fei75766_ch15_463-494.indd 481  02/24/20 10:48 AM
Chapter 15    Buss: Evolutionary Theory of Personality481
these questions inaliving society thatcomes closer toearly ancestral conditions than
modern industrialized cultures. Onesuchculture isasmall-subsistence society ofthe
Amazon inSouth America known astheTsimane’. They livein90villages thatrange 
insizefrom 50to500people. Education isavailable andyetrelatively fewTsimane’ 
havecompleted high-school andonly25%ofadults canread. Moreover, infant/child 
mortality rate(diebefore age5)is20%. 
Toaddress questions ofhowpersonality might berelated toproblems offitness 
(survival andreproductive success), Gurven andcolleagues (2014) asked thefollow -
ingquestions intheresearch withtheTsimane’:
 1. Is personality related to reproductive success?
 2. Are there costs of being extraverted, open, prosocial, industrious, and not anxious?
 3. Is personality related to and does it impact fitness-related activities (that is, time 
spent in childcare, socializing, and working)?
Toexamine thefirstquestion, Gurven andcolleagues (2014) firstmeasured 
reproductive success bynumber ofchildren (fertility), number ofsurviving children, 
andageofmother/father when theyhadtheirfirstchild. They alsodeveloped a
BigFivemeasure ofpersonality fortheTsimane’ intheirnative language thatmea-
sured Openness, Conscientiousness, Agreeableness, Extraversion, andNeuroticism 
(OCEAN). Previous research hadshown thatthese fivedimensions canbefurther 
simplified intheTsimane’ toProsociality (helping andcooperating withothers) and
Industriousness (work ethic anddependability). Theanswer tothefirstquestion of
whether personality related toreproductive success isnoforwomen andyesformen. 
After controlling forage,schooling, mean withhighest levels ofExtraversion, Open -
ness, andConscientiousness, andlowest levels ofNeuroticsm hadhigher rates of
fertility (more children) andmore surviving children. Agethatthemenfirstbecame 
fathers wasunrelated topersonality. These results alsosupport thegeneral finding 
thatpersonality traits aresexually selected traits inhumans andnonhuman animals  
(Schuett, Tregenza, &Dall, 2010).
Toanswer thesecond question—Are there costs ofhighExtraversion, Open -
ness, Prosociality, Industriousness, andlowNeuroticism?—Gurven andcolleagues 
measured costs interms ofhealth andsocial conflict. Health costs weremeasured by
body-mass index (BMI), andvarious blood testsmeasures ofstress (cortisol), inflam -
mation, andinfection. They found asmall health costeffect (some elevated mea-
sures ofinfection) formenwithhighIndustriousness, butingeneral menwhowere
extraverted, open, andprosocial hadbetter health thanmenwhowerelowonthese 
personality traits. They measured social conflict bytallying number oftimes allothers 
interviewed inthatvillage saidthatperson wasinvolved inconflict. Results forsocial 
conflicts showed thatmenwhoweremore extraverted andopen hadmore social 
conflicts withpeople intheirvillage. Ironically, prosocial menalsohadmore conflicts 
andmore industrious menhadfewer.
Finally, thethird question concerned therelationship between personality and
fitness-related activities, asmeasured bytimespent withchildren, socializing, andat
work. Results arepresented inTable 15.3. Ingeneral, personality ismore related to
fitness-related activities inmenthaninwomen. Unexpectedly, lessagreeable women 
spend more timewithchildren thanmore agreeable women. Thefitness-related activ-
ityofsocializing ismore strongly related topersonality thanother fitness-related Final PDF to printer