He applied the “Page 99 Test” to his new book, Friendship: Development, Ecology, and Evolution of a Relationship, and reported the following:
Friendship imagines the human bond of friendship as a living organism and poses a number of questions that a natural historian might ask. How does friendship work? How does it develop and change in diverse environments? And how did it evolve? On page 99, I examine why people devote so much time and energy to making friends when in many societies they have ready-made support networks in the form of parents, brothers, sisters, aunts, uncles, and cousins. Based on case studies from a wide range of human groups, including foragers, subsistence farmers, and nomadic herders, I describe a recurring reason for preferring friends. Put simply, kin may not be in a position to provide the right kind of support. Consider the case of Basuto farmers in southern Africa:Learn more about Friendship at the publisher's website.A single Basuto household rarely commanded all of the four resources—oxen, land, seed, and food for workers—necessary for farming. To remedy this situation, households frequently entered into cooperative partnerships called seahlolo, whereby each household provided some combination of these resources. The two seahlolo partners were expected to work together and harvest together, dividing the crop equally. While classical views of rural, non-industrial societies suggest that Basuto farmers would make every effort to enter into seahlolo with kin, in the majority of cases they chose unrelated households.Based on accounts from Basuto farmers, Sandra Wallman, concludes that a key reason for preferring friends was that kin did not have the right resources to be good seahlolo partners. Specifically, two brothers may both own an ox, but neither owns necessary seed or land. Two cousins may possess seed, but no land or oxen. Similar problems arise in a wide variety of human societies.In a small village in Andalusia, Spain, a farmer may have no kinsmen with a sufficient leverage to plead his case in a water dispute. In Melanesia, a gardener may need to travel to other islands to acquire obsidian and high-quality pots. Among Orokaiva gardeners in Papua New Guinea, there may be no kin in safe areas when warfare breaks out near home.In each of these cases there are crucial gaps in the kin support network, and non-kin friends often provide a means to fill those gaps.
More generally, Page 99 captures a central concern in the book—understanding how human friendships articulate with other kinds of human relationships, such as those based on kin ties, sexual attraction, romantic attachment, and emotionally distant business-like transactions. Through such comparisons, the book identifies how friendship is a unique way of relating among humans.