Answer:
Manatees' arm and finger bones are evidence that manatees share a common ancestor with land mammals.
Step-by-step explanation:
Manatees were aquatic mammals while humans are mainly land mammals. However, the presence of body parts or organs having similar structures in manatees and humans suggests that these two species of mammals shared a common ancestor. The arms and finger bones were also present in their common ancestors.
Humans and manatees diverged into different directions to become adapted to terrestrial and aquatic lifestyle respectively. Therefore, the forelimbs developed into flippers in manatees while the same do the function of holding objects in humans. These are called homologous structures.