Evolution is an ongoing process for the time life started on planet earth. In different time zones, the environmental conditions were different and hence it supported various life forms. There are numerous pieces of evidence that show evolution is for real. This evidence is further supported by the new addition with time. This article is going to find out the facts that lie behind evolution.
Claims about evolution:
There are two popular claims about evolution, explained by Charles Darwin in his book “Origin of species”
- All living organisms evolved from a common ancestor.
- The evolution is powered by the natural process.
Living organisms are related:
It is not possible to study every organism related to a common ancestor. We will take the example of Cetaceans of the world. This branch includes Whales or Dolphins. Scientists believe that the whole group is related and evolved from the land mammals. There are several similarities that we are describing below.
Comparative anatomy of whales:
Whales are very much similar to land mammals.
Placenta:
They have placenta to give birth to their child as well as they feed them milk.
Gills:
Unlike fishes, they do not have gills rather they respire with the fully developed lungs just like humans.
Blowholes:
They have a blowhole on the top of the body which looks like nostrils in men. Inside the skull, both nostrils have nasal passage. These blowholes can be a highly modified mammal’s nose.
Hairs and bones:
Whales actually have hairs on their body just like land mammals. Also, there are arms, hands, and finger bones inside their flippers. The same bones are present in bats, hippos and humans have in their front appendages. These bones are the wrist, hand, finger bones, Ulna, radius, and Humerus bones.
Backbones:
Whales do not have similar bones forming hind limbs. But there are some unique bones that are similar to the limb. There are unique pairs of bones that look like hips, thighs, and chin bones. In fact, it also has a ball and socket joint just like you have in your own hips. It may be a coincidence or are these organisms are really related.
Embryology and development:
Embryology is the branch of biology that shows how organisms before becoming a fully developed fetus. There are also many similarities between land mammals and whales during embryonic development.
Buds in embryo: The dolphin and human embryo look similar. There is arm and leg bud which is alike. In humans, this leg bud will develop into a leg but in whales, it will grow for a certain time and then fade away. However, the rest of the embryo continues to grow.
Nostrils:
During embryonic development, there are two nostrils grooves in the dolphin. As the fetus grows, these nostrils migrate on the top of the body forming blowholes. These blowholes are very much similar to land mammals.
Fossil records:
The fossil record also supports evolution.
Basilosaurid whales fossil record:
This fossil record was collected around 34 to 40 million years ago. It was directly collected from the land.
Basilosaurid skull:
The basilosaurid skull of Dorudon atrox shows a similar model. In the skull, there is no nasal opening at the top of the head just similar to the modern whales. Also, it is not at the end of the skull as we see in buffaloes, goats, or any other land mammals. Rather it is present in between both of the passages. It shows that Basilisaurid was an intermediate species which confirms the evolution.
Basilosaurid hind limb:
At the back of the fully developed body, there are hips, legs, ankles, feet, and toe bones. Obviously, these bones are small enough for supporting a walk on land. But it may have been used for several other purposes such as scratching parasites and itchy skin of their own.
Maicetus Inuus fossils record:
The Maicetus fossil record was collected almost 47.5 million years ago. The scientists believe that the more we go in back times the more it becomes difficult for the whales to distinguish them from land mammals. The hip bones of the Miacetus are considered strong enough to walk on land but there are many reasons to call it whales rather than categorizing it as a land mammal. The skeleton is similar to the sea creature. The leg bones are small bones that combined with the flattened toe bones showing that they were swimmers with their legs and feet.
Maicetus skull:
The skull structure is very similar to the whales and land mammals. The jawbones are similar to the basilosaurid whale. There is a unique structure of the ear bones that match with the land mammals. It appears like a walking whale. Scientists have found many other fossil records that show their similar relation with the four-legged land mammals and whales. This shows that the whales are also evolved from land creatures.
DNA comparison:
DNA is the unit of heredity. It is just like a recipe for the development of the organism. There are several chemical markers in it. So without looking at the bones and other body structures, scientists can predict the evolution by comparing different DNAs. The whale DNA has been matched with organisms such as fishes, humans, sea lions, etc. However, the closest genetic match is with the water-loving hippos. It is not true to say that whales have been evolved from hippos but there was a common ancestor of both organisms that had lived in the past about 54 million years ago.
Mode of feeding:
The unique similarities between whales and hippos had made scientists as surprised. The whales are carnivores that feed on small crustaceans and fishes. On the other hand, hippos feed on plants. But still, they share many common features that may have come from their common ancestor.
Ankle bones:
The ancient walking whales had ankle bones which are only found in hippos or their close relatives.
Giving birth:
They both of them give birth and feed their children with milk.
Stomach:
The multi-chamber stomach of both hippos and whales are similar in physiology.
Final verdict:
We are wrapping the whole discussion into a single phrase whale has been evolved from four-legged mammals. There are many several disciplines that support the notion via pieces of evidence. It is not only about whales that they are similar to land mammals. There are many other organisms having similar structures as we see in the terrestrial organism. For example, we know from embryology, fossils, DNAs, and many other disciplines showing that land the bird wings are very much similar to the modified arms and the claws.
They may have evolved from ancestors like dinosaurs. The wings of the bats are evolved from the five-fingered mammals which are very similar to the monkeys, humans, chimpanzees, etc. The common ancestor of humans is chimpanzees. The mammals evolved from reptile-like creatures and then it was evolved from amphibians. Amphibians evolved from fishes and fishes share a common ancestor with the segmented worms. There are thousands of the evidence from an independent field of the study shows come to a final verdict that all living organisms are evolved from a common ancestor.
