The chances of aquatic mammals — like orcas, dolphins and whales — ever evolving to live on land again are almost nonexistent, a new study has found. Researchers discovered that the adaptations that allowed these animals to live in water have passed an evolutionary threshold that marks the point of no return to terrestrial life.
Between 350 million and 400 million years ago, the first fish crawled out of the water and onto land. These awkward vertebrates had the beginnings of limbs that allowed them to trundle around, and subsequent generations evolved to become the tetrapod species we see today.
