Marine Mammals' Evolutionary Journey: No Turning Back to Land

A new study has found that fully-aquatic marine mammals, such as dolphins and orcas, are highly unlikely to evolve to live on land again. The adaptations that allowed these animals to thrive in water have passed an evolutionary threshold, making the transition to terrestrial life virtually impossible. The study examined over 5,600 mammal species and found that once a certain threshold of aquatic adaptations has been crossed, it becomes irreversible. The researchers concluded that the chances of fully aquatic animals, like whales and dolphins, returning to land are almost nonexistent.