The theories of evolution involving the manatee are very interesting. The oldest fossils that have been found date more than 45 million years ago. Even though they have been extensively studied, there are still plenty of questions that remain. The links though of those fossil remains have plenty of missing pieces and that is where theory comes into the picture. Being able to identify the ancestors of the manatee has proven to be very difficult.
The oldest of these fossil remains where located around Jamaica. This has led experts to believe that during that time they came from Africa and Eurasis. They may have reached the area of South America around the Middle Eocene Period. This would be 45 million to 50 million years ago.
Some of the studies conducted have involved a biochemical analysis of the proteins. This has allowed the fossils of manatee to be compared to elephants, small mammals, and aardvarks to see how well they would relate genetically. However, what the results show is that the manatee could be related to hooved animals. They share the small characteristic of not having a collar bone. They also feature nails rather than claws.
Based on that information, one theory that was popular for a very long time is that the manatee was closely related to the walrus. With the advances in technology and various studies though this theory was eventually proven to be incorrect. Based on the information that has been credible with the fossils, the early manatees were about the size of pigs. They also had four legs and they lived both in the water and on land. They also had a very powerful tail.
Some of the evolution changes then that would have occurred over this time is the disappearance of the legs and them becoming completely aquatic. The back appendages aren’t visible today, but they are internal around the pelvis region. Another significant change would be that of the tail which is now paddle like and used to help them successfully be able to navigate around in the water.
Along with the changes to their bodies for living in the water, they likely had changes to their diet too. It is possible that the early manatees and ancestors actually consumed meat as well as vegetation on land. Changes to the overall design of their teeth is also interesting to look at. Once they were herbivores, they didn’t need sharp teeth but only flat ones to help them grind up the food prior to swallowing it. The ability to replace teeth as needed is also believed to be part of their evolution.
Today, the manatee is referred to as the sea cow. They are the only marine mammals that are herbivores and that are completely aquatic. This means that they don’t come to land at all. There are some theories that indicate a diversity between Miocene and Oligocene and that could have occurred as a result of the temperature cooling, changes in the oceans, and even human factors. It is believed that there was once at least several more species of manatee but they are extinct.
There are still quite a few theories out there about the manatee, and as research continues some of it is deemed to be accurate and other information is eliminated from the equation. It takes lots of testing and time to give credibility or to rule out something along the way. It can be very interesting though to explore the possibilities and to look at the remaining theories. Perhaps you have your own beliefs and ideas about the evolution process of the manatee from millions of years ago to what we know of them today.