Between 50,000 and 10,000 years ago, many of the world's largest mammals disappeared. Picture creatures like saber-toothed cats with 7-inch fangs and elephant-sized sloths. Woolly mammoths whose curved tusks grew longer than 12 feet. Even a 3-ton wombat the size of a car. After roaming the Earth for millions of years, most large-bodied mammals — especially those weighing over a ton — were wiped out. Vanished.
A new study reveals how their disappearance fundamentally reshaped food webs for the species that remain today, and why the changes were more pronounced in some parts of the world than others, particularly in the Americas.
The results will appear April 27 in the journal Proceedings of the National Academy of Sciences.
When any species goes extinct, it's not just the animal that vanishes — the web of relationships among the surviving species often shifts in complex ways too.
When predators disappear, their prey can multiply unchecked, causing a series of cascading effects, said senior author Lydia Beaudrot , an assistant professor of integrative biology and member of the Ecology, Evolution & Behavior program at Michigan State University.
Beaudrot had a hunch based on some of her previous research that the extinction of large mammals tens of thousands of years ago could have had long-lasting effects on food webs — the often complex networks of who eats whom.
"But there weren't that many data points," she said.
So Beaudrot and colleagues set about developing methods for synthesizing more data at larger spatial scales. For the new study, a team led by Beaudrot and first author Chia Hsieh analyzed recent data on predator-prey relationships at 389 sites across tropical and subtropical regions of the Americas, Africa and Asia.
The study included more than 440 species of mammals including bears, wolves, elephants and lions.
Food webs throughout the world all have the same basic trophic levels: animals that eat and are in turn eaten by others. However, the number and types of species vary greatly between different areas.
Overall, they found that food webs today have fewer, smaller prey in the Americas than in Africa and Asia.
And when they looked at prey characteristics such as body mass and activity patterns, they found that predators in the Americas stuck to prey with a narrower range of traits, with less overlap among them.
The differences among regions didn't just stem from current factors such as weather or the seasons, said Hsieh, who is a Presidential Postdoctoral Fellow in MSU's Ecology, Evolution, and Behavior program.
Rather, they found that differences in the severity of past extinctions played a significant role.
Each region suffered their share of losses. But the Americas got hit the hardest, losing more than three-quarters of all mammals over 100 pounds during the last 50,000 years.
For example, South America was once home to several giant deer. Their extinction left fewer prey for predators such as saber-toothed cats and dire wolves, essentially flattening and thinning out the food web.
"A lot of the lower part of the food web was lost," Hsieh said.
Just why the most massive mammals disappeared is still a subject of debate.
Some scientists say climate and environmental stresses played a role in the loss of mammoths and other giants. Others say the spread of humans out of Africa to other parts of the world is to blame for their demise.
But whatever their cause, the new study confirms that their disappearance has had long-lasting consequences.
The research is important because it helps scientists understand the potential long-term impacts of species facing extinction today.
Around the planet, nearly half of all mammals weighing more than 20 pounds are considered vulnerable, endangered or critically endangered by the International Union for the Conservation of Nature (IUCN).
As a next step, Beaudrot said, the team plans to look at whether historical extinctions could make certain communities more vulnerable going forward.
"By studying the past, we can also try to understand what to expect in the future," Hsieh said.
This research was supported by the U.S. National Science Foundation (DEB-2213568), Rice University, and a Michigan State University Presidential Postdoctoral Fellowship in Ecology, Evolution, and Behavior.
CITATION: "Historical legacies shape continental variation in contemporary mammal food webs," Chia Hsieh, Evan C. Fricke, Wei-Hao Lee, Daniel Gorczynski, Lydia Beaudrot. Proceedings of the National Academy of Sciences, April 27, 2026. DOI: 10.1073/pnas.2519938123
