Physiological Changes in Dolphins

Dolphins have been a great source of fascination ever since the discovery of their existence. An abundance of myths and mysteries surround this marine mammal, and many note the distinct similarities in intelligence to that of humans. Modern science has since debunked much of the folklore associated with this mammal, but recent studies have produced intriguing revelations concerning their physiology, evolution and acquisition of their intelligence.

  1. Species

    • Dolphins are cetaceans, or members of the order Cetacea. They belong to the sub-group of "toothed" whales called Odontoceti. This group makes up the vast majority of cetaceans and almost 2 percent of the world's 4,600 live mammal species. The largest of the dolphin family is the Orca, or killer whale, growing to 25 to 30 feet. The smallest of the dolphin species is the Hectors dolphin, growing to about 4.5 feet in length.

    Ancestry

    • Direct descendants of the Archaeocetes, scientists believes dolphins were once more semi-aquatic than aquatic. Carbon-dated fossils show these ancestor species were in possession of hind limbs that were much more than "limb buds." These appendages demonstrate dexterity and contain a jointed skeletal system. Over time, roughly 9 million years, these large feet-like structures became permanent flippers that are now the dolphin's fluke, or tail. Current theories have the ancient dolphin looking very much like an alligator, without the scales.

    Physiological Adaptation

    • The most widely accepted hypotheses as to why dolphins turned to life in the water is directly associated to a collective decision to take advantage of an unexplored ecological resource. The ocean offered a vast array of food sources and prey for dolphin, without their having to continue to engage in the immense competition occurring on land. This evolutionary process speaks not only to the physical adaptability of this mammal, but also to its intelligence.

    Intelligence

    • To get a true sense of when and how dolphins acquired their unique and telling intelligence, communication and physiologically related systems, we have to look very far back in time. About 55 million years ago dolphins developed their torpedo-like shape, current internal organs and exclusive vocal abilities. Considering humans have only been around for about 200,000 years, science accredits this extraordinarily long evolutionary span with the dolphins highly developed intelligence and communication skills.

    Physical Evolution

    • Also through evolutionary time, dolphins have been imparted with an elongated, telescoping skull that meets the spine at a 180-degree angle, as opposed to the 90-degree angle of most mammals. The skull, migrated from the original right angle, allows the nostrils to be on the top of the head. Recent studies believe these adaptations to be related to increased brain size and supplanted for the dolphin species to remain air-breathing.

      The study of molecular DNA proves today's dolphin cetaceans' closest living relative is the hippopotamus. Considering the hippo's amphibious acclimation and its more recent affinity for the ocean, it is easy to see how and why the dolphin underwent such drastic physiological changes.