Final answer:
Shared ancestral characters are traits present in both the outgroup and the ingroup that predate their divergence from a common ancestor.
Step-by-step explanation:
Shared ancestral characters are traits that are present in both the outgroup and the ingroup and were inherited from a common ancestor. These traits are considered ancestral because they existed before the divergence of both groups. An example of a shared ancestral character is the presence of vertebrae in both humans and fish, indicating that this trait originated in their common ancestor.