The ancestor of today’s dolphin appeared on Earth about 95 million years ago. Mesonix was a terrestrial animal that waded into shallow water to feed, had four legs and a body covered with hair. In the next 20 million years, Mesonix adapted to living in the water and forelegs became pectoral flippers while hind legs began to disappear. Vestigial hind limbs are still present in modern day dolphins in the form of rod-shaped pelvic bones and pectoral flippers house all the carpal and metacarpal bones of hands like yours and mine. As a result of evolution, the nostrils of early dolphins migrated from the nose to the top of the head to make it easier to breath while swimming or resting in the water.
The Tokyo Institute of Technology recently decoded the DNA sequences of the dolphin genome showing that these whales are closely related to cows, giraffes, pigs and antelope, with the closest being the hippo. The dolphin’s 3-chambered stomach functions the same way as the 4-chambered cow’s, providing more evidence of their link. Dr. David Busbee of Texas A & M University has discovered that dolphins and humans share many similar chromosomal similarities. Dolphins and whales have an excellent fossil record and they are one of the best examples of evolutionary transition showing their movement from land to water.