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Peace Among Primates- by Robert Sapolsky

(Editor’s Note: One of the most orig­i­nal minds we have ever encoun­tered is that of Robert Sapol­sky, the Stan­ford-based neu­ro­sci­en­tist, pri­ma­tol­o­gist, author of A Primate’s Mem­oir, and more. We high­ly rec­om­mend most of his books. Above all, for any­one inter­est­ed in brain health, this is a must read and very fun: Why Zebras Don't Have Ulcers- Robert SapolskyWhy Zebras Don’t Get Ulcers: An Updat­ed Guide To Stress, Stress Relat­ed Dis­eases, and Cop­ing. We are hon­ored to bring you a guest arti­cle series by Robert Sapol­sky, thanks to our col­lab­o­ra­tion with Greater Good Mag­a­zine.)

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Peace Among Pri­mates

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

–By Robert M. Sapol­sky

It used to be thought that humans were the only sav­age­ly vio­lent pri­mate.  “We are the only species that kills its own, nar­ra­tors intoned por­ten­tous­ly in nature films sev­er­al decades ago. That view fell by the way­side in the 1960s as it became clear that some oth­er pri­mates kill their fel­lows aplen­ty. Males kill; females kill. Some use their tool­mak­ing skills to fash­ion big­ger and bet­ter cud­gels. Oth­er pri­mates even engage in what can only be called war­fare, orga­nized, proac­tive group vio­lence direct­ed at oth­er pop­u­la­tions.

Yet as field stud­ies of pri­mates expand­ed, what became most strik­ing was the vari­a­tion in social prac­tices across species. Yes, some pri­mate species have lives filled with vio­lence, fre­quent and var­ied. But life among oth­ers is filled with com­mu­ni­tar­i­an­ism, egal­i­tar­i­an­ism, and coop­er­a­tive child rear­ing.Pat­terns emerged. In less aggres­sive species, such as gib­bons or mar­mosets, groups tend to live in lush rain forests where food is plen­ti­ful and life is easy. Females and males tend to be the same size, and the males lack sec­ondary sex­u­al mark­ers such as long, sharp canines or gar­ish col­or­ing. Cou­ples mate for life, and males help sub­stan­tial­ly with child care. In vio­lent species, such as baboons and rhe­sus mon­keys, the oppo­site con­di­tions pre­vail.

The most dis­qui­et­ing fact about the vio­lent species was the appar­ent inevitabil­i­ty of their behav­ior. Cer­tain species seemed sim­ply to be the way they were, fixed prod­ucts of the inter­play of evo­lu­tion and ecol­o­gy, and that was that. And although human males might not be inflex­i­bly polyg­a­mous or out­fit­ted with bright red butts and six-inch canines designed for tooth-to-tooth com­bat, it was clear that our species had at least as much in com­mon with the vio­lent pri­mates as with the gen­tle ones. “In their nature thus became “in our nature.” This was the humans-as-killer-apes the­o­ry pop­u­lar­ized by the writer Robert Ardrey, accord­ing to which humans have as much chance of becom­ing intrin­si­cal­ly peace­ful as they have of grow­ing pre­hen­sile tails.

That view always had lit­tle more sci­en­tif­ic rig­or than a Plan­et of the Apes movie, but it took a great deal of field research to fig­ure out just what should sup­plant it. After decades of more work, the pic­ture has become quite inter­est­ing. Some pri­mate species, it turns out, are indeed sim­ply vio­lent or peace­ful, with their behav­ior dri­ven by their social struc­tures and eco­log­i­cal set­tings. More impor­tant­ly, how­ev­er, some pri­mate species can make peace despite vio­lent traits that seem built into their natures. The chal­lenge now is to fig­ure out under what con­di­tions that can hap­pen, and whether humans can man­age the trick our­selves.

Old pri­mates and new tricks

To an over­whelm­ing extent, the age-old “nature ver­sus nur­ture” debate is sil­ly. The action of genes is com­plete­ly inter­twined with the envi­ron­ment in which they func­tion; in a sense, it is point­less to even dis­cuss what gene X does, and we should con­sid­er instead only what gene X does in envi­ron­ment Y. Nonethe­less, if one had to pre­dict the behav­ior of some organ­ism on the basis of only one fact, one might still want to know whether the most use­ful fact would be about genet­ics or about the envi­ron­ment.

Two clas­sic stud­ies have shown that pri­mates are some­what inde­pen­dent from their “natures.” In the ear­ly 1970s, a high­ly respect­ed pri­ma­tol­o­gist named Hans Kum­mer was work­ing in a region of Ethiopia con­tain­ing two species of baboons with marked­ly dif­fer­ent social sys­tems. Savan­na baboons live in large troops, with plen­ty of adult females and males. Hamadryas baboons, in con­trast, have a more com­plex and quite dif­fer­ent mul­ti­level soci­ety. When con­front­ed with a threat­en­ing male, the females of the two species react dif­fer­ent­ly: A hamadryas baboon pla­cates the male by approach­ing him, where­as a savan­na baboon can only run away if she wants to avoid injury.

Kum­mer con­duct­ed a sim­ple exper­i­ment, trap­ping an adult female savan­na baboon and releas­ing her into a hamadryas troop and trap­ping an adult female hamadryas and releas­ing her into a savan­na troop. The females who were dropped in among a dif­fer­ent species ini­tial­ly car­ried out their species-typ­i­cal behav­ior, a major faux pas in the new neigh­bor­hood. But grad­u­al­ly, they absorbed the new rules. How long did this learn­ing take? About an hour. In oth­er words, mil­len­nia of genet­ic dif­fer­ences sep­a­rat­ing the two species, a life­time of expe­ri­ence with a cru­cial social rule for each female and a minis­cule amount of time to reverse course com­plete­ly.

The sec­ond exper­i­ment was set up by Frans de Waal of Emory Uni­ver­si­ty and his stu­dent Denise Johanow­icz in the ear­ly 1990s, work­ing with two macaque mon­key species. By any human stan­dards, male rhe­sus macaques are unap­peal­ing ani­mals. Their hier­ar­chies are rigid, those at the top seize a dis­pro­por­tion­ate share of the spoils, they enforce this inequity with fero­cious aggres­sion, and they rarely rec­on­cile after fights. In con­trast, male stump tail macaques, which share almost all of their genes with their rhe­sus macaque cousins, dis­play much less aggres­sion, loos­er hier­ar­chies, more egal­i­tar­i­an­ism, and more behav­iors that pro­mote group cohe­sion.

Work­ing with cap­tive pri­mates, de Waal and Johanow­icz cre­at­ed a mixed-sex social group of juve­nile macaques, com­bin­ing rhe­sus and stump tails togeth­er. Remark­ably, instead of the rhe­sus macaques bul­ly­ing the stump tails, over the course of a few months the rhe­sus males adopt­ed the stump tails social style, even­tu­al­ly even match­ing the stump tails high rates of rec­on­cil­ia­to­ry behav­ior. It so hap­pens, more­over, that stump tails and rhe­sus macaques use dif­fer­ent ges­tures when rec­on­cil­ing. The rhe­sus macaques in the study did not start using the stump tails rec­on­cil­ia­to­ry ges­tures, but rather increased the inci­dence of their own species-typ­i­cal ges­tures. In oth­er words, they were not mere­ly imi­tat­ing the stump tails behav­ior; they were incor­po­rat­ing the con­cept of fre­quent rec­on­cil­i­a­tion into their own social prac­tices. Final­ly, when the new­ly warm-and-fuzzy rhe­sus macaques were returned to a larg­er, all-rhe­sus group, their new behav­ioral style per­sist­ed.

This is noth­ing short of extra­or­di­nary. But it brings up one fur­ther ques­tion: When those rhe­sus macaques were trans­ferred back into the all-rhe­sus world, did they spread their insights and behav­iors to the oth­ers? Alas, they did not at least not with­in the rel­a­tive­ly short time they were stud­ied. For that, we need to move on to a final case.

(To be con­tin­ued, in a sec­ond install­ment on Sat­ur­day April 12th).

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.

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