Whales are the largest animals of our planet. The adult blue whale is approximately 25 meters long but might be up to 33 m and weighs up to 200 tons. The heart of these animals is the size of a small car. Scientists have long been looking for an answer to why whales have grown so huge during the evolution.
There are a few answers: some researchers believe that whales adapt so well to their habitat, some point to intra-species competition or resistance to predators; some refer the rule of Cope that representatives of any kind grow bigger over time without any particular reason. Which of these theories is closest to the truth? And when did whales start growing so big?
The story of whale evolution is very interesting. All whales (whales, dolphins, and sea pigs) are the offspring of terrestrial ungulates, that are some distant relatives of deer, giraffes, and cows. The nearest current whale tribe is the hippopotamus. Whales are thought to have migrated from land to oceans about 50 million years ago, after an extinction of an empty and harmless niche in the water after the plesiosaurs died out. Initially, the ancestors of whales lived near water bodies and hunted fish, then spent more and more of their lives in water until they finally fully adapted to living in the water. Their limbs became fins, the shape of their tail changed, and their nose holes moved to the top of their heads and became vents. However, the whales still are warm-blooded mammals, and they are breathing with the help of the lungs.
The ancestors of whales were the size of cats and dogs. Why did some whales become so huge? When did this happen? Macroevolutionary biologists are looking for answers to these questions. They studied the remains of both modern and fossil whale fossils and, based on the information obtained, formed a genealogical tree showing the relationship between whales and their oldest ancestors.
Biologists have come to unexpected conclusions. This is the first study to explain how, when, and why humpback whales grew to current scales. Scientists believe that although whale whales appeared about 35 million years ago, their gigantism manifested itself much later 2-3 million years ago.
However, the process began a little earlier, about 4 million years ago. Until then, the maximum length of humpback whales living in the oceans did not exceed 10 meters. This is important: the process of growth of different members of the subspecies of whale whales took place in parallel, that is, the different branches of whales did not have a common giant ancestor, but began to grow independently of each other. Why whales were medium sized during 90% of the time of their evolution and then suddenly increased? It has previously been speculated that whales may have grown so in defense of large predators or because a larger body may have a thicker subcutaneous layer. This is an important factor in survival in cold water. A popular version is that large animals feed by filtering water and thus obtaining energy more efficiently and using it optimally during migration. However, a new study suggests that none of these causes could have led to a sudden increase in the size of animals in a particular epoch