Abstract
Facebook has become an international phenomenon (Back et al., 2010; Whitchurch, Wilson, and Gilbert, in press). Flying in the face of traditional social psychological principles such as propinquity (Lindzey and Byrne, 1968), social networking allows internet users closer functional distance with which to navigate their social world. The prevalence of Facebook means that a user's management of his or her social network yields a quantitative variable – number of friends. What is a typical number of friends? How do we stack up? We all wonder these questions, but Robin Dunbar has developed an idea that synthesizes two important elements: what the number is, and why the number is what it is.
Pointing out biological influences of behavior, Dunbar suggests that the size of the human neocortex dictates the number of friendships that we can maintain. The mean number of friendships that people across the world can effectively manage is 150, referred to as Dunbar's number. Dunbar's number includes kin and close friends, but it also includes acquaintances that one may not be close to, but would recognize and greet if encountered in public.
Related to Dunbar's number is the “circle of acquaintances,” which refers to the idea that humans have social networks that are structured based on multiples of three. For example, we have three to five very close friends. Next, we have a group of about 10 other people that we are slightly less close to. Then, a group of roughly 30 people whom we are even less close to. This structure follows a pattern based on multiples of three (i.e., 5, 15, 50, and 150). At each level, the number of friends within the circle remains stable. For that reason, there is the potential for old friends to be replaced by new friends. So, if someone develops an intimate relationship with a new person, an older friend will be bumped out of the closest-knit circle and replaced by the new friend.
Kanazawa (2002) proposed that humans have impressions of their social networks that can be fooled by viewing television shows such as dramas for females and the news for males. By this logic, Dunbar's number should be evidenced in quantitative relationships between number of Facebook friends and type of television shows viewed. Kanazawa suggested that currently there are more one-way relationships than ever before, in which one person knows or feels as though he or she knows someone else. For example, you may have formed an impression of Bill Clinton and Tony Blair, but it is unlikely that they have formed impressions of you.
The full title of the text hints that the overall theme revolves around two main areas: Dunbar's number, which has already been discussed, and other evolutionary quirks. The evolutionary quirks may best be described as fun, interesting, and odd facts about humans that can be explained by evolutionary theory. Humans are egocentric, focusing on self-relevant information (Fiske and Taylor, 2008). Thus, this book is of interest to all humans who think and behave.
Dunbar states that 0.5 percent of all men currently alive are related to the Mongol warrior king Genghis Khan of the thirteenth century. Furthermore, of the men whose ancestors are from the old Mongol empire in central Asia, there is a 1 in 12 chance that they are related to Genghis Khan. That section wonderfully illustrates the point that everyone alive today is likely related to some well-known historical figure, and outlines the evolutionary theory behind why this occurred.
Another interesting fact mentioned about most people alive today is that the majority cannot drink milk without serious health-related consequences. As babies, all humans drink milk. But after weaning, most humans' lactase gene switches off resulting in an inability to digest milk. For Caucasians of European decent, a genetic mutation prevents the lactase gene from switching off. So what gave rise to this mutation that is so common in Caucasians, yet so rare in other ethnicities? Ultraviolet light from the sun helps human skin synthesize vitamin D. Calcium is associated with this process, so by taking in more calcium, the body is better able to synthesize vitamin D. For individuals that live in an environment with low exposure to ultraviolet light such as northern Europe, the extra calcium intake from milk compensates for the lack of ultraviolet light. This is a great example of human adaptation to environmental conditions.
Dunbar also touches on the development of language, and compares human language to the grooming practices of monkeys and apes. It is noted that monkeys and apes groom one another to express commitment. According to Dunbar, human language is, “…a kind of grooming at a distance…” (p. 74). In other words, humans use language to communicate commitment, much in the same way that monkeys and apes use grooming to communicate commitment. Human language affords us the ability to communicate much more than commitment, but the grooming theory of communication is intriguing.
How Many Friends Does One Person Need? is an excellent, interesting read that is appropriate for a general audience's development of a familiarity with the concepts and research in evolutionary psychology. The transitions among formerly separate pieces of writing are seamless and are commonly bonded by the theme that human cognition and behavior are evolved and that by studying the quirks we gain insight into how these facets came to be. Scholars would do well to friend Mr. Dunbar, or at least read his book and feel like they know him. Friend us, Mr. Dunbar, for we enjoyed getting to know you.