Data were collected in four separate years – usually during the dry season – over a six-year period (2010, Aug/Sept; 2013, July; 2014, Oct/Nov; 2016, Aug/Sept). Data collection was supervised by different authors in different years: (CLA in 2010, 2013; IM in 2014 and KMS in 2016). In 2014 and 2016 Tanzanian researchers blind to the hypotheses collected the data. In each year, camps were visited using a technique not unlike snowball sampling. After establishing contact with the first camp, Hadza would direct the researchers to the next nearest camp. GPS coordinates were recorded for all camps in each year, with the exception of 2016 when the GPS receiver met an unfortunate end. Nevertheless, we were able to divide the camps in 2016 into market and nonmarket groups based on their general proximity to the village ( Figure 1 ).

Public Goods Game

34 Jaeggi A.V.

van Schaik C.P. The evolution of food sharing in primates. 35 Kaplan H.

Gurven M. The natural history of human food sharing and cooperation. 36 Kaplan H.

Hill K.

Cadelina R.V.

Hayden B.

Hyndman D.C.

Preston R.J.

Smith E.A.

Stuart D.E.

Yesner D.R. Food sharing among Ache Foragers. 4 Apicella C.L.

Marlowe F.W.

Fowler J.H.

Christakis N.A. Social networks and cooperation in hunter-gatherers. We used a public goods game as our measure of cooperation. This game is directly applicable to hunter-gatherer life where collective action problems are faced by groups on a daily basis. We used a food item instead of money since explanations for the evolution of cooperation have highlighted the importance of food sharing []. The methods for the public goods game elicitation in the Hadza has been described previously [].

Cooperation was elicited by examining participants’ voluntary contributions in a public goods game played with adult members of their camp. All games were conducted in Swahili and inside a vehicle for privacy. All adults in each camp were invited to participate with the exception of the very elderly and infirm. In 2010, 2013 and 2014 the game was played on the last day the researcher was in camp in order to limit possible discussion. Participants were also told that the game was secret. Since decisions were made in private, any assertions made by participants regarding their decision need not be truthful. In 2016, the game was played throughout the researcher’s stay in the camp. Importantly, we find the same pattern of results.

37 Berbesque J.C.

Marlowe F. Sex differences in food preferences of Hadza hunter-gatherers. Participants were endowed with four straws of 100% pure honey (2010, Honeystix, GloryBee foods 2013, 2014, Honey Stix, Stakich), a prized food of the Hadza []. Each honey stick contains roughly 15 calories. Participants then faced the decision of how to divide their honey sticks into a private account and a public account. Participants were told that the goods would be distributed evenly with all other adult camp members who also played the game. They were instructed that they could keep any amount from 0-4 sticks of the honey or donate them to the public goods by inserting them into an opaque cardboard box with an opening at the top. Subjects were told that for every stick of honey they donated, the researcher would donate an additional 3 sticks of honey to the public pot, and that, after all adult campmates played the game, the honey would be divided equally among them. Participants were also told that they would receive their undonated honey at the same time as the public honey was distributed to avoid confounding generosity with patience. Before subjects made their decision, the researcher simulated all their possible choices so that subjects were shown the additional amount of honey added to the box for each decision.

38 Apicella C.L.

Azevedo E.M.

Christakis N.A.

Fowler J.H. Evolutionary origins of the endowment effect: Evidence from hunter-gatherers. 39 Henrich J.

Boyd R.

Bowles S.

Camerer C.

Fehr E.

Gintis H.

Mcelreath R. Cooperation, reciprocity, and punishment in fifteen small-scale societies. 40 Henrich J.

Mcelreath R.

Barr A.

Ensminger J.

Barrett H.C.

Bolyanatz A.

Cardenas J.C.

Gurven M.

Gwako E.

Henrich N.

et al. Costly punishment across human societies. 41 Marlowe F.W. Dictators and ultimatums in an egalitarian society of hunter-gatherers: The Hadza of Tanzania. The Hadza have had experience playing various games to measure economic (e.g., endowment effect and risk) and social preferences (e.g., dictator, ultimatum, third-party punishment) with researchers over the last decade [].

This is the basic script used each year in both English and Swahili.

English We are playing a game with honey. This game is voluntary. You do not have to play this game. You will not be punished if you choose not to play. This study is a secret. I will not tell anyone the decision you make. Also, I will not tell you the decision that anyone else makes. All adults living in your camp will have the opportunity to play this game. This game involves honey (show them 4 honey sticks). Inside these sticks is honey to eat. The decisions you make and the decisions other people make will affect how much honey you get and how much honey your other camp members get. You will only receive your share of honey after everyone has had a chance to the play the game. Any honey you receive will be given to you in secret, and nobody will see how much honey you get. • keep all of the sticks of honey

• keep 3 of the sticks

• keep 2 of the sticks

• keep1 stick

• keep zero sticks. Here are 4 sticks of honey (hand it to them). You need to choose how many sticks to keep and how many sticks to put inside this box. You can choose to: • If you put in 1 stick, I will add 3 sticks.

• If you put in 2 sticks, I will add 6 sticks.

• If you put in 3 sticks, I will add 9 sticks.

• If you put in 4 sticks, I will add 12 sticks.

• If you keep all 4 honey sticks for yourself, I will not add any honey to the box.

• If everyone puts honey in the box, then the box will fill up and everyone will get a lot more honey. If no one or only a few people put honey in the box, then there will be very little honey to share. No one will know how many sticks you choose to keep. Any honey that you do not keep will be put in this box and shared equally with all the people who played this game, including yourself. For every stick of honey you put in this box, I will add 3 sticks.

Swahili Tunaenda kucheza mchezo wa asali. Mchezo huu ni hiari. Unaweza kuamua usicheze mchezo huu. Hautaadhibiwa kama utaamua kutocheza. Somo hili ni siri. Sitamwambia mtu yeyote maamuzi utakayofanya. Pia, sitakwambia maamuzi ambayo mwingine amefanya. Watu wazima wote wanaoishi kwenye kambi yako watakuwa na nafasi ya kucheza mchezo huu. Mchezo huu unahusisha asali (waoneshe fimbo 4 za asali). Ndani ya fimbo hizi ni asali unaweza kuila. Maamuzi ambayo unafanya na maamuzi ambayo watu wengine wanafanya yanaathiri jinsi wewe unavyopata asali na watu wengine pia kambini. Utapata tu sehemu yako ya asali baada ya kila mtu kupata nafasi ya kucheza mchezo. Na asali utakayopata utapewa kwa siri na hakuna yeyote atakayeona umepata asali ngapi. Hizi ni fimbo 4 za asali (mkabidhi). Unatakiwa uchague ni fimbo asali ngapi ubakiwe nazo na asali ngapi uweke ndani ya boksi hili. Unaweza kuchagua: • Kubakiwa na fimbo 3

• Kubakiwa na fimbo 2

• Kubakiwa na fimbo 1

• Kutobakiwa na fimbo, sifuri

• Hakuna mtu ambaye atajua umeamua kubakiwa na fimbo ngapi

• Na asali yeyote ambayo hutobakiwa nayo itawekwa ndani ya boksi hili na zitagawanywa sawa kwa sawa na kila mtu ambaye amecheza mchezo huu, ukiwemo wewe

• Kwa kila fimbo ya asali utakayoweka ndani ya boksi hili, nitaongeza fimbo 3.

• Ukiweka fimbo 1, nitaongeza fimbo 3

• Ukiweka fimbo 2, nitaongeza fimbo 6

• Ukiweka fimbo 3, nitaongeza fimbo 9

• Ukiweka fimbo 4, nitaongeza fimbo 12

• Kama utabakiwa na fimbo zote 4 za asali kwa ajili yako, sitaongeza asali yeyote ndani ya boksi

• Kama kila mtu ataweka asali kwenye boksi, hivyo boksi litajaa na kila mtu atapata asali nyingi sana. Kama hakuna mtu au watu wachache wataweka asali kwenye boksi, kutakuwa na asali kidogo sana za kugawana/shirikiana Kubakiwa na fimbo zote za asali