Humans were responsible for the extinction of large mammals

The debate has raged for decades: Was it humans or climate change that led to the extinction of the many species of large mammals, birds and reptiles that have disappeared from Earth over the past 50,000 years?

By “big,” we mean animals that weighed at least 45 kilograms—known as megafauna. At least 161 mammal species were driven to extinction during this period. This number is based on the remains found so far.

The biggest of them were hit hardest—the ground-dwelling herbivores weighing over a ton, the megaherbivores. Fifty thousand years ago, there were 57 species of megaherbivores. Today, only 11 remain. These 11 remaining species have also seen their populations decline drastically, but not to the point of complete extinction.

A research group from the Danish National Research Foundation’s Center for Ecological Dynamics in a New Biosphere (ECONOVO) at Aarhus University now concludes that many of these extinct species were hunted to extinction by humans.

They present this conclusion in an invited review article published in the journal Cambridge Prisms: Extinction. A review article synthesizes and analyzes existing research within a particular field.

In this case, researchers from Aarhus University incorporated several research areas, including studies directly related to the extinction of large animals, such as:

• Time of species extinction
• Dietary preferences of animals
• Climate and habitat requirements
• Genetic estimates of past population sizes
• Evidence of human hunting

Moreover, they included a wide range of studies from other fields necessary to understand the phenomenon, such as:

• Climate history over the last 1-3 million years
• Vegetation history during the last 1-3 million years
• Evolution and dynamics of fauna during the last 66 million years
• Archaeological evidence of human expansion and lifestyle, including dietary preferences

Climate change played a smaller role

Dramatic climate changes during the last interglacial and glacial periods (known as the Late Pleistocene, from 130,000 to 11,000 years ago) certainly affected the populations and distributions of large and small animals and plants around the world. However, significant extinctions were observed only among large animals, especially the largest ones.

An important observation is that earlier, equally dramatic ice ages and interglacials during the last two million years did not cause a selective loss of megafauna. Especially at the beginning of the ice ages, the new cold and dry conditions caused large-scale extinctions in some regions, such as trees in Europe. However, there was no selective extinction of large animals.

“The large and highly selective loss of megafauna over the past 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 extinctions.” megafauna,” says Professor Jens-Christian Svenning. He runs ECONOVO and is the lead author of the article.

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

Effective hunters and vulnerable giants

Archaeologists have found traps designed for very large animals, and isotope analyzes of ancient human bones and protein residue from spear points show that they hunted and ate larger mammals.

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

The analysis shows that human hunting of large animals such as mammoths, mastodons and giant sloths was widespread and consistent around the world.

It also shows that species went extinct at very different times and at different rates around the world. In some local areas, this happened fairly quickly, while in other places it took over 10,000 years. But everywhere, it happened after modern humans arrived, or in the case of Africa, after cultural advances among humans.

Species became extinct on all continents except Antarctica and in all types of ecosystems, from tropical forests and savannas to Mediterranean and temperate forests and steppes to arctic ecosystems.

“Many of the extinct species can thrive in different types of environments. Therefore, their extinction cannot be explained by climate change causing the extinction of a specific type of ecosystem, such as the mammoth steppe, which also housed only a few species of megafauna ,” he explains. Svenning.

“Most species existed in temperate to tropical conditions and should have actually benefited from warming at the end of the last ice age.”

Implications and recommendations

The researchers point out that the loss of megafauna has had profound ecological consequences. Large animals play a central role in ecosystems by influencing vegetation structure (eg the balance between dense forest and open areas), 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 into megafauna-rich ecosystems,” says Svenning.