Many kinds of methods used to protect humans from sharks are increasing the decline of the shark species. Many of these methods cause more harm to the shark and their species. So how long have Sharks been on Earth for?
Fossil evidence shows that sharks populated the planet before the dinosaurs existed, more than 400 million years ago. Since the skeleton of the shark is composed primarily of cartilage, the only thing conserved from prehistoric sharks are fossil samples of the dermal denticles and teeth, but there are some exceptional cases of preserved skeletons.
Certainly, not all of the sharks that once were on Earth exist today. Fossils prove that many species have become extinct.
Some of the early forms of sharks were rather small. There is indication to suggest they looked more like fish. Some others were similar to eels; their faces featured noses that were round rather than pointed. Some others were huge with extraordinary dimensions, much larger than the largest shark available today.
Sharks did not have a brain as large as they have today. More than 2/3 of the size of their brain is for the senses, and this is one of the areas where sharks have significantly been able to evolve and to become a more intelligent species.
Their teeth were also different than they are today. Instead of being razor sharp they were smooth. However, these early descendants also had the rows of teeth that replaced the missing ones like they do today. This kind of teeth could indicate that prehistoric sharks fed on plants instead of being meat eaters as some are today.
HOW EXACTLY DID SHARKS EVOLVE OVER TIME?
Darwin’s Theory of Evolution is a slow gradual process. Darwin wrote, “…Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps.”
“Natural selection acts to preserve and accumulate minor advantageous genetic mutations. Suppose a member of a species developed a functional advantage (it grew wings and learned to fly). Its offspring would inherit that advantage and pass it on to their offspring. The inferior (disadvantaged) members of the same species would gradually die out, leaving only the superior (advantaged) members of the species. Natural selection is the preservation of a functional advantage that enables a species to compete better in the wild. Natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes in domestic animal populations by selecting individuals to breed. Breeders eliminate undesirable traits gradually over time. Similarly, natural selection eliminates inferior species gradually over time.”
So alternatively some sharks were born with features that made them better able to survive. A shark with a useful feature would pass along that feature to its off spring. Over millions of years, this happened from generation to generation. Sharks with superior features would reproduce rapidly and sharks without those features died off because they could not compete successfully for food and mates.
The rate at which sharks are killed by methods used to protect humans from sharks, or the rate at which sharks are killed by the fishing industry for the consumption of humans. Sharks are unable to reproduce at the same rate. The reproduction process of a shark takes year before reaching maturity. And many of their young are endangered as they are sources of food for other marine life.
Having survived years of evolution, dramatic changes in seasons and other predators, the odds are not in their favour. Excessive consumption, ignorance and little understanding will see them fade into fossil evidence that we will look at years from now.
WRITTEN BY: LANA SAMUELS