Were humans the reason that the megafauna went extinct?

Was it climate change or humans that caused the unfortunate extinction of large mammals, reptiles and birds over the last 50,000 years?

Etching of humans hunting a mammoth
Prehistoric humans hunt a woolly mammoth. Credit: Engraving by Ernest Grise, photographed by William Henry Jackson. Courtesy Getty's Open Content Program.

Over the last 50,000 years at least 161 species of large animals, known as megafauna, have become extinct. The largest of these creatures were hit the hardest, the megaherbivores. Megaherbivores weighed over a tonne, and 50,000 years ago around 57 species were roaming the Earth. Now, only 11 remain.

A research team from the Danish National Research Foundation’s Centre for Ecological Dynamics in a Novel Biosphere (ECONOVO) at the University of Aarhus, has concluded that many of these species were hunted to extinction by humans in a review article published in the journal Cambridge Prisms: Extinction.

For this review, the researchers used several research fields, including studies that discuss issues relating to the extinction of large animals such as the timing of species extinctions, climate and habitats, and evidence of human hunting. In addition to this, they also included studies from other fields that would help to understand the extinctions such as the Earth's climate history over the last 1-3 million years, and archaeological data on human expansion and dietary preferences.

Extinctions influenced by the Ice Ages?

Climate change throughout the last glacial and interglacial periods during the Late Pleistocene (130,000 – 11,000 years ago) would have also affected the population of large and small animals worldwide. However, significant extinctions were only seen among the large animals, particularly the largest species.

However, during the previous ice ages and interglacials over the last few million years, selective loss of megafauna was not observed. The beginning of the glacial periods, where it became drier and colder, brought about large-scale extinctions in some regions. However, there were no large-scale extinctions seen within the megafauna.

"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 the lead author Professor Jens-Christian Svenning. "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."

Hunted by Humans

Archaeologists have found evidence of traps designed for very large animals as well as isotope analysis of human bones and spear points showing evidence that humans killed and ate large mammals, such as mastodons, mammoths, and giant sloths. Professor Svenning states, "Early modern humans were effective hunters of even the largest animal species and had the ability to reduce the populations of large animals. 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."

The review also shows that species all went extinct at different times and at different rates across the world. In some areas, it happened quickly, while in others it took 10,000 years. However in all cases, it happened after modern humans arrived, or in the case of Africa, after cultural advancements among humans.

Species went extinct across all of the continents apart from Antarctica and across a variety of ecosystems. "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 type, such as the mammoth steppe – which also housed only a few megafauna species," explained Svenning. "Most of the species existed under temperate to tropical conditions and should have benefited from the warming at the end of the last ice age."

The research team has concluded that the loss of the megafauna had profound ecological consequences, as the large animals played an important role in the ecosystem by influencing the vegetation structure, dispersal of seeds, 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," said Svenning.

Source of the news:

Svenning, J.-C., Lemoine, R.T., Bergman, J., Buitenwerf, R., Roux, E.L., Lundgren, E., Mungi, N. and Pedersen, R.Ø. (2024). The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene. Cambridge Prisms: Extinction, [online] 2, p.e5.

doi:https://doi.org/10.1017/ext.2024.4.