Approach to Resource Management and Physical Strength Predict Differences in Helping: Evidence From Two Small-Scale Societies

Helping behavior is likely to have evolved to increase chances of survival of an individual and their group. Nevertheless, populations differ significantly in their eagerness to help, and little is known about populational and inter-individual determinants of these differences. Previous studies indicated that economic and physiological factors might influence helping behavior. The aim of the present study was to investigate the effects of approach to resource management of a society (immediate-return economy vs. delayed-return economy), prenatal androgenization (based on second-to-fourth digit ratio), and physical strength (based on hand grip strength) on helping behavior toward others. Helping was assessed in terms of both general eagerness to help and differential helping toward: (1) kin, (2) other group members indiscriminately, (3) friends, and (4) those from whom help was obtained in the past. Based on data collected in two small-scale societies (n = 306), we found that people in the egalitarian immediate-return society (the Hadza hunter-gatherers of Tanzania) displayed helping behavior significantly more often than people in a more stratified delayed-return economy (Yali horticulturalists of Papua). Additionally, our results revealed that physical strength was a significant predictor of helping behavior in women but not in men. We discuss our findings in the light of the adaptive value of helping behavior.

Trolley Dilemma in Papua. Yali horticulturalists refuse to pull the lever

Although many studies show cultural or ecological variability in moral judgments, cross-cultural responses to the trolley problem (kill one person to save five others) indicate that certain moral principles might be prevalent in human populations. We conducted a study in a traditional, indigenous, non-Western society inhabiting the remote Yalimo valley in Papua, Indonesia. We modified the original trolley dilemma to produce an ecologically valid "falling tree dilemma." Our experiment showed that the Yali are significantly less willing than Western people to sacrifice one person to save five others in this moral dilemma. The results indicate that utilitarian moral judgments to the trolley dilemma might be less widespread than previously supposed. On the contrary, they are likely to be mediated by sociocultural factors.

Transformation of tobacco plants by Yali PPO-GFP fusion gene and observation of subcellular localization

To explore the subcellular localization of Polyphenol oxidase (PPO) from Pyrus bretschneideri, the 1779 bp cDNA of PPO gene excluding the termination codon TAA was cloned and fused with GFP to construct a binary vector pBI121-PPO-GFP. Then, the binary vector was transformed into Nicotiana tabacum by the tumefanciens-mediated method. Using confocal laser scanning microscopy, green fluorescent signals were localized in chloroplasts of the transformed Nicotiana tabacum cell, suggesting that the Polyphenol oxidase from Pyrus bretschneideri was a chloroplast protein.