Peace Among Primates (Part 2)

(Edi­tor’s Note: A few days ago we pub­lished the first install­ment of this Peace Among Pri­mates series, by neu­ro­sci­en­tist Robert Sapol­sky. Today we pub­lish the sec­ond install­ment. Next Sat­ur­day, April 19th, you can come back and read the third and final part in the series.)

Peace Among Pri­mates (Part 2)

Any­one who says peace is not part of human nature knows too lit­tle about pri­mates, includ­ing ourselves.

–By Robert M. Sapolsky

Left behind

In the ear­ly 1980s, “For­est Troop,” a group of savan­na baboons I had been studying—virtually liv­ing with—for years, was going about its busi­ness in a nation­al park in Kenya when a neigh­bor­ing baboon group had a stroke of luck: Its ter­ri­to­ry encom­passed a tourist lodge that expand­ed its oper­a­tions and, con­se­quent­ly, so did the amount of food tossed into its garbage dump. Baboons are omniv­o­rous, and this “Garbage Dump Troop” was delight­ed to feast on left­over drum­sticks, half-eat­en ham­burg­ers, rem­nants of choco­late cake, and any­thing else that wound up there. Soon they had shift­ed to sleep­ing in the trees imme­di­ate­ly above the pit, descend­ing each morn­ing just in time for the day’s dump­ing of garbage. (They soon got quite obese from the rich diet and lack of exer­cise, but that is anoth­er sto­ry.) The devel­op­ment pro­duced near­ly as dra­mat­ic a shift in the social behav­ior of For­est Troop. Each morn­ing, approx­i­mate­ly half of its adult males would infil­trate Garbage Dump Troop’s ter­ri­to­ry, descend­ing on the pit in time for the day’s dump­ing and bat­tling the res­i­dent males for access to the garbage. The par­tic­u­lar For­est Troop males who did this shared two traits: They were espe­cial­ly com­bat­ive (which was nec­es­sary to get the food away from the oth­er baboons), and they were not very inter­est­ed in social­iz­ing (the raids took place ear­ly in the morn­ing, dur­ing the hours when the bulk of a savan­na baboon’s dai­ly com­mu­nal groom­ing occurs).

Soon after­ward, tuber­cu­lo­sis, a dis­ease that moves with dev­as­tat­ing speed and sever­i­ty in non­hu­man pri­mates, broke out in Garbage Dump Troop. Over the next year, most of its mem­bers died, as did all of the males from For­est Troop who had for­aged at the dump. (Con­sid­er­able sleuthing ulti­mate­ly revealed that the dis­ease had come from taint­ed meat in the garbage dump. There was lit­tle ani­mal-to-ani­mal trans­mis­sion of the tuber­cu­lo­sis, and so the dis­ease did not spread in For­est Troop beyond the garbage eaters.) The results were that For­est Troop was left with males who were less aggres­sive and more social than aver­age, and the troop now had dou­ble its pre­vi­ous female-to-male ratio.

The social con­se­quences of these changes were dra­mat­ic. There remained a hier­ar­chy among the For­est Troop males, but it was far loos­er than before. Com­pared with oth­er, more typ­i­cal savan­na baboon groups, high-rank­ing males rarely harassed sub­or­di­nates and occa­sion­al­ly even relin­quished con­test­ed resources to them. Aggres­sion was less fre­quent, par­tic­u­lar­ly against third par­ties. And rates of affil­ia­tive behav­iors, such as males and females groom­ing each oth­er or sit­ting togeth­er, soared. There were even instances, now and then, of adult males groom­ing each other—a behav­ior near­ly as unprece­dent­ed as baboons sprout­ing wings.

This unique social milieu did not arise mere­ly as a func­tion of the skewed sex ratio (with half the males hav­ing died); oth­er pri­ma­tol­o­gists have occa­sion­al­ly report­ed on troops with sim­i­lar ratios but with­out a com­pa­ra­ble social atmos­phere. What was key was not just the pre­dom­i­nance of females but the type of male who remained. The demo­graph­ic disaster—what evo­lu­tion­ary biol­o­gists term a “selec­tive bottleneck”—had pro­duced a savan­na baboon troop quite dif­fer­ent from what most experts would have anticipated.

But the largest sur­prise did not come until some years lat­er. Female savan­na baboons spend their lives in the troop into which they are born, where­as males leave their birth troop around puber­ty; a troop’s adult males have thus all grown up else­where and immi­grat­ed as ado­les­cents. By the ear­ly 1990s, none of the orig­i­nal low aggression/high affil­i­a­tion males of For­est Troop’s tuber­cu­lo­sis peri­od was still alive; all of the group’s adult males had joined after the epi­dem­ic. Despite this, the troop’s unique social milieu persisted—as it does to this day, some 20 years after the selec­tive bot­tle­neck. In oth­er words, ado­les­cent males that enter For­est Troop after hav­ing grown up else­where wind up adopt­ing the unique behav­ioral style of the res­i­dent males. As defined by both anthro­pol­o­gists and ani­mal behav­ior­ists, “cul­ture” con­sists of local behav­ioral vari­a­tions, occur­ring for non­genet­ic and none­co­log­i­cal rea­sons, that last beyond the time of their orig­i­na­tors. For­est Troop’s low aggression/high affil­i­a­tion soci­ety con­sti­tutes noth­ing less than a multi­gen­er­a­tional benign culture.

Con­tin­u­ous study of the troop has yield­ed some insights into how its cul­ture is trans­mit­ted to new­com­ers. Genet­ics obvi­ous­ly plays no role, nor appar­ent­ly does self-selec­tion: Ado­les­cent males that trans­fer into the troop are no dif­fer­ent from those that trans­fer into oth­er troops, dis­play­ing on arrival sim­i­lar­ly high rates of aggres­sion and low rates of affil­i­a­tion. Nor is there evi­dence that new males are taught to act in benign ways by the res­i­dents. One can­not rule out the pos­si­bil­i­ty that some obser­va­tion­al learn­ing is occur­ring, but it is dif­fi­cult to detect, giv­en that the dis­tinc­tive fea­ture of this cul­ture is not the per­for­mance of a unique behav­ior but the per­for­mance of typ­i­cal behav­iors at atyp­i­cal­ly extreme rates.

To date, the most inter­est­ing hint about the mech­a­nism of trans­mis­sion is the way recent­ly trans­ferred males are treat­ed by For­est Troop’s res­i­dent females. In a typ­i­cal savan­na baboon troop, new­ly trans­ferred ado­les­cent males spend years slow­ly work­ing their way into the social fab­ric; they are extreme­ly low ranking—ignored by females and not­ed by adult males only as con­ve­nient tar­gets for aggres­sion. In For­est Troop, by con­trast, new male trans­fers are inun­dat­ed with female atten­tion soon after their arrival. Res­i­dent females first present them­selves sex­u­al­ly to new males an aver­age of 18 days after the males arrive, and they first groom the new males an aver­age of 20 days after they arrive, where­as nor­mal savan­na baboons intro­duce such behav­iors after 63 and 78 days, respec­tive­ly. Fur­ther­more, these wel­com­ing ges­tures occur more fre­quent­ly in For­est Troop dur­ing the ear­ly post-trans­fer peri­od, and there is four times as much groom­ing of males by females in For­est Troop as else­where. From almost the moment they arrive, in oth­er words, new males find out that in For­est Troop, things are done differently.

At present, I think the most plau­si­ble expla­na­tion is that this troop’s spe­cial cul­ture is not passed on active­ly but sim­ply emerges, facil­i­tat­ed by the actions of the res­i­dent mem­bers. Liv­ing in a group with half the typ­i­cal num­ber of males, and with the males being nice guys to boot, For­est Troop’s females become more relaxed and less wary. (This is so, in part, because in a typ­i­cal baboon troop, a male who los­es a dom­i­nance inter­ac­tion with anoth­er male will often attack a female in frus­tra­tion.) As a result, they are more will­ing to take a chance and reach out social­ly to new arrivals, even if the new guys are typ­i­cal jerky ado­les­cents at first. The new males, in turn, find­ing them­selves treat­ed so well, even­tu­al­ly relax and adopt the behav­iors of the troop’s dis­tinc­tive social milieu.


(To be con­tin­ued, in a third and final install­ment, on Sat­ur­day April 19th).

Robert SapolskyRobert M. Sapol­sky, Ph.D., is the John A. and Cyn­thia Fry Gunn Pro­fes­sor of Bio­log­i­cal Sci­ences and a pro­fes­sor of neu­rol­o­gy and neu­ro­log­i­cal sci­ences at Stan­ford Uni­ver­si­ty. He wrote the clas­sic Why Zebras Don’t Get Ulcers: An Updat­ed Guide to Stress, Stress Relat­ed Dis­eases and Cop­ing. His most recent book is Mon­key­luv: And Oth­er Essays on Our Lives as Ani­mals. A longer ver­sion of this essay appeared in For­eign Affairs. We bring you this post thanks to our col­lab­o­ra­tion with Greater Good Mag­a­zine, a UC-Berke­ley-based quar­ter­ly mag­a­zine that high­lights ground break­ing sci­en­tif­ic research into the roots of com­pas­sion and altruism.


  1. Michelle B on April 12, 2008 at 3:55

    Fas­ci­nat­ing post.

    How much can these obser­va­tions of pri­mate cul­ture be extrap­o­lat­ed to human?

  2. Michelle B on April 12, 2008 at 4:00

    Let me rephrase that ques­tion: How can one apply these obser­va­tions regard­ing baboon soci­ety to human? What exam­ple in human soci­ety can be used to show a sim­i­lar social mech­a­nism? Per­haps, the intro­duc­tion of women work­ers into once male-dom­i­nat­ed occupations?

    (No won­der Charleston Hes­ton bemoaned the fate of the white tra­di­tion­al male role, geesh, it does­n’t stand a chance!)

  3. Robert on April 12, 2008 at 10:37

    I am great­ly sad­dened to recent­ly hear that “For­est Troop” was slaugh­tered by poach­ers and with the ille­gal help of a Park Ranger. I can only imag­ine the impact this might have on Dr. Sapol­sky. I am tru­ly saddened.

  4. Alvaro on April 13, 2008 at 9:14

    Robert, yes, I am sure that was a hard moment. Many lessons to be learned.

    Michelle: great ques­tion. There are many rel­e­vant impli­ca­tions. Let me pro­pose a few:
    1) The role of our envi­ron­ment in influ­enc­ing our behav­iors, vs. the usu­al­ly accept­ed more genet­ic-based “deter­min­ism”
    2) The impor­tance of ensur­ing vir­tu­ous, pos­i­tive feed­back loops.
    3) And, yes, this exam­ple sug­gests that expand­ing the role of females in a soci­ety may cre­ate a more har­mo­nious atmosphere…perhaps call­ing for more females in top busi­ness and polit­i­cal ranks?
    4) In terms of the ” intro­duc­tion of women work­ers into once male-dom­i­nat­ed occu­pa­tions”, it would be fas­ci­nat­ing to com­pare the cul­ture of three types of occu­pa­tions: a) most­ly male, b) bal­anced male/ female, c) most­ly female. What would you say?
    5) Final­ly, a pure­ly per­son­al spec­u­la­tion along the lines that genet­ics is not fate…: who is exhibit­ing more of those “female” traits in this US polit­i­cal campaign?

  5. Al Fin on April 13, 2008 at 10:54

    A more straight­for­ward com­par­i­son might sug­gest that human females should be more sex­u­al­ly recep­tive to the human males around them.

    This is the oppo­site of the trend insti­gat­ed by rad­i­cal feminism–which may explain the increase in aggres­sion in some mod­ern soci­eties. For exam­ple, the free­way sys­tems of California.

    More avail­able sex might go a long way toward mit­i­gat­ing human violence.

  6. Michelle B on April 14, 2008 at 6:28

    @Al Fin, Fem­i­nism encour­ages sex edu­ca­tion, birth con­trol, and choice, not reduc­tion of sex­u­al recep­tiv­i­ty. If a woman feels empow­ered and safe, she is more recep­tive to life, includ­ing hav­ing sex.

    Patri­archy prob­a­bly has more to do with why women may be so uptight about sex, as they are pun­ished both phys­i­cal­ly and emo­tion­al­ly if they act ‘slut­like.’

  7. Michelle B on April 14, 2008 at 6:31

    Alvaro, nice col­lec­tion of points. Are you say­ing that Oba­ma could teach a few things to Clin­ton about being a woman? (tee­hee)

    Regard­ing your point 4, if that research has not already been done, it needs to be.

  8. Alvaro on April 15, 2008 at 12:50

    Michelle: probably…and it seems Clin­ton could teach Oba­ma some hunt­ing tricks…

  9. Ben Hemmens on February 13, 2009 at 12:33

    I sus­pect the baboons got peace­ful because of Sapol­sky hang­ing around, spread­ing those laid back vibes ;-)

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SHARPBRAINS is an independent think-tank and consulting firm providing services at the frontier of applied neuroscience, health, leadership and innovation.

English About SharpBrains

SHARPBRAINS es un think-tank y consultoría independiente proporcionando servicios para la neurociencia aplicada, salud, liderazgo e innovación.

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