The Evolution of Reciprocal Sharing

Jim Moore

GenetIcal models of the e\olutlon of reciprocal altrmsm

was distinct from cooperation. mutuahsm. or nepotismI

have ddllcultv explammg the mitral estabhshment of an

altrmst gene in a selfish deme Though potential mech-

anisms have been suggested. there IS an alternatl\e

much “altrmstlc” behatlor ma\ m fact be pureI\ selfish

m orlgm and consequentI) reclprocit\ need not be m-

*oked to protide a selectwe benefit to the actor Shanng

and hr$mg are fundamentalI\ different behavior cate-

genes and should not be confused Patterns of resource

shanng m chimpanzees correspond to predictions made

b\ a sellish model but not to those of a reciprocal altru-

1sm model, and man) observations of human gift ex- change are consistent with the selfish. but not the al-

truistic. model This suggests that presumed hominid

meat exchange mav have been the result of competition

not altnusm or eben cooperation. and that e\olutlonar\

models of “altruistic” behavior should be treated with

caution

hey ifords 4ltrwm Reclprocu) Chlmpanree Hom-

mid

INTRODl’CTION

43 emphavzed b\ M llson I 1975 p 3) true al-

trul>m 15 blologtcall~ parado\lcal m that dn) ge-

nettc InchnatIon towards \ell-sacnlice mu5t cl151

m >p~ttt of that \er\ bacrlfice Trl\er\ addre:s\ed

the problem of Jtrul5m hetbern unrelated In-

dlvtdual5 In ;\ landmark paper I 1971) He rrrgurd

that \uch 4trwm 15 nd\antageou, to 11% prx-

tlttoner If directed onI1 toHard those Indl\~duA\

it ho UIII reclprocdte gt\en the right co\t-ben-

efit ratto over ttmr each member of a reclp-

rocal relatlonshtp will do better than b) acting

alone 45 ConcelLed bv Tnbers reClprOCdl al-

truism 15 mo51 Itkel\ to evolve tn species \ilth

long It\e> good memorte5 and ~IKOUS popu-

lations tthosr tn H htch tno Indt\tduals ~111 meet

many times and remember each other 3 pa51 be-

ha\ Ior 1 There are at lea51 1v.o dtfficultles mtth Trek-

er5 formulatton First. the mttlal altruist In a

populatton 15 a lone altrul>t \ttthout rectprocltl

the tndl\ldudl IS at a dt>ad\antage 50 the trait

n111 not spread I Wd5on 1975 pp IX-121 I Thts

mtttal dtstdkantage applw equalI> to all altruts-

IIC beha\ Ior regardless of \pecte\ and ha> been

addressed a5 a populatton genetics problem tv

vseral author5 tWll5on 1977 Boorman and

Lebttt I980 Fagen 1980 Auelrod and Hamilton

1981 I all of Hhom hake relied on arguments that

\ome form of drift hm or group Aectton 15 nec-

e55ar) to establish the altru151 gene tn a popu-

lation For example failure of ktn-recognttlon

>\ 51ems due IO genetic or demographlc change\

could lead to km-selected dltrul5m becoming ac-

cldentall) generaltrcld to nonkln a 5e:cond se1 ol

adaptations then arlstng IO enlorce dtscnmln+

[Ion agaln5t nonkln nonrecIprocator I Alelrod

and Hamtlton 19811 Second among human3 It

13 b\ no mean5 clear that the rectprocal ex-

changes to which Trt\er, refers are altruistic

in an) cen5e of the word tSahltn\ 19761 Contraq

IO what 14 often assumed much human rectp-

rocal gift-gll mg IS charactertred not bq altrutsm

a5 ~\ct commonI\ use the term but lx prev

tatton \\hrch are In theor) Loluntari disin-

teresled and spontaneous hut are in tact oblig-

ator) and interested The form u\uallq Liken IS

that ol the gift grnerou~l\ ottered bur the A-

cornpan) tng beha\ tor I\ formal pretence and \o-

CIA dcceptton Hhlle the transxtlon ttwlf 15

6

DEFINITIONS

Author\ dl\cu\\lnp human .tl1rul\m h.l\e tended

to Jdopt term\ Iron1 ctjmmcw u\Jge \\ rthout

cle.~rl\ dellrnng them \~orJ~ \uch J\ nltru- i\m helping cooperJtion .md \hJr-

w JII hJ\e \llghtl\ dlfterent cc~nnotJtton\ Jnd

II IX Important to dl5tlngul\h Jmong them For

e\Jmplt: Jlthough Trl\w ~\~IIcII~\ e\cludd

cooperJtwn lco~qwrJtl\c huntIngI In hi\ trtt.lt-

men1 ot reciproL,ll ~ltruiwl \wlrnd and HJm- 11ton t~tld J recent pdprr The e\alutlon ()I CO- 0perJtion Jnd cnnslder ~onperJtlon Jltruww

Jnd re\rr.nnt during competition 10 be reIdted

phenonww e~pl~c‘.~ble by either bin wlc‘cllon or

reclprl~cJtlLm theor\ f \wl~od Jnd HJmllton

19x1 I In the preceding p~“JgrJph\ I hJ\e uwd

thr: term Jllrul\m a\ Trl\er\ Jnd other, hJ\e ~14 J 5rngle conceptual tr,ut For m.ln\ purpo\e\

ho\\e\el II I\ ImportAnt IO m.thr &I dl\tlnc1lon

het\rern helping and 5harlng

ing penrrdll) cannot le g J baboon eliciting help In 3 fight Gould onI1 double he problem\

h\ JttJching a noncomplidnl potential all) and

threat5 Irom a drwnnlng ptrwn mai not lx \er\

etfecll\el

-\/frrr~c/rc bt#rcr~ w I\ her? &lined a) behJ\- ior th.11 benttlit~ an UnrelJted indt\ 1dual1~1 \\ hlle

being detrtmrnlsl Ico\t benelltt to the actor

In the short term Art\ Jddtttonnl long-ttirm ben-

t‘ltt\ to the actor ~\thtch might rr\s,tl the C-B

tnequ.lltt\ I are conttnpent on bubwquttnt beha\ - wr tw the rttctptrnt tar other41 wc‘r \shtch the

JCtl)r has no cixItrol coot .HId hen~til .1re

Sl/~Vf I( 11)1 Jnd L,vrc lClll/ hlutusl bent IIt .m J c’\trrme wit-intri~~t can t-v combined to produ,e niutualiwi Ic‘ g inseLI pollination 0I

Ilo\rer\r In \I hlch both pJrtw berefit nsJrl\ \I-

mJltJnWU5l\ tram <aCh tntera~tton M hen the

re\rdrdb Jre tmmttdto tar both JchWl ch<dter\

LJn bc punl5hed \impl\ b\ termtndting 1he in-

terJctwn rln the case nl ~lmultrrneou~ benelit 1 or

b\ ph\\~cal attaLL II the che.ltrr trw IL) Ie~\e

\\lthout rtclprocstlng IL< hen ben&it~ Jr-s w-

qurntlJl irrth ;I short Intc‘r\Jll Hwe\rr ,I\ the

intsr\al bet\iwn rs\s.Ird\ lncreJ\c‘b 11 lwomr\ eawr lor one tndt\ I~~UJI 11) c hrdl at the e\ptlne

ol the other cla>vL;Ll \&Ltlon (a\ortng sAfi\h-

net\ should thpn decouple mUtUJl hen&t Irnm wll-interr~t II the Intel\dl het\\een InlerdLllun~

IS \er\ long-e g It J IrlL’nd \J\e\ nie tram

drwning Jnd no1 unlil ren Iedr\ lJter JrC the

t~hlc\ turned-there I\ I~ttl~: to \IO~ the beneti- LlJr\---me-~rolh \\Jlking aiiJ\ Jnd It I\ ditfi,ull

10 blOlofl~Jll\ e\plain m\ LkLlw)n to rE’CIpr1)

<are It on the other h.lnd m\ tlwnd \r~wld l\lbrnehw I benefit ImmellJ1el\ tram m\ >JI\J

IilvI there 15 no allrui~m and nc) pJrJdO\ L~rp- ICJII\ there must be wntt‘ length ot time helo\\

\rhlch benefits Are prompt Jnd mutualiw Jde

quote lo explain brhJ\ kw (the >hort Isrm 1 .md aho\ c: u hlc h the potenttJl lor cheating I\ w greJt

The EL olut~on OI Reciprocal Sharing 7

19821 No global rank >\,tern 13 lmphcd b\

the finding of a po\ltl\e correl~tlon bet\\een bo-

clal rank or prestige and RS among monkc\s

apes and humans of both se\e\ I Hau5ldter 1975

Russ .md Goodall 1977 Gomlla 1975 Hat-tune

1976 Chagnon 1979 Iron\ lY7Y Deu sbur\

IVXZI

FOOD SHARING B\ CHlhlP4NZEES AND Hl’hlANS

Chlmpdnrees u ho hake meat \!III share It filth

others u ho beg for it I Lam Ick-Goodall I968 Te-

Iekl lY73L albeit sometIme\ reluctantl) lNl\hldd

et al 19791 The >harlng ot plant foods I\ Ie\f

common and occurs pnmarll\ \\lthln lamI-

Iw-of 457 transfer5 ol banana\ ob\er\ed A

Gombr 391 18hCc1 \\ere bet\\ern mother and otf-

spring and 47 ( IO?) \\ere tram adult male:\ to

unrelated adult females I hlcGre\\ 1975) Food

shanng among relatr\e> clearI\ doe5 not require

a rrclproctt\ theor) the dlscu\\lon here ii111

therefore be restrtctcd to con\umptlon ol \cr-

tebrste pre\ (often dssumed to be a ke\ tdctor

tn human e\ olutlon-e g SchAler and Len thcr

1969)

that selt-mtero\t should wm (the long

term I nece\sttatmg an r\plnnatlon tor reel-

proLIt\ \uch as TrlLrrs or I offer Rigorous Jet-

mltlons of short term and long term need

to be developed but are not nece\>ari for un-

derstsndmg or te,tmg the model presented here

Tnver3 listed fi\r t\pe> of human beha\lor

that he con4rred AtrulstlC I I I cdrmg lor sick

dlsdbled or otheru l>e Incompetent mdl\ Idual>

(21 \harmg kno\\lrdge 13) toad sharing (41 \har-

mg Implements and 15, helping In time, of dnn-

ger Caring for Incompetent Indl\ ~duals Include,

aspects ol shanng and of helpmg a> defined

abate Sharing of knom ledge doe5 not ed,rl) fit

either catrgor) Homeber mo%t practlLal knot{ I-

edge Ldnnot be Implemented \rlthout \harmp

it among all interested ob\er\ers c g among

the ‘Kung San of the Kalaharl there I\ ier\ little

actike mstructlon ot children-the) simpl\

watch adults and practice M hat the) \cte (Draper

1976 \ce al>o Whltmg and Whltmp I975 p lx01

If mdlvlduals Share knouledge pa>\l\cl\ II I\

unneces\ar\ to tnbokr altruism ol an) sort to

eiplam the phenomenon MLGren I 1977) make\

a slmllar dt\tmctlon betaren ob>er\atlonal

learning and Inbtructton m chlmpanrcrs

In this article I use the spccllic term, ~r&rrrp

and shrrnq \\ hen it IS neces+dr) to dlrtlngulrh

them othcr\%~se both are Included m the general

term nlrrrtrsm Cooperatlon doe\ not tit the ba\lc

condttlon of altruism m that all the actors deme

lmmedlate benefits from the dLt of cooperation

classlcal I mdtvldual I sclectlon I\ sufliclent to ac-

count for the e\olutlon of cooperattve behablor

tTmers 1971 I Except uhere specified coop-

eration IS not conslderrd m this paper

Donr~ntrnc (J and prrcrrgr are con\ldered to be

two aspects of the 5ame phenomenon analogous

to the dtstmctlon made b) Maslo\t 11917) be-

t\heen ’ face-to-face and cultural domi-

nance Both dominance and prestige are usualI\

associated wtth access to rr5ource5 that can af-

fect reproductive success tRS1 and mdt\ Idual<

are expected to behave so as to maxlmlze their

status on one or both of these axes The cor-

relation between dommance tor pre:stlge) and RS

need not be perfect tar selectton to favor attn-

butes that contrtbute to dominant Status hke-

UIS~ domtnancc rankings constructed nlth ref-

erence to dtfferent behavioral domains te g

acces\ to plant food and access to mate\) need

not correlate perfectI\ lor domtnancr IO be a

meaningful concept Isee. for example Smuts

Chimpanzee predation and meat \hartng ha\

been dlrcussed extensl\el) and de\cnptlon\ can

be tound m Lawlck-Goodall I 19681 Telekl

(19731 Nlshtda et al I 19791 Kananaka tlYX21

and elsewhere The \ahent points for thl, JIS-

cushion are as foIloHs

SPA Ajjrrencrs-Hunting and meat Len-

sumptlon are pnmartlq male actnltles (above au-

thors also Wrangham 1975 McGrcn 1979 but

note exceptions do occur-e g Moms and

Goodall 19771 Telekl found that female\ recel\e

meat roughlq as often as do males but the) tend

to get much smaller porttons after most of the

ktll has been consumed Famlllal and perhaps

hormonal status pIa\ a part m females’ meat con-

sumption Just IUO females. Flo and her daugh-

ter F~fi account for oker half of Telekl’s obser-

bations of female partlctpatlon tn takmg

requesting mteractlons and the onI1 female he

sah receivrng a fair portion was GI~I who

was m r\trous at the time GI~I IS an Infertile

posslblv adrogemzed female tR13s and Goodall

1977) so II IS not clear whether her masculmtt)

or her estrous contnbuted to thts success Be-

cause meat shanng IS a prcdommantlq male ac-

ttbtty m chimpanzees. the model presented here

could be aoohed to ’ innate sex dtfferences m . .

human reciprocal e:uchange or rn the dI\Irlhutlon

of hln-dlreLrrd bersu\ nonkln dltrul\rn IF

dt~\ 510 /t cltll~w th es t’\f\f Comempornr) \ie~I-

ern cuhure rend> 10 dl~cnmlna~e agam\r \\om-

en 5 particlpalion in pubilL --clfecti\el~

nonhm-affair, and con\rquemlI drmon~trd-

tlon of an) hiporhrllcal Innare \ZY dlttrrences

Ias dislmcl from cultural t 13 probdbl\ impo5,lblr

and 14 not attempred here The model presented

I\ based on genellc kelfishness and Jn J\socla-

tion bet\tern >talus dnd reproduLf1on in pnn-

ctple it applier equal11 uell 10 fem.rle\ and male5

Igee Hrdb 1981 tor a re\reu of Lompetltron

among temale pnmatesl

Prrdclrrott cud ~lrc c otrrrol rrh~ -During

rhe tirsl mornen tollo\rmg a capture an\ In-

d~~ldual pre\rnt can grab a piece In fact \orne

preb are killed IncIdentall) b\ dlsmrmbrrmenl

ITrlekl 1973, \er\ rhortt\ though the holder

of meaf becomes 11s po,sc,sor and \natchlng

pieces 15 more or lrcs replaced h\ \ariou3 torm5

of begging Dominance <1;11115 IS nor totall\ QI)-

pendrd and \er\ IOH-ranbmg Indl\lduat\ do tend

1o to\e IheIr hrll\ bur rn general the holder a\-

surncb m haI Telrkl terms the control role and

other\\ use domlnonr rndl\ ~dunls u rtl respect Ihe

holder s o~nsrshrp The basic plcrure I\ one ot

clusters ot three 10 four adult, Around each

holder ot a major share begging or tr) lng ho run-

dggres\lvel) I take piece> of the prel Fallen

scraps dre eaten b\ mdlvlduals too loam-ranhlng

10 Jam the clulrers ipnmarll) \ubadult\ and

home female\, dnd rhe entire kill IS consumed In

from I S KI 9 hours (Telekl 19721

While this beha\~or has been Interpreted as

,m example of reciprocal altruism ie g Wilson

1975 p 128 McGren 19791 branghdm 119751

has suggcbted that rhe pnmark morr\atlon of rhe

nmmal posscssmg the meal rndl slmpl\ he relf-

protectIon Because chimps habe a relatIveI)

open dominance hlerarch) (ban Law Ich-Goodall

196X. Tetekl 1973, rhe po\sosor of the meal

I Ego) 15 potentIalI\ \ utnerablr ho artack b\ Oth-

ers H ho desire a share Meal IS an rasd\ carned

(and shielded) resource so rhe prob.ibilrt) ot

Other gaming possessron of the meat uuh a cas-

ual threat IS IOU whereas the cost ofa real altack

IS potentIalI) high te g energ) loss rlrk of in-

Jur)) Note that if Other Judges this potential

cost 10 be less than the benetir Ego IS slltt at

nsk furthermore Just the need to guard against

a possible attack by Other IS a problem for Ego

the resource ma) be detendabte bur there I\ no

opporrunui lo eat If It ma\ therefore be In Ego \

Immediate mleresl IO g~\e up [u/r/ ot the hill

trading II tor the opportunui 10 eal \thdt 13 letI

m rrlatrle peace rtor J IheorctlLdl di>cus5ran ot

Ihe\e I\QI~S see hla~nard Smith and Pdrher

IY7hl

Human >hannp and ekchanpe ImerJclron\

occur m three more or Ies> dlstlncl cla\\e\--re-

clprocal e\chdnge Ithe focu\ of hlau>s c anall\l\

and Triter\ \ and rn\ model\, bdrler or >ale dnd

simple nonreciprocal pi\ rng Barter need5 no t?\ - otutiondr\ explandrion except perhapc 11)

note rhac b\ ,ub>tltutlng ,hon-term tor long-

term balancing ot interactron, 11 3~1s 10 reduce

the opportunlt) for \elti<h Lheatmg on reclprocdl

exchanges Human toad >harmg turrl\ the eJr-

Iie5t form ot nonreciprocal 1d5 \!elln\ reciprocal1

grump ha\ been e\len\l\eI\ re\ie\red b\ Feln-

man I lY791 who conclude, Ihat the \ ~51 rndJorl1)

of \uch Interactions occur bet\\een relarcd In-

di\idudl\ and so fit the predlcrlon\ ot hln \etec-

lion The remdmlnp mterdctlon\-gl\ rng ~a non-

relall\e, \\rth benstir\ 10 Ihe lmtlnl aItruI\t

dpparentll depending k>,n long-rerm rrclprocd-

IIOn-dre the focus of throne\ ot rrciprocdt AI-

lrul\rn In Lonfrast IO Intratamdlal \harlng ldnd

aI50 10 Ihe balls of Tn\cr\ 5 mode11 \uc h Inter-

actions are often hostlIe and charscterlzed hi

lensIon and deception tMau>\ 1967 Sahlln\

tY6S 19761 Moreover as I) apparenlti the c;l\e

ullh chimpanzees among human3 the \hanng of

resources is socialI\ enforced For a Hadza

hunter 10 fall 10 3hare a large ammat ulth other

members of the camp m which he 13 II\ Ing I\ to

m\ltr vIolen retnbutlon I Woodburn t 972

see also Sahhns 1965 p 1661 Lee I 19731 poinr\

auf that homicide rates among the ‘Kung in-

crea5r \slth group \lze larger groups breaking

apan over d~spules about the dl<tnbutlon ot

tood Woodbum (19721 also ,tafe> thar Incred\rs

in group size can cause trouble The more SUL-

cessful hunters In partlculdr UIII be ternpled 10

depart presumabl\ belcausr the\ feel exploIted

b\ rncreasmg numhrrs of stachers Man\ gath-

erer-hunter soclellcs have elaborate rule\ go\-

ermng the dlstnbutlon of meat honeler Ihese

rules are often onI1 poorI\ self-enforced and

when opportumtles to conceal meat trom people

oulslde the farnil) an5e the\ are often taken

it: g Turnbutl 1961 pp 94-108 DeVore per-

sonal communication)

The Evolution of Reciprocal Shanng

THE EVOLUTION OF RECIPROCAL SHARING

If Ego (an mtelllgent chimp) risks a se\err bent-

mg whenever he or she catches somethmg edible

and tnes to keep It he or she u III soon learn not

to be stmgy Ego should learn qulcklv and 11111

be better off learnmg not to be stmgk rather than

not to hunt It IS these qualmes-a propenslt\

to learn the right sort of thmg and to learn It

quIckI) -that ma) have been favored b\ natural

selection (Hamburg 19631 Because of the threat

of enforcement. the propenslt\ to learn to share

with non-relatives may have evolved among

chimps and humans pure11 through mdlvldual

selection The chimp evidence IS especIalI) ,lg-

mficant because chimps possess all SIY of the

charactenstlc5 Tnvers con5lder5 favorable lor

the evolution of reciprocal altrulsm and \et meat

sharmg IS the onI1 altruism 5een outside the

contexts of

of their

et

of human

15 based on the

a chimplike social orgamzatlon rcf Revnolds

1966. McGrew 1979) uho were capable of

( polItIcal I stra-

tegies to achieve their goals (Walker Leonard

1979. Curtm 1981) Based on studies of chlm-

panzees. three propositions about these ances-

tor\ form the basl5 of the model

I They had a relatlbely open dominance hoer-

archy. bet male5 at lea\t mere hIghI mo-

111 ated to achleb e high rank I see van LaH Ick-

Goodall 1968, pp 212-214 R15s and Goodall

1977) When rank IS correlated NIth RS m-

dwlduals are expected to behave so as to

maximize rank eben uhen competltlon for

tmmedtate resources 15 not an Issue le de

Waal Hoekstra 19801 In long

positIon reward but rn 5hot-t

run. position Itself IS the reuard 1 Wash-

and 1968 p 4731 a

for high It5elf ma) exist to for-

relatlonshlps so that serious fighting

over resource5 tmcludmg matr5) IS abolded

l5ee Wilson 1975 chap 131 high rank ma\

also confer relative reproductive adiantage5

9

IIU spiteful behavior ISIlk 1980) and endo-

crmological 5treS5 effect5 on subordmstes

[Dunbar and Dunbar 1977 Kelerne 19811

The) exhIbIted begg:ng beha\lor that na5

probabl) as m chimps performed mo5t often

b) an Infant toHard IIS mother tMcGret\r

1975 Silk 1978) Such beggmg wal b\ nature

submlssl\e m that It signaled I Uant tihal

1 ou ha\ e but am l no% unable lo tahr II

lou’

I \~ould

be

thdt

m transltlon from adulthood m particular stwe to achwe status These In- do\ [duals te\t more

cost

to t

Other

(o&SF)

/ /

/ /

/ /

/

t Time I,

The two ordinate scales

Benefit

t to

Ego (EBs)

are not equivalent.

The E\olutwn ol Rrclprocal Shartng II

ttng the nxldent pa>\ due\ not Iowe the IYWC islth higher-ranking Other5 H ho LouId cheat by

but In ellect turther relnlorce> Ego \ temporJr\ euploltlnp Ego The present model on the other

gJm m >LIIU> Other rndl\ duals ha\e >ren Other hand hold, that II ,harmg I\ a mean5 ot avordlng

beg from Ego to mJmtdln po5ltwn In the hwr- dttxk and ot gdlnlng SOLIdI >talu> 11 should be

.Irch\ Other should .r\oij the AppeJrJnLe 01 prelcrentl~ll~ dlrccted tward those \i ho are

Lieakenlng Thl\ line 01 re~wninp 15 demon- mo5l Ilkrl~ lo attack and tho5e M ho hJ\e higher

>tratrd In the phenomenon ot redu-ected &?grr5- 5tdtu, to trade

\lon In M hlch the lowr of a light attack\ a lwer- Ewmtntnp tndt\tduJ wcce>\ rate5 ol eight

ranhlnp b\>t,mdttr dsmon>trdttng 10 all other m- Jult mdle Gombe chtmpanzce\ I+ rnngham

JI\IJuAI> that hi4 or her competltl\e ab111t\ ,nd tl97Ct Iound that Jllhough there Hc‘re no \I\-

rJnb ha\e no1 in tact Lhdnped (Popp and tematic dtf~ercncr~ among male> in r-ale, nl prei

De\nre 19’1 p 611 capture reldttke 5uco35 of ohtaininf meat and

Other ma\ hwe\er choo,c to rectpro- reldtt\e age \\ere po\ili~el) correlated ISpear-

fate-Jt some time in the nex future Other ma\ mdn t = 0x1 p 0 01 I N’ranghnm 5ugge515 obtain J slmlldr valuable rewurc~ and IJsWm- that tht\ correlatton 13 due to the louer rrpro-

mg Other can no more monopoltze II than could

Ego) ii111 \\ant Ego to knw about II Jnd lo beg lor II Ego \\III be on11 tw hJpp\ lo do w JY

long ~4 EBn EC\ Predtctrd then tn chtnt-

panZee\ 15 pO5ltl\e WhXtlOn lgenetlL w~cIJ~ Or ontogenctl~ I lor IrJlt) ~14w~i~te~ \\ lth I J?$!re\ \i\el >harlng JnJ ri%lprlxJtlng ld\W?l\t?~\ 10

rw4tablt\h \I~IU\I

In humrw the ho\ttltt\ of potlatch-t\pe r+

ctproctt\ can he wen tn thl> larger conte\t Ego

recJllmg Other > eJrller wbrnl\>l\e heh.l\ lor

\r~ll be motl\a~ed to rectprocate .md w the t-e-

Iattotwhtp IS begun Ego 5 dwre to rrclproc~~te

\i III be matchrtd b\ Other 5 remlndmg Ego ot the

debt to publ~~li empha\lze the current >LIIU~

relatlonshlp the demand lor repa)mcnt mJ\

ortglnall\ hake been Implwtl\ or r\plrc~tl\ a5-

wLlated with the hope that the debt \~oulJ re-

m,un If the debt relatton>htp ttwlt hcLomet\ a

ductlve value of old Indl\lduals the) nsk less.

In term\ ol potentlnl offsprmg lor rxh unit of

rewurce gained and nre therelore more ~\~lllnp

to at~d~h In tact the t\\o olde5t male\ iMIke

Jnd Hugo1 \!ere ln\ol\ed in YU’; ot obwr\ed

JttAhs wer meat 1 v = 201 Because of 5oc1rll rank change5 .lmong the

male\ dunng the study period Wrangham \+a5

unable to ~tatlstlcall\ analvze the relatton5hlp

hetheen ~LCCI\ at obtalnlng meat and social

ranh The three male5 \i ho held alpha ranh dur-

mg L+‘mnphnm 5 \rud) rhllhe Flgan and Hum-

phrr\ I ranhrd 2 1 and 5 ln wxe51 nt getting mrdt the fourth-ranked NCI> Fnben brother ot

Ftgan and the mo\t su~~e~~ful male Hugo \{a>

old and lo\\ rJnktng SImIlarI) Nlshlda I 10701

Telrhl I 19731 Jnd Kawanaka II9811 all conclude

that high-ranking males are more Itkrl\ to obtain

meat than are lwer ranking one\ though hter-

mator Impetus Iward> \harlng then II lollw\ arch14 relatton,htp\ are great11 relawd rel.ttt\c

that Jttlicultl 01 repJ\ ment not UIIIIIL \~III be 11~ other \ltuatwn4 Thu5 among chimpanzee

3 primat-\ factor in wlecltng a gill tone 4u5pect5 male\ older and/or higher-ranking tndt\ 1dual5

Chwtmas gills Jre wmrtlme> chown lor this are In fact more Itkel\ to retcet\c: \hare:s ol meat

redwnl -I\ Sahltn, ( 19761 hd5 potnled out po- de5pttr the lower probdblllt~ that the\ 1~111 re-

tlatch kula big men and other formal e\-

change \l >tem> are better undewtood In thl5 wl-

Vi\h light than the) are J*l e\antple> of Jltrui3nt

TEST OF THE MODEL

if ,hJnng 15 promoted b\ the e\pectJtlOn ot tu- turr rectprocatton and mutual henelit there it111

be a trndrnc\ 11) be \tlngi touard old mJI\Idual\

1s ho mai die More reslproc~tmp rTrl\er, IY’I I Regarding 51~1~3 Trl\er\ mahe< no prediction

J3 to chwce ot .i rectprocJl shartng partner bul

II wem\ Ithel\ that Ego >hould ~LOI~ shartng

ciprocate

The dtstnhutton 01 meat 3hartng the be\t-

knwn rumple ot reciprocal JltrUI,m in chimpanzee, I\ e\pldlneci b\ tht\ model hut not

b) that ol Trticrs

SH \RING AND RECIPROCAL ALTRl’lSM

HumJn \hanng helping and cooperating are be-

hai w,rA~ slmllar and are emottonall) tntercon-

netted II I\ pos\lble that cla551c 4fish wlec-

tton lor relctproctt\ JnJ ag!.gre\\l\t‘ \hartng itas

re\potwble tar e\Mll>hmg emotion\ that lorm

I2 Jim hloorr

SllhlhI-\R’I

thJl fiw JpeS mwing rnto .I hunting Iiled\lr

wch meJt status r\chsnge, pla\sd Jn Important

part In Jetermmmg an Indl\~duJl , ranh v.tthm

the wc1a1 hlerxLh\ and hence lnllucnced her or

hl\ RS

They model 01 the wgln\ ol rtxlprocal >harlnf

pro\ lde\ the loohed-for reproductl\e ~d\antJge

JccrUlng to an JltrUbt in J nonaltrulbl popu

IJtton Selertlnn tar tral1~ JYWCIJ~~~ \tlth thr:

Jblllt\ 10 optlmrlll\ IJk? ad\JntJ@ Ol wch rt’

ClproLJI ewhange I\ Ilhel~ to hJ\e Inllo\~rd Jnd

rhe C‘rlll~Jl mcredw ol these \rJltY in the pty?u

l.ltlon mJ\ h3\e alln\\ed true reclprocJl tr/fr/rr\~r

to become e>tahll\hed emorIon\ r\olied ln Lvw

cantext prcadnptlng lndl\~duA\ to t,lhe Jd

\Jntage l)f ne\! pl~~~lbi~i~it‘\ flw cwpe‘ratilm JnJ

helping as \rell a4 shJrlng c~w~clou~ manlpu-

lntlon 01 these emorIon\ awld then lorm the

bJ\I) ot J generJllZed Or \UclctJl rc’clprlxlt\

rthlL wch a> I\ nw Inund In human\ tTrl\rr4

1971 I and pos+l) odont0~ett‘ <&IceJIb IC on

nor and Nnrrlb 19821 \ltern.ltl\el\ II I\ irorth

notint: IhJt humJn> Jnd ~&wIncetr~ ma\ share

Jnother untque Ienturc-the ablllt\ 10 lnlllct ln

tur\ or &Jth on LonywclliL\ \iIthout \iJrnlng

Jnd \\ Ith 111tle IWM clrc,fc rl\h 1 human\ \i lth JI\-

[J&e \r~Jpon~ wch J\ by\\ \ er: blacDonJIJ JY-C Lee IY% LhJp I\ ~~dontocett‘\ b\ high-

lnten,lt! wnlc pul\rt\ Norrl\ Jnd hlohl IYXI I%? R C‘onnor pt‘rwnJl c~w~munl~dlwnl LII

tie InfOrmJtlOn I\ CI\ JIIJ~I~ I c‘t on blphln \ uw

01 high-lntcn>lt\ ,ound Jq .I tool l!eJpon Jnd

thl\ point mu51 be tre,ltCd JX sprculJti\e tot- no\r

lt trw it \\ould wgg~3 IhJt Jpparentlb .~~trui~ti~

helping In both group\ ma\ reprewnt J ~uIturC~ll\

enforced et\tension (>I nepotl\m \harlng nrl\lng

lrom \Jnctlon\ JgJln\l non,lllrul~tr rrlther th.ln

.ld\.mtJge> xauinp 1~ JItrui\ts Icl gewr.ll-

ized ,Iltrut~m Trl\<rl 19-I 1

The E\olutton of Reciprocal Sharing 13

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