Mammals are though to be so adaptable in the regard of switching from land to sea, that a possible transitional species may exist today. In the Tokelau Islands of the Pacific, a species of hog is known to forage for crustaceans in the low tide coral reefs. These hogs have adapted the ability to swim with their head submerged.

Fossil records of the intermediary species between whales and their ancestors are relatively intact. With all this evidence, scientists believe that whales are the great-grandchildren of species' related to wolves. At one time, the whales were coastal creatures who dwelled near the coast and picked off monkeys from tree branches in mangrove-like terrains.