Scientists have discovered that human hunting, rather than climate change, was the main driver behind the extinction of megafauna – large animals like elephants, mammoths and rhinoceroses – over the past 50,000 years.

The study, conducted by the Danish National Research Foundation's Center for Ecological Dynamics in a Novel Biosphere at Aarhus University, was published in March in the journal Cambridge Prisms: Extinction. 

By synthesizing and analyzing existing research within several fields, including the timing of species extinctions, the animals' dietary preferences, climate and habitat requirements, genetic estimates of past population sizes and evidence of human hunting, the researchers conclude that many of the vanished species during the time period were hunted to extinction by humans.

During this period, at least 161 large mammal species went extinct based on recovered remains. Megaherbivores, the largest land-dwelling herbivores over 1,000 kilograms in weight, were particularly impacted. Fifty thousand years ago, there were 57 megaherbivore species; today, only 11 survive, with significant population declines.

The research points out that previous ice ages and interglacials over the past couple of million years did not cause a selective loss of megafauna. While new cold and dry conditions at the start of glacial periods led to large-scale extinctions in some regions, such as trees in Europe, large animals did not face selective extinctions.

"The large and very selective loss of megafauna over the last 50,000 years is unique over the past 66 million years. Previous periods of climate change did not lead to large, selective extinctions, which argues against a major role for climate in the megafauna extinctions," said Jens-Christian Svenning, the lead author of the article. "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," he added.

Instead, the archaeological evidence, such as traps designed for large animals and protein residues from spear points, shows that early humans extensively hunted large animals, which were vulnerable due to long gestation periods, low reproductive rates and slow maturation, leading to the extinction of species like mammoths, mastodons and giant sloths.

The decline of large mammals has deeply altered ecosystems, impacting vegetation, seed dispersal and nutrient cycles. 

The researchers stress active conservation and restoration efforts, saying that reintroducing large mammals can restore ecological balances and support biodiversity, which is crucial for ecosystems that evolved with abundant megafauna.