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 became extinct during this period. This number is based on the remains found so far.

The biggest of them were hit the hardest – the over a ton land-dwelling herbivores, the mega-herbivores. Fifty thousand years ago, 57 species of megaherbivores lived here. Today, only 11 remain. The remaining 11 species have also seen their populations decline drastically, but not to the point of extinction.

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

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

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

• The timing of species extinction
• Dietary preferences of animals
• Climate and habitat requirements
• Genetic estimates of past population size
• Evidence of human hunting

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

• Climate history over the past 1–3 million years
• Vegetation history over the past 1–3 million years
• Faunal evolution and dynamics over the past 66 million years
• Archaeological data on human expansion and lifestyle, including dietary preferences

Climate change played a lesser role

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

An important observation is that previous, equally dramatic ice ages and interglacials over the past few million years did not cause selective declines in megafauna. Especially at the beginning of the ice ages, new cold and dry conditions caused widespread die-offs in some regions, such as trees in Europe. However, there was no selective extinction of large animals.

“The large and highly selective decline of megafauna in the last 50,000 years is unique in the last 66 million years. Previous periods of climate change did not lead to large, selective extinctions, which argues against a major role of climate in the extinction of megafauna,” says Professor Jens-Christian Svenning. He leads ECONOVO and is the main author of the article.

He adds: “Another significant pattern that argues against a role for climate is that recent megafauna extinctions have hit climate-stable areas as hard as unstable areas.”

Effective hunters and vulnerable giants

Archaeologists have found traps designed for very large animals, and isotopic analyzes of ancient human bones and protein residues from spearheads show that they hunted and ate the largest mammals.

Svenning adds: “Early modern humans were efficient hunters of even the largest 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 long gestation periods and produce very few offspring.” at once and takes 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 throughout the world.

It also shows that the species died out at very different times and at different rates around the world. In some local areas this happened quite quickly, while in others it took over 10,000 years. But everywhere it happened after the arrival of modern humans, or in the case of Africa, after cultural progress among humans.

Species became extinct on every continent except Antarctica and in every type of ecosystem, from tropical forests and savannas to Mediterranean and temperate forests and steppes to arctic ecosystems.

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

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

Implications and recommendations

Scientists point out that the loss of megafauna had profound ecological consequences. Large animals play a central role in ecosystems by influencing vegetation structure (eg, the balance between dense forests and open areas), seed dispersal, and nutrient cycling. Their disappearance resulted in significant changes in the structures and functions of ecosystems.

“Our results highlight the need for active conservation and restoration efforts. By reintroducing large mammals, we can help restore the ecological balance and support the biodiversity that has evolved in megafauna-rich ecosystems,” says Svenning.