Daniel J. Hruschka is an Assistant Professor in the Arizona State University's School of Human Evolution and Social Change.

List of Illustrations
List of Boxes
Acknowledgments
Introduction: The Adaptive Significance of Friendship
1. An Outline of Friendship
2. Friendships across Cultures
3. Friendship and Kinship
4. Sex, Romance, and Friendship
5. Friendship: Childhood to Adulthood
6. The Development of Friendships
7. Friendship, Culture, and Ecology
8. Playing with Friends
Conclusion
Appendix A: Ethnographic Data and Coding
Appendix B: Mathematical Models for Chapter 8
Appendix C: D-Statistics for Studies Cited
Notes
References
Index

Friends-they are generous and cooperative with each other in ways that appear to defy standard evolutionary expectations, frequently sacrificing for one another without concern for past behaviors or future consequences. In this fascinating multidisciplinary study, Daniel J. Hruschka synthesizes an array of cross-cultural, experimental, and ethnographic data to understand the broad meaning of friendship, how it develops, how it interfaces with kinship and romantic relationships, and how it differs from place to place. Hruschka argues that friendship is a special form of reciprocal altruism based not on tit-for-tat accounting or forward-looking rationality, but rather on mutual goodwill that is built up along the way in human relationships.