Final answer:
Fossils and anatomical structures provide evidence for the evolutionary history of whales, highlighting their terrestrial ancestry and subsequent adaptations for aquatic life. Vestigial structures and homologies are key areas of study for understanding their phylogeny.
Step-by-step explanation:
Scientists have used various types of evidence to trace the evolutionary history of aquatic mammals, particularly whales. One pivotal piece of evidence comes from the structure of fossilized bones, which allows scientists to see the progression and transition of species over time. The fossil record, including that of well-known ancestors of modern whales like Pakicetus and Rodhocetus, has been instrumental in piecing together these evolutionary relationships. Rodhocetus, with its unique type of ankle bone typically found in land animals, offers evidence that modern whales evolved from land-dwelling ancestors.
Another evidence type is anatomy and embryology, which examines homologous structures across different species. For example, the similar construction of the bones in the appendages of a human, dog, bird, and whale points to a common ancestor. Additionally, the concept of vestigial structures, like the presence of traces of pelvic bones in whales, supports the theory that these aquatic creatures evolved from organisms that had hindlimbs.
Together, these evidences contribute to our understanding of animal phylogeny and help scientists construct phylogenetic evolutionary tree diagrams, showcasing the morphological and genetic relationships between species and their shared evolutionary paths.