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.
Interesting thread. I note that some posters have difficulty believing that man was mostly, or wholly, responsible for the extinction of mammalian (and avian) megafauna. I have no problem believing thus. As has been pointed out by others, humans when they arrived in Australia began changing the vegetation cover to suit their hunting needs, by burning. The vegetation changes did not suit the megafauna, on top of which they were hunted directly (or indirectly, in the case of carnivorous megafauna, it was their prey which was hunted by humans). As for those who seem to doubt the ability of “primitive” humans to hunt large prey, the archaeological record proves otherwise. Wooly mammoth bone was used for many purposes bu Europeans- including as fuel for their fires. The mammoths didn’t conveniently drop dead in large numbers so humans could utilise them. Even the much-maligned Tim Flannery in “The Future Eaters” leaned towards humans as the major factor in megafaunal extinctions, and there is no more obvious a culprit than humans in New Zealand. I have no doubt that climate may have been a factor in the extinction of some species in some places, but the major cause was humans. Resorting to diseases, which strangely attacked only large animals, doesn’t cut it for me.
I am not impressed with this paragraph:
“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.”
It is referring to periods of glaciation within this present Ice Age, as being “ice ages.” If such terminology is being used, and it is being used quite inaccurately, this alone indicates that the authors may not know what they are writing about.
Early man and even our own Plains Indians became adept at driving herds of animals to their death over cliffs and then butchering the carcasses. I know its instinctive to make it much more romantic and adventurous to vision the hunt with spears but the mass kill was really more productive and less dangerous
rudy says:
June 4, 2014 at 3:58 pm
Who says that humans did hunt the short-faced bear, lions or tigers. Perhaps they did, but just as likely they hunted out the prey of those animals.
That, along with climate change and other theories put forth in these comments was too much for some fauna and megafauna.
Sandi says:
June 4, 2014 at 3:31 pm
Yes, that was an organized slaughter with teams of men using fire-arms, with the intent of extirpating the buffalo to deprive the native peoples of a primary food source. The Passenger Pigeon was completely wiped out by hunters, some of them using cannon to fire birdshot at the vast flights of the doomed bird.
The survival up to that point of the large buffalo herds you cite is a strong argument against the idea of “…humans as the cause of the mass extinction of large animals all over the world during the course of the last 100,000 years.”
It may be that the same forces of nature that contributed to the demise of the megafauna also played a role in the movements and migrations of stone-age men. The famous,apparently flash-frozen mammoths date from this period, as do the seemingly wild climactic fluctuations of the YD.
agfosterjr says:
June 4, 2014 at 2:45 pm
Let me guess, you are that dude. Why not go ahead, be bold, and share with us this wondrous knowledge?
A couple of points. Many of the megafauna have vast ranges. Think of elephants and, yes, polar bears. Many, though not necessarily all, could have outpaced climate change. As to hunting, John Keegan made an interesting observation in his History of Warfare. Studies of our neolithic ancestors showed that a lot of them had injuries, such as broken bones, that are most similar to those of modern rodeo cowboys. This is suggestive of contact with large muscular animals.
Steve P says: (June 4, 2014 at 4:43 pm) “The survival up to that point of the large buffalo herds you cite is a strong argument against the idea of “…humans as the cause of the mass extinction of large animals all over the world during the course of the last 100,000 years.”
Nope, the example you cite is an argument in favor, because the buffalos’ herding behavior is a survival mechanism against being hunted, and the bigger the herds, the stronger was the hunting. This same mechanism is used by schools of fish to defend against sharks etc, and even people have used this mechanism, e.g. in the world wars the Allies ran their ships in large caravans to defend against the German submarine packs. That the buffalo herds were so huge shows that they were keenly hunted, but they adapted and survived whereas most other large mammals did not.
The Clovis people left and took the animals with them.
NZ Willy says:
June 4, 2014 at 5:11 pm
No doubt. But where do you draw the line between man and all the rest of the many hunters in the natural world, including some pretty nasty cursorial beasts on the scene long before the reputed arrival of H. sapiens?
This is special pleading: buffalo didn’t form protective herds until man came along.
Killing large animals is still a thrill, for some people. And would have been a rite of passage for young men. I bet they didn’t just eat the tender bits. Trophy heads, teeth, claws … are status symbols. There were all sorts of reasons for men to murder the megas.
The Glacial Maximum would have driven all fauna southwards into more predators and nicely concentrated them. Moreover, vegetation wasn’t robust and the competition for considerably less of it probably had an affect. I don’t have any problem with man having had a significant effect but I believe all factors associated with the glacial advance conspired. Imagine the Younger Dryas hitting suddenly when there had been relative plenty and wiping out vegetation forcing sudden distress (freezing, wiping out vegetation) of a large percentage of all fauna in the glaciated and nearby regions – this (like a frozen food store) probably gave enough food to more mobile and adaptable humans and other predators for them to get out of there. When they got further south, humans could eat something else – perhaps the wooly mammoth not so much. Was there a YD at the end of the other glaciations. No? Well there you go. That’s the difference.
I have no doubt that early humans could physically kill large animals. What I doubt is that their [early NA humans] numbers were great enough to put a significant dent in the megafaunal populations. Sure, they could harvest bison by running them off cliffs, or risk life and limb by poking mammoths with pointy sticks, but when all is said and done, in the time it took them to butcher and consume the animals, probably several times that total mass of bison or mammoth could have been added to the population. I just don’t think there were enough humans around to make a difference.
As an aside, look up Pleistocene Park and read about what they are doing in Eastern Siberia. http://en.m.wikipedia.org/wiki/Pleistocene_Park One of their projects involves DNA extraction from a Wooly Mammoth corpse.
It is amazing what a small trace animal can do.
James Strom says:
June 4, 2014 at 4:46 pm
Regarding the injuries, you’re confusing modern humans with Neanderthals. Don’t know if Keegan made that distinction or not. Moderns didn’t need to get as up close & personal with their prey because of their advanced projectile technology.
It doesn’t take many people to wipe out naive species, & the human population went through boom & bust in Clovis America. Megatons of meat, bone & hide were wasted, less of fat.
It has happened wherever our species has encountered isolated megafauna, & even microfauna, as on the Hawaiian Islands.
http://www.australiangeographic.com.au/news/2010/11/hunting-was-likely-killer-of-giant-marsupials/
milodonharlani, yes, and the remains of Moo spp found in NZ show that Maori took only the best cuts of meat and left the rest to rot, at least when they first arrived. They also brought domestic animals (dog and rat, at least, they actually raised them for food) which had a serious effect on the microfauna. The improved diet led to a population increase, when the moas disappeared Maori were reduced to eating each other, and ferns, at least away from the rich coastline.
Sandi says:
June 4, 2014 at 4:36 pm
Correct. The big predators died out because humans killed off the herbivores upon which they depended.
I am a skeptic, for these reasons, human populations in eurasia and the americas were never very large in prehistoric time and a continent is a pretty large place. It seems unlikely that there would not be some places which large animals could not have lived with no contact with humans. For this reason I discount the Maoris on New Zealand. That is a tiny place compared to a continent. (but I do not discount that setting fires changed the local flora. ). . Also to the person saying “Look at what happened to Buffalo populations” . Yes but that was with horses and firearms, not really an apt comparison. My own view is that stress caused by climate change and possibly disease caused extinctions to be well on the way by the time humans showed up to “finish the job”.
It is indisputable that man was responsible for the extinction of some large creatures, especially large birds, in more recent times. Besides the animals mentioned in other postings above, the moas (up to 13 feet tall) were wiped out within a century after New Zealand was settled by the Maori, and the elephant bird (weighing up to 1,000 pounds and laying eggs the size of a football)survived into the 1600s on Madagascar. And the last thylacine, or Tasmanian marsupial wolf, died in the 1930s.
I so want a mastodon steak right now. Properly aged and cooked over a fruit wood fire.
Thought Experiment:
Study the videos of the Chelyabinsk event of February 14, 2013.
Count the ‘Carolina Bays’ and other apparently time equivalent impact features in North America.
Review R.B.Firestone, et al – ‘Evidence for an extraterrestrial impact 12,900 years ago that contributed to megafaunal extinctions and the Younger Dryas cooling’. PNAS – October 9, 2007.
Read the descriptions of the Tunguska event of June 30, 1908.
Have another look at the Chelyabinsk videos. Estimate the applied energy of nearly simultaneous multiple Chelyabinsk ‘events’, including ‘near misses’ of the Tunguska type.
Contemplate the ‘impact’ of such an occurrence on the Clovis people as well as the megafauna.
Interesting?
JET
milodonharlani says:
June 4, 2014 at 6:22 pm
The reality is that game animals like bison and deer were abundant in N. America at the time of the arrival of the Europeans. The native people seemed to have killed as many as they could, and they did it year after year, until their system collapsed, and the tribes disintegrated.
And Africa’s vast herds of wildebeest, antelopes, zebras, and giraffes are not herbivores?
Yes humans may have caused the extinction of some species like wholly mammoths and saber-tooth cats. But we have created new breeds like dogs, cats, horses, cows, pigs, goats, sheep, camels, donkeys, etc. Without man there would be less biodiversity.
milodonharlani says:
June 4, 2014 at 6:22 pm
I would amplify that a bit by pointing out that “big predators” competed with humans for the herbivores that both preyed upon.
But the “big predators” also competed with humans for “safety” and shelter and water and campsites and dominance. Thus, while a human could tolerate living near bison or deer or moose or beaver, living near a cave bear (Europe) or the like was an immediate threat to the humans in a clan, with THEIR defenseless children in a vulnerable group. grizzlies, dire wolfs, saber-tooth tigers? Enemies. Not just “food” where you kill enough to eat what won’t spoil tomorrow.
So, the humans killed the large predators whenever they found them, went looking for more just in case and killed them as quickly and as efficiently as they could. It wasn’t simple competition in all cases, it was a vicious (and – for the humans – a successful) extermination campaign to save their lives. None of this “living in peace and joy” stuff.
Time? Well, Lewis and Clark crossed the entire continent twice in less than 4 years on foot and by boat with just about the same technology for transportation that the earliest humans had. Just walking and moving only in the summer months allows one group to cross the whole continent (one way) in two years. North-south would be 3-4 years to reach Panama – if somebody wanted.
Dr. Strangelove says: “Without man there would be less biodiversity.”
Oh please, what nonsense. There’s no reason to blame homo sapiens, as any species which attained our dominance would act the same, but the appearance of the dominant species has devastated the biodiversity. There used to be micro-biodiversities all over the world, where species developed and thrived in small places, all wiped out by mankind’s farming and other land & water management which bulldozes microclimates. I’m not being critical, just matter of fact Biodiversity is just a count of species. Ever heard of Stellar’s Sea Cows? Well here’s your clue — there’s a huge heap you’ll never hear of again.
Mcdonalds have used this strategy for years. Upsize for less!
Hi Geology Joe,
You don’t have to kill adult “elephant -sized” animals, you just need to kill their young.
Much smaller and easier to deal with.
And there is evidence of humans hunting adult mammoths.
Perhaps not many but maybe enough to tip the balance if the climate was changing.
https://www.sciencenews.org/article/ancient-siberians-may-have-rarely-hunted-mammoths
The Moas [12ft high flightless birds] were wiped out by the Maoris within about 100 years of their arrival in New Zealand.
And you can introduce competitors.
Aboriginal Australians introduced dogs to the continent which out competed the Tasmanian “Tiger” on the mainland. The remaining “Tigers” in Tasmania were finally wiped out by European settlers in the 1930s.