Sharks: Delegitimizing the Myth about the Absence of Evolution
One can hardly deny that today, people mostly learn about evolution, extinct animals, and living species via mass media. Indeed, from the very childhood one is surrounded by dinosaurs, mammoths, giant cave bears, and other astonishing creatures once walked the Earth. Being spectacular and looking unusually, these animals highlight the actors on background, which are the most interesting one – sharks. One quickly gets amazed by the myth claiming that million years ago, when the continents had a different shape, and giant reptiles inhabited the land, sharks that we know today were almost the same, just had some bigger size and mass. However, there is hardly a species that omitted the impact of the everlasting evolutionary process, so one may doubt that sharks are an exception to the universal rule. The comparison of fossil and extant sharks proves that sharks have significant anatomic differences between the past and current species, and between the species living now, which refutes the hypothesis that the sharks have not experienced revolution, creating a need to revisit a popular image of this fish.
Sharks of the Past
The sharks have a long history and a specific body structure, which differentiate them from the extinct and living fishes. According to Klimley, the first fossil record of shark skeletons date back to 455 million years BC, and their role in ecosystems varied (12). It is assumed that all of the prehistoric sharks were predators, but later, some of them began eating plankton and algae, while others learned to suck out backboneless animals from the silt of the sea floor. Just like modern sharks, they had five gill intakes on the both sides of their bodies, as well as the similar position of fins and other navigational parts of the body (Klimley 18). In the Jurassic period, streamline and flat-shaped species had subdivided, and it is the earliest time when sharks and their relatives rays could be tracked separately.
Both modern and past sharks have a number of features which increased their survivability. First of all, it was the particular structure of teeth, which differentiated sharks from any other cartilage fish and other animals (Nyberg et al. 806). Sharks have always had multiple rows of teeth in their mouth, which substituted each other to prevent functional damage, deterioration, and guarantee sharpness (Klimley 12). Thus, these predators had always had a possibility to kill and eat their prey regardless of hardness they suffered. From the scientific point of view, the abundance of teeth presented researchers the opportunity to study the behavior, lifestyle, and life duration of sharks of the past (Long and Waggoner 37). Unlike the remnants of the skeleton, one may easily find shark teeth in mines, barrow pits, and on sandy beaches, anywhere where a human and nature erode the sedimentary rock.
Another peculiarity of all sharks is that their offspring grows inside their body. Unlike other species of fish, they do not lay eggs, …