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Warriors don’t always get the girl

May 12 , 2009
Courtesy Penn State University
and World Science staff

Some an­thro­po­l­o­gists have con­sid­ered ag­gres­sive be­hav­ior among cer­tain tri­bal peo­ples as a way for men to ob­tain more wives and chil­dren. But an­thro­po­l­o­gists work­ing in Ec­ua­dor among the Wao­rani peo­ple have found that some­times the ma­cho guy does­n’t do bet­ter. 

Waorani man with a blow­gun. Im­age court­esy of James Yost, La­ti­go Ranch, Kremm­ling, Colo.
In 1988, the U.S. an­thro­po­lo­g­ist Na­po­le­on Chag­non “pub­lished ev­i­dence that among the fa­mously war­like Yano­ma­mo of Ven­e­zue­la, men who had par­ti­ci­pated in a hom­i­cide had sig­nif­i­cantly more wives and chil­dren than their less war­like brethren,” said an­thro­po­lo­g­ist Ste­phen Beck­er­man of Penn State Uni­ver­s­ity. 

Yet “our re­search among the Wao­rani in­di­cates that more ag­gres­sive war­riors have low­er in­di­ces of re­pro­duc­tive suc­cess than less war­like men.”

Chagnon took con­si­der­able crit­i­cism for what op­po­nents con­sid­ered his sug­ges­tion that vi­o­lence was a nat­u­ral, an­ces­tral hu­man way of life. But Beck­er­man does­n’t con­test Chag­non’s find­ings; he in­stead ar­gues that the Ya­no­ma­mo and Wao­ra­ni have two very dif­fer­ent situa­t­ions.

The Wao­rani are rain­for­est hor­ti­cul­tur­alists and for­agers. When the first peace­ful con­tact oc­curred in 1958, they num­bered about 500 peo­ple liv­ing in an ar­ea the size of New Jer­sey be­tween the Napo and Cu­raray riv­ers in the Am­a­zon ba­sin east of the An­des. Their abun­dant re­sources of­ten at­tracted out­siders, who were promptly killed if found. 

War­fare and mur­der were com­mon among the Wao­rani, who are known to be more war­like than the Yano­ma­mo, ac­cord­ing to Beck­er­man and col­leagues. The Wao­rani prac­ticed their vi­o­lence on each oth­er as well as on out­siders. Even­tu­al­ly, over a per­i­od of 14 years, mis­sion­ar­ies pac­i­fied the Wao­rani. Ag­gres­sive war­fare and raid­ing are now al­most gone.

“In light of the doc­u­mented abun­dance of wild re­sources, re­source lim­ita­t­ion can­not be con­sid­ered the cause of war­fare among the Wao­rani,” said Beck­er­ma­n. 

Beck­er­man and col­leagues looked at how a ma­n’s par­ticipa­t­ion in raid­ing cor­re­lates with his sur­vi­vor­ship and that of his wives, the num­ber of his wives and the num­ber of chil­dren he pro­duced and their sur­vi­vor­ship. 

The re­search­ers in­ter­viewed men in 23 set­tle­ments. They in­ter­viewed any man old enough to have ex­pe­ri­enced war­fare be­fore the pa­cif­ica­t­ion that could be found and who agreed to the in­ter­view. The re­search­ers col­lect­ed Wao­rani men’s ge­nealo­gies, re­pro­duc­tive his­to­ry, nar­ra­tive per­son­al life his­to­ry and war­fare his­to­ry. The raid­ing database con­tained 95 men. Beck­er­man and his col­leagues re­port their re­search in this week’s edi­tion of the Pro­ceed­ings of the Na­tional Acad­e­my of Sci­ences on­line. 

“Our sam­ple of war­riors in­cludes both liv­ing and dead men,” said Beck­er­ma­n. “We ranked ag­gres­sion by the num­ber of raids they par­ti­ci­pated in. Our anal­y­sis is free of the prob­lem caused by the in­her­ent cor­rela­t­ion of the war­rior’s age with both par­ticipa­t­ion in raids and re­pro­duc­tive suc­cess.”

The re­search­ers found that more ag­gres­sive men do not ac­quire more wives than milder men. They do not have more chil­dren and their wives and chil­dren do not sur­vive long­er. In fact, war­like men have few­er chil­dren who sur­vive to re­pro­duc­tive age.

Why do these re­sults dif­fer from Chagnon’s and why are Wao­rani men so bel­li­cose when there ap­pears to be no ben­e­fit? The re­search­ers sug­gest that while both the Yano­mamo and Wao­rani’s ag­gres­siveness is for re­venge, the Yano­mamo’s war­fare cy­cles have peace­ful in­ter­ludes where war­riors can reap the ben­e­fits and ac­crue wives and chil­dren. The Wao­rani men do not in­cor­po­rate peace­ful in­ter­ludes be­tween their ag­gres­sive en­deav­ors and will even in­i­ti­ate an ac­tion based on some­thing that oc­curred in their grand­par­en­t’s genera­t­ion. In gen­er­al, the Wao­rani goal was to elim­i­nate the oth­er side. 

Anoth­er dif­ference be­tween the Yanomamo and the Wao­rani is that even with chron­ic war­fare, the Yanomamo popula­t­ion had grown over the two cen­turies be­fore Chag­non’s in­ves­ti­ga­t­ion. The Wao­rani lit­er­ally seemed to be on the way to “killing them­selves off” at the time of their disco­very by out­siders, ac­cord­ing to the re­search­ers.

* * *

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Some anthropologists have considered aggressive, vengeful behavior among certain South American tribesmen as a way for them to obtain more wives and children. But anthropologists working in Ecuador among the Waorani people have found that sometimes the macho guy doesn’t do better. In 1988, the U.S. anthropologist Napoleon Chagnon “published evidence that among the famously warlike Yanomamo of Venezuela, men who had participated in a homicide had significantly more wives and children than their less warlike brethren,” said anthropologist Stephen Beckerman of Penn State University. Yet “our research among the Waorani indicates that more aggressive warriors have lower indices of reproductive success than less warlike men.” Chagnon took considerable criticism for what opponents considered his suggestion that violence was a natural, ancestral human way of life. But Beckerman didn’t contest Chagnon’s findings; he instead argued that the Yanomamo and Waorani have two very different situations. The Waorani are rainforest manioc horticulturalists and foragers. When the first peaceful contact occurred in 1958, they numbered about 500 people living in an area the size of New Jersey between the Napo and Curaray rivers in the Amazon basin east of the Andes. Their abundant resources often attracted outsiders, who were promptly killed if found. Warfare and murder were common among the Waorani, who are known to be more warlike than the Yanomamo, according to Beckerman and colleagues. The Waorani practiced their violence on each other as well as on outsiders. Eventually, over a period of 14 years, missionaries pacified the Waorani. Aggressive warfare and raiding are now almost gone. “In light of the documented abundance of wild resources, resource limitation cannot be considered the cause of warfare among the Waorani,” said Beckerman. Beckerman and colleagues looked at how a man’s participation in raiding correlates with his survivorship and that of his wives, the number of his wives and the number of children he produced and their survivorship. The researchers interviewed men in 23 settlements. They interviewed any man old enough to have experienced warfare before the pacification that could be found and who agreed to the interview. The researchers collected Waorani men’s genealogies, reproductive history, narrative personal life history and warfare history. The raiding database contained 95 men. Beckerman and his colleagues report their research in this week’s edition of the Proceedings of the National Academy of Science online. “Our sample of warriors includes both living and dead men,” said Beckerman. “We ranked aggression by the number of raids they participated in. Our analysis is free of the problem caused by the inherent correlation of the warrior’s age with both participation in raids and reproductive success.” The researchers found that more aggressive men do not acquire more wives than milder men. They do not have more children and their wives and children do not survive longer. In fact, warlike men have fewer children who survive to reproductive age. Why do these results differ from Chagnon’s and why are Waorani men so bellicose when there appears to be no benefit? The researchers suggest that while both the Yanomamo and Waorani’s aggressiveness is for revenge, the Yanomamo’s warfare cycles have peaceful interludes where warriors can reap the benefits and accrue wives and children. The Waorani men do not incorporate peaceful interludes between their aggressive endeavors and will even initiate an action based on something that occurred in their grandparent’s generation. In general, the Waorani goal was to eliminate the other side. Another difference between the Yanomamo and the Waorani is that even with chronic warfare, the Yanomamo population had grown over the two centuries before Chagnon’s investigation. The Waorani literally seemed to be on the way to “killing themselves off” at the time of their discovery by outsiders, according to the researchers.