For decades, the question has loomed large: what caused the extinction of numerous species of large mammals, birds, and reptiles over the past 50,000 years? Defined as animals weighing at least 45 kilograms or megafauna, a minimum of 151 mammal species vanished during this period, based on the discovered remains.
The megaherbivores – land-dwelling herbivores weighing over a ton – suffered the most significant blows. Fifty thousand years ago, 57 species of megaherbivores existed, and today only 11 remain. The surviving 11 species have also experienced severe population declines, although not to the point of complete extinction.
A research team from the Danish National Research Foundation’s Center for Ecological Dynamics (ECONOVO) at Aarhus University has now reached the conclusion that human hunting led to the extinction of many of these vanished species.
During the late Pleistocene period, spanning from 130,000 to 11,000 years ago, significant changes in climate had a profound impact on the global distribution of both large and small animals as well as plants. It is noteworthy that while these dramatic climate shifts led to the extinction of numerous large animals, particularly the largest ones, smaller animals and plants were not as significantly affected.
Interestingly, previous ice ages and interglacial periods occurring over the past few million years did not result in the same selective loss of large animals. Although the onset of glacial periods did lead to widespread extinctions in certain regions, such as trees in Europe, large animals did not experience selective extinctions during these periods.
“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,” says Professor Jens-Christian Svenning. He leads ECONOVO and is the lead author of the article. He adds, “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.”
Ancient humans were skillful hunters, capable of effectively targeting and consuming the largest mammal species. Their hunting activities resulted in a significant reduction in the populations of these large animals. Vulnerable due to their long gestation periods, low offspring production, and extended time to reach sexual maturity, these large animals were greatly affected by human activities.
This figure shows how the extinction of large mammals during the late Quaternary period is related to their body size. At the top, you can see the global percentage of species that went extinct based on their size. The bottom part breaks it down by continent. The black numbers represent the total number of species that lived during this time, including those that are still around and those that have gone extinct. The red numbers show the species that went extinct. Credit: Aarhus University ECONOVO / Cambridge Prisms: Extinction
The analysis further indicates that human hunting of mammoths, mastodons, and giant sloths was widespread across the globe. The extinction of these species occurred at varying times and rates globally but consistently followed the arrival of modern humans or cultural advancements among humans in Africa.
The extinction of species has occurred on all continents except Antarctica and across various ecosystems. Even species capable of adapting to different environments have disappeared, indicating that their extinction cannot be solely attributed to climate changes.
The researchers point out that the loss of these megafauna species has significantly impacted ecosystems, leading to changes in vegetation, seed dispersal, and nutrient cycling. Their disappearance has resulted in significant 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,” says Jens-Christian Svenning.
Journal reference:
Jens-Christian Svenning et al. The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene. Cambridge Prisms: Extinction (2024). DOI: 10.1017/ext.2024.4
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