Why can you say that members of a group are more closely related to one another than they are to members of another group?

Members of a group are often more closely related to one another due to shared genetic ancestry, which can be traced through common ancestors. This genetic similarity arises from their lineage and historical reproductive patterns. In contrast, members of a different group typically have different ancestral backgrounds, leading to greater genetic divergence. Thus, the closer the shared ancestry, the more likely it is that individuals within the same group exhibit similar genetic traits compared to those in other groups.