It's official: Humans were the leading cause of large animal extinctions

Scientists have long debated what caused the extinction of many large animal species over the past 50,000 years – humans or climate change. Recent research from Aarhus University’s ECONOVO Center concludes that human hunting played a significant role in megafauna extinctions. 

Decades of debate on megafauna extinctions 

“Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward,” wrote the study authors.

By examining fields such as extinction timing, dietary preferences, climate requirements, genetic population estimates, and hunting evidence, the researchers pinpointed human activity as a primary factor.

Human pressures were the key driver 

“Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence,” said the researchers.

“Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene.”

Climate change had a lesser impact

The climate changes of the Late Pleistocene did impact various species, but the most dramatic extinctions were primarily among large animals. 

“The large and very selective loss of megafauna over the last 50,000 years is unique over the past 66 million years,” said study lead author Jens-Christian Svenning, a macroecologist at Aarhus. This period saw no similar large-scale selective extinctions due to climate alone, indicating human influence was substantial.

Widespread megafauna extinctions 

Evidence shows early modern humans were effective hunters of large animals, leading to extinctions of mammoths and giant sloths worldwide. These extinctions happened at different rates and times but consistently followed the arrival of modern humans or significant cultural advancements. 

The extinctions occurred across all continents except Antarctica and in various ecosystems, from tropical forests to arctic environments. 

“Many of the extinct species could thrive in various types of environments. Therefore, their extinction cannot be explained by climate changes causing the disappearance of a specific ecosystem types,” noted Svenning.

Ecological consequences of megafauna extinctions 

The loss of megafauna has had significant ecological consequences, altering vegetation structures, seed dispersal, and nutrient cycling. Large animals play central roles in ecosystems, and their disappearance has led to profound changes in ecosystem structures and functions. 

“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,” said Svenning. This approach could mitigate the changes caused by the extinction of these large species and support the restoration of ecological balances.

The research incorporated various studies to present a comprehensive view of the extinctions, drawing on fields such as climate history, vegetation history, fauna evolution, and archaeological data on human expansion and lifestyle. 

This interdisciplinary approach provided a broader understanding of the factors contributing to the loss of megafauna. 

Proactive measures to protect large species 

The study underscores the importance of considering human impact on these extinctions and the need for proactive measures to protect remaining large species and restore ecological health.

“A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning,” noted the researchers.

“The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning.” 

“Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings.”

The research is published in the journal Cambridge Prisms: Extinction,

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