While history might have been inclined to blame the mass extinction of some of the Earth's mightiest mammals on climate change, scientists suggest a likelier culprit.
For decades, the circumstances surrounding the disappearance of large mammals — some 177 species vanished in the wake of the last Ice Age — has been hotly contested.
Dubbed megafauna, the list of the missing is staggering. According to scientists at Denmark's Aarhus University, woolly mammoths, forest elephants, giant deer and even some species of giant sloths are among the missing — representing big mammals from almost every climate zone.
Skeleton of Megatherium, extinct giant ground sloth of South America: herbivore. This specimen found in Paraguay c1796. Lithograph published London 1823 (Photo by Universal History Archive/Getty Images)
As recently as 2013, scientists at the University of Cincinnati were confidently proclaiming, "The climate changed rapidly and profoundly. And coinciding with this very rapid global climate change was mass extinctions."
Not so, Danish researchers contend in a freshly published research paper.
“Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals,” notes Søren Faurby, a postdoctorate researcher at Aarhus.
The researchers point out that periods of dramatic climate swings characterized each Ice Age, with the most recent epoch spanning from around 110,000 to 12,000 years ago. What puzzled scientists, however, was the absence of mass extinctions during previous Ice Ages.
"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," suggests Aarhus researcher Christopher Sandom.
"Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer."
Story continues after slideshow.
PHOTOS: GIANT PREHISTORIC ANIMALS, 'MEGAFAUNA'
So why did the last swing of the climate pendulum coincide with the ravaging of Earth's big mammals?
Well, it may have something to do with a relatively new animal on the block.
What we regard as modern man first appeared in Africa, before touching down on fresh continents — a migration that only really took hold over the last 100,000 years.
The Danish study, hailed as the first worldwide analysis of large animals living between 132,000 and 1,000 years ago, found a compelling correlation between human expansion and vanishing mammals.
"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 Aarhus professor Jens-Christian Svenning, who also worked on the study.
So, where have all the giant kangaroos, giant wombats and marsupial lions gone?
The Danish research points to one stark conclusion.
They likely met the end of the evolutionary line at the tip of a hunter's spear.
And an even more chilling forecast for today's large animal population.
The study notes:
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).