Humans might be responsible for megafauna extinctions after all

Humans or climate change? Debate has raged for decades over which of these factors led to the extinction of the Ice Age megafauna which were once widespread on every continent except Antarctica.

But now a review article analysing existing research from over the years claims that the decline of megafauna can most probably be attributed to hunting by ancient humans.

The peer-reviewed review is published in the journal Cambridge Prisms: Extinction.

Greater the size, greater the fall

Megafauna are any animal – mammal, bird, reptile – weighing more than about 45kg, about the same as a grey wolf.

According to the fossil record, at least 161 species of large mammal were driven to extinction in the past 50,000 years.

Graphic showing increasing animal size and the level of extinction
This figure shows extinction of large mammals during the late Quaternary period (2.58 million years ago to today) related to body size. TOP: Global percentage of species that went extinct based on their size. BOTTOM: Break down by continent. The black numbers represent the total number of species that lived during this time. The red numbers show the number that went extinct. Credit: Aarhus University ECONOVO / Cambridge Prisms: Extinction

The worst hit megafauna were the giant land-dwelling herbivores like woolly mammoths. The fossil record shows that globally 50,000 years ago, there were 57 species of these megaherbivores which weighed more than a tonne. Today, only 11 remain. And these 11 have also seen drastic population decline.

In Australia, no animal larger than 100kg survived past the end of the last Ice Age about 12,000 years ago. While some researchers maintain there is no evidence linking indigenous people in Australia to the extinction of megafauna, the same cannot be said globally.

Climate culprit?

Because of the dramatic shifts in the global climate which led to the thawing at the end of the Ice Age, many scientists have argued that climate change must have been the primary driver of the megafauna extinctions.

While climatic shifts affected populations of animals of all sizes in the Late Pleistocene (~130,000 to 11,700 years ago), significant extinctions were only seen among the biggest.

And the authors of the new study say that the climatic impacts can’t account for the scope of the megafauna losses.

Their analysis considers previous research on climate and vegetation history over the past 1–3 million years, animal evolution over the past 66 million years, and archaeological studies on human expansion, lifestyle and diet.

“The large and very selective loss of megafauna over the last 50,000 years is unique over the past 66 million years,” says lead author Jens-Christian Svenning, a professor at Aarhus University in Denmark. “Previous periods of climate change did not lead to large, selective extinctions, which argues against a major role for climate in the megafauna extinctions.”

“Another significant pattern that argues against a role for climate is that the recent megafauna extinctions hit just as hard in climatically stable areas as in unstable areas,” Svenning adds.

Ancient whodunit

There is clear archaeological evidence that ancient humans did hunt megafauna. This includes the discovery of traps designed for large animals and analyses of human bones and residue from spear points which show they hunted and ate the biggest animals.

Illustration of ice age hunters trying to capture a mammoth, also showing the use of mammoth skin for shelter, and roasting of mammoth meat - stock illustration
Credit: Dorling Kindersley / Dorling Kindersley RF / Getty Images Plus.

“Early modern humans were effective hunters of even the largest animal species and clearly had the ability to reduce the populations of large animals,” Svenning. “These large animals were and are particularly vulnerable to overexploitation because they have long gestation periods, produce very few offspring at a time, and take many years to reach sexual maturity.”

In some parts of the world, the demise of megafauna was quick. In others, it took more than 10,000 years for the large animals to die out.

Large animals play a central role in ecosystems, particularly in influencing vegetation structure, seed dispersal and nutrient cycling.

“Our results highlight the need for active conservation and restoration efforts. By reintroducing large mammals, we can help restore ecological balances and support biodiversity, which evolved in ecosystems rich in megafauna,” says Svenning.

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