Whales return to the sea
A four-legged land mammal becomes the largest animal ever
See it on the timeline →In depth
The transition from Pakicetus through Ambulocetus and Rodhocetus to Basilosaurus is among the best-documented in palaeontology, with intermediates showing every step. The key evidence is the ear: the distinctive thickened ear bone of whales is already present in the land-dwelling forms. Wadi al-Hitan in Egypt, the Valley of the Whales, is a World Heritage site with hundreds of skeletons, several retaining tiny hind limbs. The blue whale, which evolved much later when nutrient-rich polar seas appeared, is the largest animal that has ever lived — larger than any dinosaur, because water carries the weight.
For children
Whales are mammals — they breathe air and give milk. Their ancestors were four-legged animals the size of a wolf that lived by riverbanks. Step by step the legs became flippers and the tail a horizontal fluke. In Egypt lies an entire valley full of fossils of the in-between forms.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org