 pm
No need to posit extraterrestrial intervention. Prey species were wary of & accustomed to people in Africa, less so in Europe & Asia, but not at all on Australia & in the Americas.
Columbian mammoth sites have been found with Clovis points inside the beasts in such a way as to suggest killing rather than scavenging. Archaic Indians stampeded big horned bison over cliffs.
Humans could have wiped out the megafauna of North America as they did previously in Australia & subsequently on New Zealand & other isolated oceanic islands.
The reason we didn’t wreak as much havoc in Africa is that the indigenous megafauna there grew up with human predation over millions of years, if you go back to H. habilis, the first stone tool maker. On Australia & in the Americas, prey animals were naive & easily slaughtered. Europe & Asia are intermediate cases.
IMO climate change did play a role, in that the species going extinct at the Holocene transition were under stress already. They might have survived that glacial/interglacial transition, as some of them had previous ones, but for the added pressure on their numbers from human hunting.
Hi Arthur;
your comment “humans did not : 1) know they were driving these prey animals to extinction…”
Sorry, but for sure the Maori’s knew it would happen eventually, since being the runts of the village they were kicked out of (in best guestimate historical order) Tonga, Tahiti and Hawaii. After NZ – next stop Antarctica
Oh no, my bad of course they were not merely hungry, rather they were intrepid explorers – yeah right (sarc)
talldave2 says:
Stop and think about the task of killing an elephant sized creature with a spear.
It’s pretty easy if you put the spear in a pit and then get the elephant to fall on it.
Everything is easy for those who don’t have to do it themselves.
I personally think that making a spear stong enough to survive elephant falling on it and not break and mount it in the ground so it doesn’t move and digging the pit without shovels and, most importantly, getting the elephant to fall on it is not that easy.
I’d like to see some estimates as to how many spears need to be made and how many pits need to be dug and how long it would take, etc. given the estimate of human population and population of megafauna we supposedly killed off. Somehow it just doesn’t feel right. After all, only after invention of fire arms we started to make a dent in population of such things as buffalo, elephants, tigers, bears, wales and others.
I think my 7 year old daughter had the best explanation for the fact that animals were never so large after the demise of the dinosaurs: ‘Oh,’ she said, ‘I expact God thought “Nah, too big — let’s rub them out and start again.”‘ Which is as good a reason as any other.
Wrong Udar,
“After all, only after invention of fire arms”
see the previous posts on NZ, the Maori’s were beginning to get hungry long before the (tasty) Pakeha arrived. All achieved with wooden spears and stone clubs
“no intentional PC here” CNXTim
”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. ”
No they were residents of Eurasia as long ago as 300,000 to 600,000 yrs ago! Ya know, folks, being an expert on the big animals is only half the required knowledge. I hope you aren’t ”finding” correlation as your causation here (100,000 yrs), not because of the usual caveat but because it doesn’t correlate even. I was admonished by Pamela Gray on the ‘sunspot’ thread earlier today for suggesting authors of the paper had far exceeded fair possibilities outside of the science. In this case I agree wholeheartedly with Pamela’s admonition.
http://wattsupwiththat.com/2014/06/03/solving-sunspot-mysteries/
”Gary Pearse says:
June 4, 2014 at 7:57 am
Pamela Gray says:
June 4, 2014 at 7:08 am
”Gary, it IS the station of scientists to be exceedingly curious about what they don’t know.”
Your simplistic statement is correct, but that is not the topic of my blurb (re-read the whole). If you think it is the topic, then Pamela, what is the limit? Should a solar scientist be extrapolating as to why egg yokes, sugar, salt, mustard and vinegar can be whipped into mayonnaise?”
I see that my right wing, Republican, neocon, nonveggie, caveman ancestors were a lot busier hunting than I thought.