Understanding Evolution: Vestigial Structures

Humans are curious creatures and finding out where they come from is one way to satisfy their curiosity. This leads to the discovery of a logical reason known as evolution. Evolution gives answers to how we advance as humans by evidence provided from fossils and DNA. In the year 1859, Mr. Charles Darwin wrote a book called “Origin of Species", which had been the pioneer of a theory that has become fact. It had been rectified over the years so now it is a very reliable historical fact that is being supported by evidence stored in the earth and interestingly enough in our bodies. We can now see that everything shares one ancestor. And I stand by the statement that we evolved from a common ancestor.

Evolution is a theory turn fact that had its merits processed over and over again. A broad heading called scientific theory tested the theory back then. A theory is a statement that is not supported by evidence. In science, we refer to it as a hypothesis. Mr. Darwin came up with a hypothesis which he later released in the above-mentioned book. It revealed observations that had no evidence. In later years, several scientists came across these notes and started acquiring evidence to support the hypothesis. These notes stood out because of the remarkable amount of overlooked observations. What makes this important was that the explanation was simple and when compared to what was already known the chances of it being true were great. The law of parsimony states that the fewer assumption decides on an observation can be the correct way to explain that hypothesis. When these pieces of evidence came to the forefront, a group of scientists with knowledge critique it. This is a peer review because they highlight flaws and give their honest opinion on the subject matter. When evolution was being praised the number of criticism caused other scientists to look for evidence to support it. Now evolution is a fact taught in schools because when tested it was established as the truth. It is important to note that evolution is a new term to describe this process. Darwin explained evolution using the phrase ‘descent with modification’ through a process called natural selection. This means that certain features of an animal will look different in their offspring over time. It is a gradual process thus; these animals need to reproduce. To reproduce, they must be of age to mate, give birth and nurture the young. When an organism is healthy, it has a good gene or good traits. These genes are often seen in the young because it is one that one or both parents have. Nature wants every organism to be at its best potential. So, when a bad gene or trait is present in the genetic pool, it tries its best to get rid of it. It does this by the killing of the organism before it can reproduce. This is natural selection.

Natural selection does not mean that all the previous organisms must die. Environment plays a role in this. Animals in different environment develop trait to survive in that environment through adaptation. An example of this is bears. Polar bears have white fur to camouflage them from predators and hunters. Other bears have black or brown fur. Research shows that polar bears have black skin but the fur is hollow making it look white. That shows that polar bear had to adapt to the environment to survive. If they had dark fur in an all-white environment, they would have all died because they were being hunted. So for them to survive in this environment, a good trait to have was hollowed fur. This means when bears with black fur entered the Arctic region, one of them suddenly had a mutation that made the fur hollow. This mutation became favorable to that environment and when that bear reproduced its offspring had hallowed fur. This continued until polar bears i.e. the new species of bear emerged. This good trait is now passed onto the young ones. And this is how a new species came about from natural selection.

However some parts of our structure are still like our ancestors. In fact, all animals share what we call homologous structures. Goats, horses, humans and whales all have this large bone called the humerus. This humerus is attached to 2 bones; radius and ulna and then branch out to form fingers. Horses have bones known as the hooves. Under further inspection, we realized the two bones fused together. This structure found in animals dated all the way back to the Tiktaalik. Tiktaalik is a transition fossil found that had a sturdy wrist bone and 4 limbs webbed fins. This fossil showed a transition from fish to reptile due to its fish-like body but the flat head with eyes on top. Now this bone found in the Tiktaalik was not found in fishes but in every other animal thereafter. These evidence points towards a common ancestor. it also shows that rhinoceros have come a long way from its ancestor. Rhinoceros came from the perissodactyls. It is not known where the perissodactyls evolved. They are the common ancestor for a range of animals; horses, tapirs and rhinoceros. Perissodactyls were herbivores that walked on an odd number of toes. They were the large group of mammals present in the Miocene era.

Due to global cooling, several of these animals went extinct and only the tapirs, rhinos and horses remain along with some distant groups. Because of their diet, tusk-like incisors at the top and chisel-like incisor at the bottom developed. Due to migration, these animals moved to various parts of the world. Many rhinos then lacked nasal horn but when these evolved they were side by side. Today they are grown back and front. The menoceras, small rhino fossils found in North America is proof of this. This also showed that only male rhino had these horns. Also, these rhinos showed sign of the incisors. Teleoceras rhinos had short limbs, long torso and short nasal horn. These rhinos were female and they went extinct. Fossil records showed that the males of this species died at a younger age because of wounds from horn and tusk. It is believed these were because of fights for the female counterpart. Painting on cave walls showed rhinos with long fur coats. Fossil records showed that they had broad, flattened horn. It is believed that they use it to push away snow to get to the vegetation underneath the snow. These animals have all branched out and evolved in some way. Due to their toes, teeth and structure, they have a common ancestor. Notably, some organisms have structure or organ within themselves that belonged to their ancestors. The role of these organs in our body may have diminished, change or have altogether lost its function. These are vestigial structures because their original function is no longer used. A common example is that of the appendix in giraffes and also humans. It is no longer needed to break down complex cellulose in our diet like for our common ancestors. We can survive without it. Another example is that of cave-dwelling tetra fish. They have eyes on their heads that does not work because they are blind. And an even stronger example is that of tailbones in humans. Our ancestor had tails but we don’t. Our tailbone however is use to give support will sitting. These structures are important because it shows that we have a common ancestor and as we evolve from them some things still remain.