Marine mammals possess systems which are entirely peculiar to themselves. These are designed in the best way for the environment they live in.

Whales and dolphins belong to the order of marine mammals known as Cetacea. These creatures are classified as mammals because, just like land-dwelling mammals, they give live birth to their young and nurse them, they have lungs to breathe with, and they regulate their body temperature. For evolutionists, the origin of marine mammals has been one of the most difficult issues to explain. In many evolutionist sources, it is asserted that the ancestors of cetaceans left the land and evolved into marine mammals over a long period of time. Accordingly, marine mammals followed a path contrary to the transition from water to land, and underwent a second evolutionary process, returning to the water. This theory both lacks paleontological evidence and is self-contradictory. Thus, evolutionists have been silenced on this issue for a long time.

However, an evolutionist hype about the origin of marine mammals broke out in the 90's, argued to be based on some new fossil findings of the 80's like Pakicetus and Ambulocetus. These evidently quadrupedal and terrestrial extinct mammals were alleged to be the ancestors of whales and thus many evolutionist sources did not hesitate to call them "walking whales." (In fact the full name, Ambulocetus natans, means "walking and swimming whale.") Popular means of evolutionist indoctrination further vulgarized the story. National Geographic in its November 2001 issue, finally declared the full evolutionist scenario on the "Evolution of Whales."

Nevertheless, the scenario was based on evolutionist prejudice, not scientific evidence.