Humans, mice, and giraffes have seven vertebrae in their necks. What can scientists conclude from this observation?
1. each animal independently evolved this trait
2. all vertebrates have seven vertebrates in their necks
3. humans, mice, and giraffes have the same number of bones
4. these animals descended from a common ancestor
4. these animals descended from a common ancestor
This observation suggests that humans, mice, and giraffes share a common evolutionary ancestor who had seven vertebrae in their necks, and this trait has been passed down through generations.