Did our ancestors really drive Ice Age animals to extinction?

The true cause behind the Quaternary extinction event – the worldwide phenomenon that wiped out 177 species of mammalian megafauna a hundred millennia ago – has eluded science for the longest time.

While popular hypotheses identify either climate change or the rise of humanity as the factor that truly spelled doom for the woolly mammoth, the smilodon, and their ilk, researchers have spent the last five decades trying to determine the real reason behind the extinction of the gigantic creatures that dominated the global Plio-Pleistocene landscape.

 

 

However, researchers from Aarhus University believe that they have evidence strong enough to uncover the truth – and it may be a rather uncomfortable one.

 

Hunting for answers

 

Led by Aarhus’s Professor Jens-Christian Svenning, the study, which was recently published in the Proceedings of the Royal Society, points to the boom in global human activity – both in terms of expansion and hunting – as the main reason behind the disappearance of mammalian species that weighed more than or equal to 10 kg (22 lbs) existing between 132,000-1,000 years ago.

 

The so-called “overkill” theory suggests that Ice Age animals were unable to cope with the effects of humanity’s migration from Africa to different continents over the last 100,000 years. The study’s findings provide a strong correlation between human hunting and extinction. Large prehistoric animals (or in the case of carnivores, their smaller prey) were hunted by humans for food; rapidly dwindling populations and food source scarcity soon led to the Ice Age animals’ extinction.

 

By mapping the geographical variation of mammalian megafauna that existed during the Quaternary extinction event’s time frame, the researchers found that massive species wipeouts occurred in virtually all climate zones, affecting cold-adapted, tropical, and temperate species alike. Out of the 177 species that went the way of the dinosaurs, 62 species were from South America, 43 were from North America, 38 came from Asia, 26 from Australia and its surrounding region, 19 from Europe, and 18 from Africa. The largest losses were observed in North and South America, where saber-toothed cats, mastodons, giant armadillos, and giant sloths used to be widespread.

 

“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),” explained Svenning. “In general, at least 30% of the large species of animals disappeared from all such areas.”

 

“Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals,” according to study co-author Søren Faurby.

 

Climate change – a cold theory?

 

The climate change theory, on the other hand, takes into account the effects of warmer global temperatures on animals who may have been unable to adapt to the climate shift. However, the researchers’ findings on the various species of megafauna that went extinct during this time period only suggest a weak link between climate change and extinction in nearly all regions (save for Eurasia).

 

Lead author Christopher Sandom cited reindeer and polar foxes as an example; while they initially inhabited central Europe, they moved to the colder north as the area became warmer. “The significant loss of megafauna all over the world can therefore not be explained by climate change,” said Sandom, who instead affirmed that climate change played a key role in changing species distributions across the world.

 

Interestingly, a study published in Nature this year analyzed 10,000-year old sediments, as well as gut and coprolite samples from Ice Age mammals. According to the study, it was the major loss of plant diversity and protein-rich forbs (herbaceous flowering plants) due to the climate shift that led to the extermination of herbivorous North American and Asian species.

 

The agents of extinction

 

While science may still be a long way from definitively concluding what truly exterminated the Ice Age animals, humanity’s track record over the last few centuries does not exactly paint an optimistic picture for our future. The dodo bird, the West African black rhinoceros, the Caribbean monk seal, and the great auk are just a few examples of creatures that were eradicated by humanity’s hand.

 

As more and more species are nearing extinction thanks to ruthless hunting, poaching, forest razing, pollution, overfishing, and a regrettable ignorance – or wanton disregard – of deteriorating environmental conditions and population numbers, one has to wonder: how many more species need to disappear from the face of the planet before humanity realizes that it may simply be repeating mistakes from a hundred thousand years ago? — TJD, GMA News