How Many Friends Does One Person Need?: Dunbar’s Number and Other Evolutionary Quirks

Whyare we the way we are?

Thatsimple question has bedevilled humanity since the dawn of recorded history,provoking various answers from philosophers, mystics, theologians, fabulists,humorists, cynics, politicians, and, only in the last 300 years or so, fromnaturalists and scientists.  The latestdiscipline that seeks to unriddle the mysteries of human behavior andmentality, abilities and customs, is that of evolutionary biology, orevolutionary anthropology.  Taking athoroughly up-to-date Darwinism as their core set of tenets, thesepractitioners seek to tease out the formative influences from our hominidpast—and beyond—that endowed us with ingrained behaviors and modes of thoughtthat often translate directly into the institutions and cultural practices ofour everyday lives.

RobinDunbar is one such fellow, so successful at the task that he’s had what seemsto be an invariant natural fact named after him.  “Dunbar’s Law” holds as its mostbasic formulation that the average human can sustain no more than 150relatively close friends and relatives in any kind of practical and usefulnetwork.  (The law scales up and down fordifferent kinds of groups.)  Over thepast fifteen years Dunbar’s been explicating similar nooks and crannies ofevolutionary biology in such periodicals as New Scientist and the Scotsman.  Now he gathers up these pieces into onefascinating volume that ranges widely across time, space and humanpractices.  As Dunbar says at one point,”Evolution has saddles us with a whole series of cheap chemical tricksthat play a far more important part in our behaviour than most of us would liketo think.”

Tossingoff light-hearted examinations of such fairly innocent topics as why we kissand why all babies look very much alike, Dunbar is unafraid to tackle sensitiveand controversial issues as well.  Theseessays deal with race, gender, intelligence, class, and nationality indispassionate and unflinching  ways thatdo not seek to cushion hard facts with mealy-mouthed sanctimony.  In “Farewell, Cousins,” a look atextinction events, Dunbar forthrightly addresses the overbreeding of our ownspecies, and admonishes, “We really do need to get the world’s populationgrowth seriously into reverse.” When’s the last time you heard any politician or preacher say such athing—at least from a scientific, non-ethnic-cleansing standpoint?

Dunbaris cheerfully mordant about our tendency to apply the wrong yardstick and toolto just about any given situation, thus triggering a host of unintended consequences.  The chapter titled “Stone AgePsychology” opines that “We can expect much of our behaviour to bedeeply out of kilter with the circumstances we find ourselves in now.  In fact, maladapted, not to put too fine agloss on it.”  But he also finds muchhope and promise in the plastic nature of our minds, placing great stock in ourcapacity for “intentionality,” the ability to run virtual simulationsof the minds of others, an ability we share with no other species.  (He identifies six levels of intentionalityin Shakespeare’s work, one level more than most of us employ.)  Far from being a catalogue of gloom and doom,this book leaves the reader marvelling at how far homo sapiens has come,and how far we might yet ascend.

Aslagniappe for American readers, Dunbar’s essential endearing Britishness is ofton display.  “So how much time didyou waste yesterday wittering away nineteen to the dozen?”  It’s a test of intentionality to parse thatone!


The Speculator

Paul Di Filippo’s column The Speculator appears monthly in the Barnes & Noble Review.  He is the author of several acclaimed novels and story collections, including Fractal Paisleys, Little Doors, Neutrino Drag, and Fuzzy Dice.