Everyone loves a good depiction of prehistoric feasting--whether that's a dire wolf chowing down on a prehistoric bison, or a Stegosaurus
grazing on some ferns. So, how do we know what prehistoric animals ate?
Allosaurus dines on a dinosaur carcass--this reconstruction by Charles Knight was based on sauropod bones that showed tooth marks from feeding!
Many different lines of evidence helps paleontologist reconstruct prehistoric diet--let's take a look!
- Anatomy. Most modern carnivorous animals have sharp teeth to slice up meat, and we can extend this observation back through time to infer diet in fossil critters. Even plant eaters with different diets have different teeth and jaws. For instance, an animal that primarily eats grass will have a different anatomy from one that primarily eats tender leaves.
- Engineering. Through evolution, skeletons are adapted to different functions. Levers are a basic principle of physics and engineering, and an understanding of them can help us figure out how long-gone animals moved and chewed. For instance, the placement of muscle attachments on jaw bones directly impacts the amount of force that is applied at the teeth and how quickly the jaws can close. The robustness of the skull also can relate to its overall strength, and a really beefy skull might indicate a diet favoring really tough food--we can do more in-depth comparisons using engineering modeling software. An understanding of concepts such as levers, force production, and bone strength helps scientists reconstruct diet and chewing patterns.
- Chemistry. You are what you eat, and this applies even at the molecular level. Different food sources have different trace elements and isotopes in them, and these are in turn absorbed into the teeth and bones of animals in the next step up the food chain. Chemical analysis has pinned down what plants prehistoric horses ate, or whether an ancient scavenger was feasting mainly on marine or terrestrial animals.
- Guts. Sometimes, the remains of an organism's last meal are fossilized in its belly. That can be a dead-obvious (no pun intended) indicator of diet.
- Poo. Coprolites, or fossil feces, often preserve digestive leavings such as plant fragments or bone bits. If you can match the poo with the organism that made it, it's a great window into diet (as well as the animal's digestive capabilities).
- Tooth marks. As shown in the picture at the top of this post, feeding leaves traces on bones. Although it won't necessarily tell you that one organism stalked and hunted another, these marks can tell you at least that one organism ate another.
- Tooth wear. Even under the best of circumstances and with the softest of diets, food marks up your teeth. Different diets can be tied to different patterns of pits and scratches.
Many of these lines of evidence require a solid understanding of modern animals--so, paleontologists have to spend a lot of time looking at today's critters. Even then, it's important to be cautious--for instance, different diets may leave very similar scratches on the tooth surface, and we probably shouldn't compare an ancient dinosaur's teeth too closely with those of a modern horse. Multiple lines of evidence are important!
Why should we care what some animal ate 20, 120, or 200 million years ago? First--it's amazing that we can know something that detailed about the life of a long-dead animal! Second, our quest to understand prehistoric animals highlights how much we don't know about today's organisms--and spur us to answer the kinds of questions that might have additional applications in veterinary medicine, conservation, and biology. Finally, that ancient animal's diet is part of our planet's story. As we track changes in diet, we can better understand the evolution of life on earth, how it responded to changes in habitat and global environment, and how today's life might respond to current and future changes. The past matters!
--Dr. Andy Farke is the Augustyn Family Curator at the Raymond M. Alf Museum of Paleontology in Claremont, California.