A Jew who adheres to kosher can eat only selected animals. That was achievable in the primitive economies that Jews lived in when these laws were handed down and certainly remains feasible today in a world of mass production and transportation.
But let's say that a time traveler goes so far back in time that modern kosher animals, such as the sheep, haven't evolved yet? Can a faithful Jew eat a dinosaur? Which kind of dinosaurs are acceptable and which are prohibited?
Roy E. Plotnick, Jessica M. Theodor, and Thomas R. Holtz answered these questions in a recent article in the scholarly journal Evolution: Education and Outreach:
The determination of whether an ancient mammal had cloven hooves can be done directly using fossils of the limbs, by inspecting the foot symmetry, to make sure it passes between toes 3 and 4, and the shape of the last phalanx of the toes, which should be wide and flat, not pointed or curved (Figs. 3, 4).
Determining whether an animal chewed the cud is much more challenging. Because teeth are what are used to chew and they are by far the most common mammalian remains, they would be the logical place to determine from fossils whether or not an animal chewed the cud. Unfortunately, there are no discernable differences between the teeth of cud-chewers and non-cud chewing artiodactyls. First, one might think that regurgitating so much material back into the mouth might bring excess stomach acid into the mouth and cause recognizable damage to the teeth; however, part of the evolution of rumination (cud-chewing and multi-chambered stomachs) included a system of acid reducing mechanisms. The chewed and digested plant matter is regurgitated into the mouth, where the saliva has a high concentration of bicarbonate, which acts as a buffer to the stomach acid coming into the mouth with the cud (McDougall ). This reduces the incidence of acid wear on the teeth.
You can read a summary of the authors' kosher paleontology at Real Clear Science.
-via Jonah Goldberg