Facts and Information
The concept of evolution for any living creatures is one with theories and debates. When it comes to sharks, that is no exception. However, there have been fossilized remains found of them that help to provide us with some necessary evidence. Most of what has been found is shark teeth. Due to the amount of teeth that they have, this is of great value when it comes to such research.
They date back to the Ordovician period which is about 420 million years ago! The fact that these creatures were around that long ago is very fascinating! Some of the species haven’t’ changes much at all. Overall though there have been some remarkable things identified that indicate evolution has been involved in their survival.
Where the biggest debates come into the picture though has to do with the fact that scales only have been found and some Paleontologists aren’t convinced they are from real sharks. If they are though then that means these early sharks looked significantly different from what we see today. That would mean a great deal of evolution took place over time to ensure they were able to survive rather than face extinction.
The biggest collection of early shark fossils are dated to 370 million years ago. They were found in the USA along the states of Tennessee, Ohio, and Kentucky. It is believed that the rocks here formed from the sediment of the shallow ocean that was at that time around a big portion of North America. One of the main differences from today’s sharks has to do with the teeth. They were worn down on the fossils.
This indicates to the experts that the replacement of shark teeth for the duration of their life was an evolutionary factor. A theory is that many sharks in those early times weren’t able to survive once their teeth began to wear down. The evolution here could have allowed the sharks to have a longer life span. This could indicate that numbers were low and that they needed a way to live longer?
The fact that sharks don’t mate until they are at least 10 years of age could have been a part of that evolution. If sharks weren’t able to survive due to teeth problems then it would have threatened their overall survival. The fact that they only give birth to one pup most of the time could be evolution too. Many fish have large numbers of young with high mortality rates. Lower birth rates can help sharks to offer more protection to the young.
Another significant difference has to do with the size and shape of the fins. The theory is that these early sharks were more agile and faster than what we see today. Perhaps evolution slowed them down though to help reduce the amount of food they would have to consume to survive and to allow them to conserve energy.
Today, few species of sharks are able to survive in freshwater. However, there are fossils that date back anywhere from 150 million to 300 million years that indicate that many of them were able to live in freshwater. What occurred though that resulted in evolution so that they would only survive in saltwater is still a great mystery to scientists today.
Even though we don’t have all of the answers yet about what occurred with shark evolution, we do have plenty of pieces to that puzzle. There continues to be theories in place that are tested and with new technology even more are sure to emerge! Many experts believe that the skeletal remains of early sharps are buried deep in the sand at the bottom of bodies of water. Perhaps one day we will have the tools and technology to reach them successfully.