Evolution of Dolphins
When it comes to evolution, it is very fascinating, and collecting the data to back up the theories can be time consuming. What has been noted about evolution is that there are signs of it with just about every living thing in the world. It is believed to be a slow process that allows survival of the fittest to occur. Due to changes in environmental factors, the physical anatomy may need to change in order to be as effective as possible.
The process of evolution has been identified in dolphins and it is believed they are connected to many terrestrial mammals. This is based on research that shows them to be part of the Artiodactyl order. What has been identified are ancestors of the dolphins that date back more than 50 million years. Before you say that there is no way that dolphins are related to land mammals, you have to look closely at the facts.
There have been plenty of bones found that allow researchers to look at the development of the fins and overall anatomy of the dolphins. What has been found is that the limbs are like those of land creatures. For example, fish have spines that move horizontally but not dolphins. Instead, they move vertically which is the same as animals that live on land. The fact that dolphins have to go to the surface of the water to get air is also a factor to take a close look at.
Based on the findings of bones, the skull of dolphins have been looked at. They have changes both to the size and the shape of them. They have become larger and that would be due to the fat that developed in the melon and the lower jaw. The extension of it to the middle ear for hearing and for echolocation is a prime example of how the body of these dolphins changed over time to help them survive in their environment.
The information found indicates that during the early Miocene Period, the use of echolocation formed. It has proven to be one of the means for survival that the dolphins rely heavily upon today. Based on the fossil findings, early dolphins were very small but they still consumed fish as their primary diet. They may have eaten other small organisms though as well.
One significant theory is that the evolution of whales is the result of them developing from hoofed land animals. When you look at the teeth of a whale that are triangular, they do match those of wolves and toed ungulates. However, new information over time has moved away from such a theory. What is now believed is that the ancestors of the whales are more likely to be the hippopotamus. The argument against this though is that the hippo wasn’t found in the fossil records until about 1 million years after the Pakicetus, which is one of the first known ancestors of the whale.
Such information does tell us that whales aren’t related to Mesonychids as once thought. They are actually Artiodactyls that split from the Mesonychids and that is likely when they began living in the water versus living on land. They continued to be carnivorous in the water though instead of becoming herbivores like so many other mammals.
The outward part of the whale in regards to the hind area is smaller now and more internalized than in the past. There have been times though when small legs can develop called atavism. This could be the result of genetic coding that will cause other longer extremities to be developed. Another part of evolution that has been identified is that the nasal openings moved to the top of the skull. They were once at the end of the snout, and this change is referenced as nasal drift.
From there, the nostrils developed through evolution into a blowhole so that they would be able to go to the surface of the water for air and then submerge again. Another noted movement was the ears closer to the eyes. Such changes helped them to be able to survive in a new environment in the water and further moved them genetically from their ancestors that would remain land mammals.
Identifying what has occurred through evolution over the span of millions of years is never easy. However, as new evidence comes along to be found and new technology is applied, answers can be found. It can be fascinating to look at the various theories that are in place and what has been proven or disproven from them. There are some changes right now that could indicate evolution at work for dolphins.
This is in regards to some embryos being noted with hind limb buds that are at the base of the fluke. They are only about 1 inch long but they are new in terms of the overall anatomy of the dolphins. The current body of a dolphin involves two small pelvic bones, rod shaped that are internalized. In 2006 there was a Bottlenose Dolphin found in Japan that has these external fins on the body.
