Gift games among Saami pastoralists show group membership can be more

important than genetic kinship

Matthew G. ThomasBård-Jørgen Bårdsen

Marius Warg NæssRuth Mace

Cooperative herding- sharing, defending, loaning, exchanging

- lowest cost strategy

- pooling risk

- presence of relatives associated with increased herd size

Cooperation influenced by mix of genetic (kin selection)and social factors (reciprocity)

Aktipis et al. 2011; Apicella et al. 2012; Gerkey 2013; Lamba & Mace 2011; Næss et al. 2010

Who do herders help?

What makes people more likely to receive gifts?

Hypotheses:

Genetic kinship > cultural kinship gifts to relatives

Cultural kinship > genetic kinship gifts to cooperative group

Wealth flows: gifts given to younger family members

Kaplan 1994; Hamilton 1964; Trivers 1971

Study site: Finnmark, Norway

~3,500 Saami reindeer herders

533 license owners

(75 in study district)

Saami reindeer husbandry

Households form cooperative groups: the siida

Summer siidas contain from 10 to 100+ people

Summer siidas split into smaller, family-oriented winter siidas

70°

65°

60°

20°10°

100 km

From Næss (2009)

Interviewed 30 (out of 75) licensed herd owners in a district

Externally valid, culturally salient experimental game: anonymous gifts of petrol

Assembled complete kinship network for district

Methods

Results

Colours are siidas

Circles = 75 license owners(Size is no. gifts received)

Gift network

Gift network

Colours are siidas

Circles = 75 license owners(Size is no. gifts received)

Filled circle = 30 interviewees

Gift network: 71 gifts given. 45 given within siida.

Colours are siidas

Circles = 75 license owners(Size is no. gifts received)

Filled circle = 30 interviewees

Lines = gifts(Thickness is gift size)

Breakdown of gifts:

Same siida? Related?Gift?Yes

YesYes 30

No 15

NoYes 3

No 23

Same siida? Related?Gift?

Yes No

YesYes 30 74

No 15 153

NoYes 3 88

No 23 1,834

Breakdown of gifts:Highest proportion given to kin in same siida

Total of 2,220 potential giftsgiven from 30 interviewees

to any of 75 people

Yes

No

Yes

No

Yes

No

Yes

No

Most of the 23 gifts to non-kin in other siidas are for ‘good’ or new herders

Good herders: 8

Young/new owners: 5

Current or future reciprocity: 2

Old friend: 1

Need help: 1

Lazy: 3

Family: 2

(No reason given): 1

Siida membership is strongest predictor of receiving a gift

(the best model)

Model Predictors Odds ratio p value ΔAIC

Close family onlyMember of same summer siida? (ref: no) 24.29 0.004

0.000Close family ( )? (ref: no) 6.05 0.24

All relativesMember of same summer siida? (ref: no) 19.11 <0.001

1.006Genetic relative ( )? (ref: no) 4.66 0.068

Gifts not preferentially given to younger family

Gifts to kin Gifts to non-kin

to youngerherders

to olderherders

to youngerherders

to olderherders

Siida membership makes people more likely to receive gifts

Hypotheses:

Genetic kinship > cultural kinship gifts to relatives

Cultural kinship > genetic kinship gifts to cooperative group

Wealth flows: gifts not given to younger family members

Belonging to the same siida is strongest predictor of receiving gifts

But gifts given to non-kin in other siidas- reputation and reciprocity

No age bias in gift giving

Studies of cooperation to understand high reindeer death rate

Summary

Ruth MaceAndrea MiglianoHuman Evolution Ecology Group at UCL

Katharina OlsenJon Mikkel EiraThe herders of Finnmark

ERCFramsenteretNorsk Institutt for NaturforskningCICERO

Thanks

ReferencesAktipis, C. A., Cronk, L., & Aguiar, R. (2011). Risk-Pooling and Herd Survival: An Agent-Based Model of a Maasai Gift-Giving System. Human Ecology, 39, 131–140

Apicella, C. L., Marlowe, F. W., Fowler, J. H., & Christakis, N. A. (2012). Social networks and cooperation in hunter-gatherers. Nature, 481, 497–501

Gerkey, D. (2013). Cooperation in context: Public goods games and post-Soviet collectives in Kamchatka, Russia. Current Anthropology, 54, 144–176

Lamba, S., & Mace, R. (2011). Demography and ecology drive variation in cooperation across human populations. Proceedings of the National Academy of Sciences of the United States of America, 108, 14426–30

Næss, M. W., Bårdsen, B.-J., Fauchald, P., & Tveraa, T. (2010). Cooperative pastoral production — the importance of kinship. Evolution and Human Behavior, 31, 246–258

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Trivers, R. (1971). The evolution of reciprocal altruism. Quarterly Review of Biology, 46, 35–57

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