Did Humans, Not Climate Change, Trigger Ice Age Animal Extinctions?
It’s a debate that has raged for almost half a century. What exactly caused so many large mammals to die out right around the end of the last Ice Age? A prevailing theory holds that climate change caused massive loss of suitable habitat, leading to widespread extinctions.
A new study disagrees. Apparently, the evidence points not toward Mother Nature, but squarely at the human race, according to researchers from Denmark’s Aarhus University.
For the first time, researchers undertook what they called a “global analysis and relatively fine-grained mapping of all the large mammals (with a body weight of at least [22 lbs.]) that existed during the period 132,000–1,000 years ago – the period during which the extinction in question took place.”
They focused with more precision than any previous study on the percentages of large animals that became extinct in various geographic locales. What they found is striking.
That Last Ice Age: For Animals, Different Than the Rest
More than one Ice Age has gripped the Earth over the millenia. Our planet has seen at least five major Ice Ages, in fact — the Huronian, the Cryogenian, the Andean-Saharan, the Karoo, and the most recent, known as the Quaternary or Pleistocene glaciation. What’s interesting is that only after the last one did we see significant extinction of large animals, according to this study.
The study results indicate only a minimal correlation between temperature and precipitation changes and the significant loss of so many great mammals.
“The significant loss of megafauna all over the world can therefore not be explained by climate change,” said Christopher Sandom, Aarhus University Postdoctoral Fellow, “even though it has definitely played a role as a driving force in changing the distribution of some species of animals.”
As it turns out, 177 different species of large mammals died out during the most recent Ice Age. The losses during this period spread out relatively evenly among continents, as follows:
- Africa: 18 species
- Europe: 19 species
- Asia: 38 species
- Australia and surrounding areas: 26 species
- North America: 43 species
- South America: 62 species
These extinctions occurred in almost all climate zones, affecting animals suited to cold, temperate and tropical climates alike. Australia lost creatures such as giant kangaroos, marsupial lions and giant wombats. Europe and Asia lost great elephants, rhinoceroses and giant deer. In North and South America, sabre-toothed cats, mastodons, giant sloths and giant armadillos went extinct.
Where Humans Go, Extinctions Follow
The fact that so many animals from such varied habitats all died out during roughly the same period correlates rather neatly with the footprint of ancient humankind as we spread out across the world.
The study’s results show “a very strong correlation between the extinction and the history of human expansion,” noted an Aarhus University press release.
“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,” said Professor Jens-Christian Svenning. “In general, at least 30 percent of the large species of animals disappeared from all such areas.”
It’s a scenario we know all too well. Humans show up to a new and untouched region and begin hunting. We take down the great mammals. We even hunt their prey. At some point, we go too far. It’s a phenomenon known as “overkill.” Sound familiar?
It seemed that way to the researchers, too. They note a definite similarity between what humans did 100,000 years ago and what we’ve done in the recent past to animals such as the American bison, the European bison, the quagga and the Eurasian wild horse.
We’re still doing the same old thing today, as poachers busily decimate already rare species such as elephants, rhinoceroses and big cats, to name only a few. This is not the cycle of life, as it may have been once upon a time. Today, extinction is often caused by pure and simple greed.
Interesting, isn’t it? Even ages ago, the influence of humankind profoundly affected animals. We can’t really blame early man, of course — he was just trying to survive. What’s our excuse today?
Photo credit (all images): Thinkstock