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.
Udar says:
June 4, 2014 at 1:12 pm
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….
What you really want to stop and think about is digging a hole big enough for an elephant. Now that would be a hole. Archaeological evidence seems to suggest that pits were mostly reserved for small animals and insects. Bigger ones, known from Scandinavia, are mostly later Neolithic and Bronze Age. The chief determinants of a pit are 1) tools, 2) soil depth, and 3) soil type. I hesitate to argue that Ice Age pit traps are unknown, but I’ve never heard of them out side fiction. Second, while really big earth works do appear in Turkey for instance very early (12 kya), they are not common elsewhere. Then of course, the soil has to be deep enough, even if you have tools that are up to the work. There just are not that many places around the planet where the hunter can say, “let’s dig a huge hole and trap a mammoth.”
The chief evidence of human predation on mammoths comes from western Siberia and Eastern Europe where some Pleistocene villages with houses built of mammoth bone (seems straight out of Edgar Rice Burroughs) have been excavated. There are “suggestive” associations in the Americas, but they aren’t iron clad by any stretch. More importantly, “megafauna” – i.e. elephants, rhinos, hippos, etc., survived in Africa just fine until rifles and a hunger for ivory arrived historically. Megafauna vanish where suitable habitats were yanked out from under them by the rapid changes at the end of the Pleistocene and even then bison for instance survived in N. America again until horses and guns changed the rules. Horses vanished, but that may be due to disease since they like the same kinds of environment bison do. In fact, even in the Americas, the only evidence of wholesale wasteful hunting is post-Pleistocene and only includes bison. Occasionally hundreds of animals would be run over “jumps” – no pits mind you – and humans proceeded to butcher all they could.
milodonharlani says:
June 5, 2014 at 11:09 pm
…
Good point, so to speak.
Not really. Haynes has not and, given what little evidence we really have, cannot offer a sound statistical argument. His argument is hand waving and being enamoured by a “neat” idea that became fashionable in archaeology following the publications of pessimistic views of human effects by Ehrlichman and the Club of Roman. By and large the reasoning Haynes uses is equivalent to that which supports the idea of “ley lines.”
Wow, you really butchered those.
You are right Duster, deer were hunted by early UK immigrants. The buffaloo jumped over a cliff, and they were scavenged, but there is an example of a baby or young mammoth, being cornered in a canyon, separated from the herd, and killed. They threw rocks on it from above. The Lascaux cave paintings too indicate that they had some megafauna left 37,000 years ago. But archaeologists don’t know why they were painted, wishful thinking or a hunting belief?
Steve P,
You may well be right about hunting, and have given me much food for thought.
One way man may have amplified his affect was through use of fire. Large areas were burned regularly by indigenous peoples in order to promote certain types of useful plant growth and habit for certain wildlife. I would not be surprising if some animal species would have gone extinct in this environment while others thrived. That was the whole point.
lokenbr I don’t buy this
“promote certain types of useful plant growth and habit for certain wildlife”
All the Australian aborigines were doing was “killing and cooking” anything in their immediate vicinity.
Simply, another case of funded fantasy PC running rife.
Deer, bear and elk, as noted, were not exterminated, and they were plenty wary of humans, as were buffalo. The accounts I’ve quoted above make that clear. The naive prey species idea doesn’t fly as a rational explanation for the Late Pleistocene extermination event.
The body parts of deer, bear, and elk festoon native regalia, and were used also for clothing, tools or weapons. Generally speaking, the lack of remains can be explained by the fact that the native peoples used everything from the creatures they killed. Anything left behind would have been dragged off and/or consumed by scavengers like the coyote.
cnxtim,
Well, I won’t try to sell you on it.
Either way, fire is an effective way too wipe out a lot of wildlife.