Around 50,000 to 10,000 years ago, the Earth lost many of its largest animals.
These were not just slightly bigger versions of today’s wildlife, but true giants.
There were saber-toothed cats with long, knife-like teeth, massive sloths as large as elephants, woolly mammoths with huge curved tusks, and even wombats the size of small cars.
After surviving for millions of years, most of these large animals suddenly vanished.
A new study published in Proceedings of the National Academy of Sciences shows that their disappearance did not just remove a few species.
It changed entire ecosystems in ways that are still visible today, especially in the Americas.
When a species goes extinct, the impact does not stop there. Animals are connected through food webs, which describe who eats whom.
If one species disappears, it can affect many others. For example, if a top predator vanishes, its prey may increase rapidly, which can then affect plants and other animals. These chain reactions can reshape the whole system.
The research team, led by Lydia Beaudrot, wanted to understand how the loss of large mammals long ago still influences ecosystems today.
To do this, they analyzed data from 389 locations across tropical and subtropical regions in the Americas, Africa, and Asia. The study included more than 440 mammal species, such as lions, wolves, elephants, and bears.
All ecosystems have similar basic structures, with predators, prey, and plants forming different levels in a food web.
However, the number and type of species can vary greatly between regions. The researchers found that food webs in the Americas look quite different from those in Africa and Asia.
In the Americas, there are fewer large prey animals, and most of the remaining prey species are smaller.
Predators in these regions also tend to hunt a narrower range of animals. In contrast, Africa and Asia still have more large animals, which allows for more complex and diverse food webs.
These differences are not just due to modern factors like climate or habitat. Instead, the study shows that they are strongly linked to what happened thousands of years ago.
The Americas experienced especially severe losses during that time, losing more than 75 percent of mammals weighing over 100 pounds.
For example, South America once had many large herbivores, such as giant deer. When these animals disappeared, predators lost important food sources. As a result, the food web became simpler and less connected.
Scientists still debate why these giant animals went extinct. Some believe climate changes played a major role, while others point to the spread of humans and hunting pressure. It is likely that a combination of factors was involved.
Understanding these ancient changes is important today because many large mammals are once again at risk. According to the International Union for Conservation of Nature, nearly half of mammals weighing more than 20 pounds are now threatened with extinction.
This study suggests that losing large animals can have long-lasting effects that ripple through ecosystems for thousands of years. By studying the past, scientists hope to better predict what might happen if today’s threatened species disappear, and how to protect the balance of nature before it is too late.
