Evolution of sabre-toothed predators’ deadly teeth

The predators through time

Sabre-toothed predators once roamed ecosystems around the globe. Their fossils have been found in North America, Europe, Africa and Asia. The feature that defines them are their sabres, a distinct type of canine tooth. These teeth are long, sharp, laterally compressed (flattened from the sides) and curved.

This is different to the short, robust, conical canines of modern big cats such as lions and tigers. This iconic tooth is older than the dinosaurs. It first appeared around 265 million years ago in a group of mammal-like reptiles called the gorgonopsids.

Evolved repeatedly

Over millions of years, sabre teeth evolved repeatedly in different groups of carnivorous mammals, marsupial relatives like Thylacosmilus and 'false' sabre-tooth cats such as Barborofelis. The most well-known sabre-toothed predator is Smilodon. It persisted until just 10,000 years ago.

Based on extensive research into sabre-tooth ecology there is a general consensus that these predators primarily targeted large prey, delivering slashing bites to the soft tissue of the throat powered by strong neck muscles. It is thought that their teeth offered an advantage doing this, helping them to deliver the killing bite.

Testing the puncture-strength trade-off

Specifically, the researchers tested if their shape was an optimal balance between two competing needs related to tooth function. First, being sharp and slender enough to puncture prey effectively. Second, being strong and robust enough to resist breaking. To investigate this, they conducted a large-scale analysis of more than 200 different carnivore teeth, including both extinct sabre-toothed species and modern animals.

First, they measured their 3D shape to show how sabre teeth compared to other carnivores. Then it was tested how a subset of these teeth performed during biting via two experiments. Experts 3D printed tooth models in stainless steel and drove them into a gelatine block (simulating prey flesh) to measure how much force was needed to puncture. They used metal replicas to prevent tooth bending during the experiment, ensuring accurate puncture force measurements. They also ran engineering simulations to test how much stress different tooth shapes experienced under biting forces. This revealed their likelihood of breaking. Finally, they conducted an "optimality" test to determine which tooth shapes struck the best balance between puncture efficiency and strength.

Extreme to less extreme forms

In terms of sabre-tooth shape, the results challenge the traditional idea that these predators fell into just two categories: dirk-toothed, which are long and slender, and scimitar-toothed, which are short and laterally compressed. Instead, they uncovered a continuum of sabre-tooth shapes.

Prone to breakage

This ranged from extreme forms, such as the long, curved canines of Barbourofelis, Smilodon and Hopolophoneus, to less extreme forms, such as the straighter, more robust teeth of Dinofelis and Nimravus. The results reveal that the extreme sabre-toothed forms, like Smilodon, were optimised for puncturing prey with minimal force. However, they were more prone to breakage under high stress. Less extreme sabre-toothed forms, such as Dinofelis, were also optimal but in a different way. They struck a more balanced trade-off between puncture efficiency and strength. The fact that different sabre-toothed species evolved varying balances between puncture efficiency and strength suggests a broader range of hunting strategies than previously thought. This supports a growing body of research on their ecological diversity.

A striking solution

These results help explain why extreme sabre teeth evolved so many times, likely driven by natural selection for an optimal design. They also provide a possible explanation for their eventual demise. Their increasing specialisation may have acted as an "evolutionary ratchet", making them highly effective hunters, but also more vulnerable to extinction when ecosystems changed, and their prey became scarce. The study also provides broader insights into how extreme adaptations evolve in other species. By integrating biomechanics with evolutionary theory, one can better understand how natural selection shapes organisms to perform specialised tasks.

Sharpness and durability

The sabre tooth form represents a striking solution to a fundamental mechanical challenge, balancing efficiency with strength — one that is also reflected in human-made tools. This trade-off between sharpness and durability is a key consideration in engineering, influencing the design of everything from surgical scalpels to industrial cutting blades. Engineers developing precision tools, such as hypodermic needles or high-performance cutting instruments, can look to nature's evolutionary solutions for inspiration, applying the same principles that shaped these prehistoric predators. The Conversation