Climate change decided who ruled as top predator 35 million years ago
A new study on European fossils reveals strong changes in body mass in predatory mammals occurred mainly after major environmental shifts
image:
Evolution of temperature (top) and body mass of carnivoramorphans (middle) and hyaenodonts (bottom) across the Paleogene.
view moreCredit: ULiège Valentin Fischer
An international team of researchers from Belgium, France, Switzerland, Spain, and the USA has reconstructed the evolution of body mass in carnivorous mammals during the Paleogene – a crucial window in the diversification of mammals, that follows the extinction of dinosaurs. This work, published in Biology Letters, challenges the long-standing hypothesis that competition decided the fate of ancient top predators.
Our cats, dogs, bears, and walruses, and their ancestors – forming together the clade Carnivoramorpha – once shared the planet with other groups of large meat-eating mammals that have since vanished. These groups, chiefly among them hyaenodonts, evolved large body size early in the Paleogene and became the top predators of their ecosystems. They disappeared in a step-wise fashion tens of million years afterwards, while carnivoramorphans diversified into a myriad of shapes, sizes, and ecologies.
The long-standing theory explaining this shift held that carnivoramorphans won their place at the top of the food chain by outcompeting the other clades, thanks to their more versatile teeth; but this idea rests almost entirely on the North American fossil record. To test this, the team investigated the rich fossil record of Europe and focused its efforts on reconstructing body mass trends from that record.
“Body mass is a powerful clue of the ecological role of continental animals” explains Prof. Valentin Fischer, director of the Evolution & Diversity Dynamics Lab at the Université of Liège and co-lead author of the study. “Because of these strong bonds between ecology and body mass, it is actually possible to reliably infer the body mass of ancient predators by measuring key traits in their dentition.”
Armed with body mass data on 155 fossil species spanning nearly the entire Palaeogene period, the scientists found that carnivoramorphans grew larger and far more diverse in body mass shortly after an abrupt global warming event 40 million years ago, known as the Middle Eocene Climatic Optimum. Contrary to what is seen in North America, their supposed rivals showed no associated decline; European hyaenodonts remained diverse for millions of years afterward, only declining following a major cooling event around 34 million years ago known as the “Grande Coupure”.
By showing that Europe's carnivoramorphans and their rivals coexisted for a long time, and that body-size change tracks climate events rather than diversity, this study suggests that regional climate, not a universal competitive advantage, decided who ruled as top predator, with strong differences in tempo across continents. The lineages that gave rise to todays’s lions, wolves, grizzlies, and racoons were shaped by past climate changes, and are now threatened by it.
Journal
Biology Letters
Method of Research
Meta-analysis
Subject of Research
Not applicable
Article Title
The rise of carnivoran mammals in Europe through the lens of body mass
Article Publication Date
15-Aug-2026
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