Passage Summary: Chimps that act nice to their friends get protected more often. Since humans also protect the people they like, affection must do the same thing for both species.

Conclusion: Affection serves the same sociological purpose in chimp and human communities.

Reasoning: Chimps that show affection are defended more often by their group, and humans are more willing to protect those they feel affection for.

Analysis: There is a subtle but critical gap between 'displaying' affection and 'feeling' it. The argument notes that chimps who display affection are protected, but it assumes that the protection is actually motivated by the defenders' feelings of affection. If the defenders protect the affectionate chimp for some other reason—like social status or simple reciprocity—the comparison to human affection falls apart. Look for an answer that links the defenders' actions to their own internal feelings of affection.