Answer
The fossil record provides evidence for the close relationship between whales and even-toed ungulates (Artiodactyla).
Molecular data also supports the hypothesis of a close relationship between whales and even-toed ungulates.
Taken together, the fossil record and molecular data provide strong support for the hypothesis that whales are closely related to even-toed ungulates, and that they share a common ancestor that lived around 50 million years ago.
Work Step by Step
The fossil record provides evidence for the close relationship between whales and even-toed ungulates (Artiodactyla). Fossil whales from the Eocene epoch (around 50 million years ago) have been found with several characteristics that suggest a close relationship to even-toed ungulates, such as elongated ankle bones and teeth with multiple cusps. Additionally, fossil evidence shows a gradual transition from land-dwelling ancestors with legs to fully aquatic forms, providing further support for the hypothesis of a common ancestor with even-toed ungulates.
Molecular data also supports the hypothesis of a close relationship between whales and even-toed ungulates. DNA sequencing studies have shown that whales and hippos (a type of even-toed ungulate) share several molecular markers that suggest a common ancestor. Specifically, both groups have a deletion in a gene that encodes for a protein involved in limb development, which is thought to be a key adaptation in the transition to aquatic life.
