Dental Tradeoffs Drove Mammalian Carnivore Evolution

Mammalian carnivores look incredibly diverse, yet their evolution appears to rely on a surprisingly small set of dental solutions. A new study reports that a built-in performance tradeoff—between slicing flesh and crushing hard materials—repeatedly constrained how predator teeth changed over time. Because carnassial teeth are both durable and closely tied to feeding habits, they provide a powerful window into mammal ecology and evolutionary history.

In mammals, heterodont dentition allows different tooth types to specialize for distinct tasks. One key innovation is the tribosphenic molar, whose geometry can support both cutting and crushing in a single bite. But that flexibility comes at a cost: improving one function tends to reduce the other. Until now, it has been unclear how evolutionary pressures balanced these competing demands across the wide range of carnivorous diets seen in nature.

To explore this, Narimane Chatar and colleagues analyzed three-dimensional lower carnassial tooth shape in 250 living and extinct carnivorous mammals. Using geometric characterization of tooth morphology, they identified two recurring designs. One features a highly specialized, blade-like tooth with a reduced grinding surface, matching obligate meat-eaters such as cats. The other enlarges the grinding region, enabling a more omnivorous lifestyle typical of animals like dogs and bears.

The patterns suggest that modest developmental shifts can generate substantial functional differences while remaining limited by genetic and anatomical constraints. In other words, tooth evolution may repeatedly “snap” toward a small number of workable performance landscapes rather than exploring every possible shape.

The team tested the functional consequences by producing 3D-printed carnassial models and evaluating their performance under conditions designed to measure cutting versus crushing. Results revealed a sharp tradeoff: very few species—less than 1%—came close to being optimal at both functions simultaneously.

Most species instead showed a clear division of labor. Teeth optimized for slicing tended to perform poorly when asked to crush hard materials, while crushing-adapted teeth sacrificed cutting efficiency. For hypercarnivores, the blade-like carnassials closely matched theoretical shapes predicted to maximize cutting effectiveness, implying that natural selection repeatedly favored efficient designs even across different evolutionary lineages.

These findings frame mammalian predator evolution as a constrained optimization problem. Rather than unlimited redesign, carnivores appear to evolve along two dominant dental routes shaped by physics, development, and selection—explaining how different diets could repeatedly emerge from the same underlying dental toolkit.