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Human Nature

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Does Kin-Selection Theory Help to Explain Support Networks among Farmers in South-Central Ethiopia?

  • Lucie ClechEmail author
  • Ashley Hazel
  • Mhairi A. Gibson
Article

Abstract

Social support networks play a key role in human livelihood security, especially in vulnerable communities. Here we explore how evolutionary ideas of kin selection and intrahousehold resource competition can explain individual variation in daily support network size and composition in a south-central Ethiopian agricultural community. We consider both domestic and agricultural help across two generations with different wealth-transfer norms that yield different contexts for sibling competition. For farmers who inherited land rights from family, firstborns were more likely to report daily support from parents and to have larger nonparental kin networks (n = 180). Compared with other farmers, firstborns were also more likely to reciprocate their parents’ support, and to help nonparental kin without reciprocity. For farmers who received land rights from the government (n = 151), middle-born farmers reported more nonparental kin in their support networks compared with other farmers; nonreciprocal interactions were particularly common in both directions. This suggests a diversification of adult support networks to nonparental kin, possibly in response to a long-term parental investment disadvantage of being middle-born sons. In all instances, regardless of inheritance, lastborn farmers were the most disadvantaged in terms of kin support. Overall, we found that nonreciprocal interactions among farmers followed kin selection predictions. Direct reciprocity explained a substantial part of the support received from kin, suggesting the importance of the combined effects of kin selection and reciprocity for investment from kin.

Keywords

Support network Social capital Birth order Kin selection Reciprocity Inequalities 

Notes

Acknowledgments

This work was funded by a Leverhulme Trust Research Grant F/00182/BI. Logistical support was provided in part by the Centre Français d’Etude Ethiopienne. We are particularly grateful to the people of the Hitoya and Tiyo districts, Arsi zone, Oromia region, for their warm welcome and for facilitating this research. We thank the field team for many months of hard work in the field on data collection. Suggestions provided by James Holland Jones, Aurelie Cailleau, and Sid Karunaratne are greatly appreciated. Finally, we thank the anonymous reviewers for their helpful comments and feedback.

Supplementary material

12110_2019_9352_MOESM1_ESM.docx (30 kb)
ESM 1 (DOCX 29.9 kb)
12110_2019_9352_MOESM2_ESM.xlsx (65 kb)
ESM 2 (XLSX 65.3 kb)

References

  1. Aldrich, D. (2012). Building resilience: Social capital in post disaster recovery. Chicago: University of Chicago Press.CrossRefGoogle Scholar
  2. Aldrich, D., & Meyer, M. (2014). Social capital and community resilience. American Behavioral Scientist, 59, 254–269.  https://doi.org/10.1177/0002764214550299.CrossRefGoogle Scholar
  3. Allen-Arave, W., Gurven, M., & Hill, K. (2008). Reciprocal altruism, rather than kin selection, maintains nepotistic food transfers on an Ache reservation. Evolution and Human Behavior, 29, 305–318.CrossRefGoogle Scholar
  4. Alvergne, A., Lawson, D., Clarke, P., Gurmu, E., & Mace, R. (2012). Fertility, parental investment, and the early adoption of modern contraception in rural Ethiopia. American Journal of Human Biology., 25(1), 107–115.CrossRefGoogle Scholar
  5. Bernard, H. (2002). Research methods in anthropology: Qualitative and quantitative approaches, fifth edition. Lanham, MD: Rowman & Littlefield.Google Scholar
  6. Boone, J. (1986). Parental investment and elite family structure in preindustrial states: A case study of late medieval–early modern Portuguese genealogies. American Anthropologist, 88(4), 859–878.CrossRefGoogle Scholar
  7. Boone, J. (1992). Competition, conflict, and the development of social hierarchies. In E. Smith & B. Winterhalder (Eds.), Evolutionary ecology and human behavior (pp. 301–337). Hawthorne: Aldine de Gruyter.Google Scholar
  8. Carter, G., & Wilkinson, G. (2013). Food sharing in vampire bats: Reciprocal help predicts donations more than relatedness or harassment. Proceedings of the Royal Society, 280, 20122573.  https://doi.org/10.1098/rspb.2012.2573.CrossRefGoogle Scholar
  9. Caudell, M., Rotolo, T., & Grima, M. (2015). Informal lending networks in rural Ethiopia. Social Networks, 40, 34–42.CrossRefGoogle Scholar
  10. Clarke, A., & Low, B. (1992). Ecological correlates of human dispersal in 19th century Sweden. Animal Behaviour, 44, 677–693.CrossRefGoogle Scholar
  11. Clutton-Brock, T. (1984). Reproductive effort and terminal investment in iteroparous animals. The American Naturalist, 123(2), 212–229.CrossRefGoogle Scholar
  12. Clutton-Brock, T. (2009). Cooperation between non-kin in animal societies. Nature, 462(7269), 51–57.CrossRefGoogle Scholar
  13. Congdon Fors, H., Houngbedji, K., & Lindskog, L. (2019). Land certification and schooling in rural Ethiopia. World Development, 115, 190–208.CrossRefGoogle Scholar
  14. Draper, P., & Hames, R. (2000). Birth order, sibling investment, and fertility among Ju/'hoansi (!Kung). Human Nature, 11(2), 117–156.CrossRefGoogle Scholar
  15. Dunbar, R. (2008). Cognitive constraints on the structure and dynamics of social networks. Group Dynamics: Theory, Research, and Practice, 12(1), 7–16.CrossRefGoogle Scholar
  16. Dunbar, R., & Spoors, M. (1995). Social networks, support cliques, and kinship. Human Nature, 6(3), 273–290.CrossRefGoogle Scholar
  17. Fafchamps, M., & Lund, S. (2003). Risk-sharing networks in rural Philippines. Journal of Development Economics, 71(2), 261–287.CrossRefGoogle Scholar
  18. Faurie, C., Russell, A., & Lummaa, V. (2009). Middleborns disadvantaged? Testing birth-order effects on fitness in pre-industrial Finns. PLoS One, 4(5), 56–80.CrossRefGoogle Scholar
  19. Fowler, F. (1995). Improving survey questions: design and evaluation. Applied Social Research Series 38. Thousand Oaks: Sage.Google Scholar
  20. Gavian, S., & Ehui, S. (1999). Measuring the production efficiency of alternative land tenure contracts in a mixed crop-livestock system in Ethiopia. Agricultural Economics, 20, 37–49.CrossRefGoogle Scholar
  21. Gibson, M. (2002). Development and demographic change: The reproductive ecology of a rural Ethiopian Oromo population. PhD thesis, University College London.Google Scholar
  22. Gibson, M., & Gurmu, E. (2011). Land inheritance establishes sibling competition for marriage and reproduction in rural Ethiopia. Proceedings of the National Academy of Sciences (USA), 108(6), 2200–2204.CrossRefGoogle Scholar
  23. Gibson, M., & Gurmu, E. (2012). Rural to urban migration is an unforeseen impact of development intervention in Ethiopia. PLoS One, 7(11), e48708.  https://doi.org/10.1371/journal.pone.0048708.CrossRefGoogle Scholar
  24. Gibson, M., & Lawson, D. (2011). Modernization increases parental investment and sibling resource competition: Evidence from a rural development initiative in Ethiopia. Evolution and Human Behavior, 32, 97–105.CrossRefGoogle Scholar
  25. Gibson, M., & Sear, R. (2010). Does wealth increase parental investment biases in child education? Evidence from two African populations on the cusp of the fertility transition. Current Anthropology, 51, 693–701.CrossRefGoogle Scholar
  26. Gurven, M., Hill, K., Kaplan, H., Hurtado, A., & Lyles, R. (2000). Food transfers among Hiwi foragers of Venezuela: Tests of reciprocity. Human Ecology, 28(2), 171–218.CrossRefGoogle Scholar
  27. Hames, R. (1987). Garden labor exchange among the Ye’kwana. Ethology and Sociobiology, 8(4), 259–284.CrossRefGoogle Scholar
  28. Hamilton, W. (1964). The genetical evolution of social behaviour. Journal of Theoretical Biology, 7(1), 1–16.CrossRefGoogle Scholar
  29. Hamilton, M., Milne, B., Walker, R., Burger, O., & Brown, J. (2007). The complex structure of hunter-gatherer social networks. Proceedings of the Royal Society, 274, 2195–2203.  https://doi.org/10.1098/rspb.2007.0564.CrossRefGoogle Scholar
  30. Hertwig, R., Davis, J., & Sulloway, F. (2002). Parental investment: How an equity motive can produce inequality. Psychological Bulletin, 128(5), 728–745.CrossRefGoogle Scholar
  31. Hill, R., & Dunbar, R. (2003). Social network size in humans. Human Nature., 14(1), 53–72.CrossRefGoogle Scholar
  32. Hrdy, S., & Judge, D. (1993). Darwin and the puzzle of primogeniture. Human Nature, 4(1), 1–45.CrossRefGoogle Scholar
  33. Jaeggi, A., & Gurven, M. (2013). Reciprocity explains food sharing in humans and other primates independent of kin selection and tolerated scrounging: A phylogenetic meta-analysis. Proceedings of the Royal Society B, 280, 20131615.  https://doi.org/10.1098/rspb.2013.1615.CrossRefGoogle Scholar
  34. Judge, D., & Hrdy, S. (1992). Allocation of accumulated resources among close kin: Inheritance in Sacramento, California, 1890-1984. Ethology and Sociobiology, 13, 495–522.CrossRefGoogle Scholar
  35. Kidwell, J. (1982). The neglected birth order: Middleborns. Journal of Marriage and Family, 44(1), 225–235.CrossRefGoogle Scholar
  36. Krosnick, J., & Fabrigar, L. (1997). Designing rating scales for effective measurement in surveys. In L. Lyberg, P. Biemer, M. Collins, E. De Leeuw, C. Dippo, N. Schwarz, & D. Trewin (Eds.), Survey measurement and process quality (pp. 141–164). Wiley Series in Probability and Statistics. New York: Wiley.Google Scholar
  37. Lewis, J. (2010). Connecting and cooperating: Social capital and public policy. Sydney: University of New South Wales Press.Google Scholar
  38. Narayan, D., & Pritchett, L. (1999). Cents and sociability: Household income and social capital in rural Tanzania. Economic Development and Cultural Change, 47(4), 871–897.CrossRefGoogle Scholar
  39. Patton, J. (2005). Meat sharing for coalitional support. Evolution and Human Behavior, 26, 137–157.CrossRefGoogle Scholar
  40. Pollet, T., & Nettle, D. (2007). Birth order and face-to-face contact with a sibling: Firstborns have more contact than laterborns. Personality and Individual Differences, 43, 1796–1806.CrossRefGoogle Scholar
  41. Pollet, T., & Nettle, D. (2009). Birth order and adult family relationships: Firstborns have better sibling relationships than laterborns. Journal of Social and Personal Relationships, 26(8), 1029–1046.CrossRefGoogle Scholar
  42. Pretty, J. (2003). Social capital and the collective management of resources. Science, 302, 1912–1914.CrossRefGoogle Scholar
  43. Putnam, R. (2000). Bowling alone: America’s declining social capital. In L. Crothers & C. Lockhart (Eds.), Culture and politics (pp. 223–234). New York: Palgrave Macmillan.Google Scholar
  44. Rohde, P., Atzwanger, K., Butovskaya, M., Lampert, A., Mysterud, I., Sanchez-Andres, A., & Sulloway, F. (2003). Perceived parental favoritism, closeness to kin, and the rebel of the family: The effects of birth order and sex. Evolution and Human Behavior, 24, 261–276.CrossRefGoogle Scholar
  45. Salmon, C. (2003). Birth order and relationships. Human Nature, 14(1), 73–88.CrossRefGoogle Scholar
  46. Salmon, C., & Daly, M. (1998). Birth order and familial sentiment: Middleborns are different. Evolution and Human Behavior, 19, 299–312.CrossRefGoogle Scholar
  47. Santos, P., & Barrett, C. (2006). Informal insurance in the presence of poverty traps: Evidence from southern Ethiopia. Ithaca: Cornell University Working Paper.Google Scholar
  48. Smith, E., Borgerhoff Mulder, M., Bowles, S., Gurven, M., Hertz, T., & Shenk, M. (2010). Production systems, inheritance, and inequality in premodern societies: Conclusions. Current Anthropology, 51(1), 85–94.CrossRefGoogle Scholar
  49. Stanton, M. A., Lonsdorf, E. V., Pusey, A. E., Goodall, J., & Murray, C. M. (2014). Maternal behavior by birth order in wild chimpanzees Pan troglodytes increased investment by first-time mothers. Current Anthropology, 55(4), 483–489.CrossRefGoogle Scholar
  50. Strassman, B., & Clarke, A. (1998). Ecological constraints on marriage in rural Ireland. Evolution and Human Behavior, 19, 33–55.CrossRefGoogle Scholar
  51. Sulloway, F. (1996). Born to rebel: Birth order, family dynamics, and creative lives. New York: Pantheon Books.Google Scholar
  52. Taborsky, M. (2013). Social evolution: Reciprocity there is. Current Biology, 23, R486–R488.CrossRefGoogle Scholar
  53. Tefera, B., Ayele, G., Yigezu, A., Jabbar, M., & Dubale, P. (2002). Nature and causes of land degradation in the Oromiya region: A review. Socio-economics and Policy Research Working Paper 36. Nairobi: International Livestock Research Institute.Google Scholar
  54. Towner, M. (2001). Linking dispersal and resources in humans: Life history from Oakham, Massachusetts (1750-1850). Human Nature, 12(4), 321–349.CrossRefGoogle Scholar
  55. Trivers, R. (1971). The evolution of reciprocal altruism. The Quarterly Review of Biology, 46(1), 35–57.CrossRefGoogle Scholar
  56. Trivers, R. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the descent of man, 1871–1971 (pp. 136–179). Chicago: Aldine.Google Scholar
  57. Trivers, R. (1974). Parent-offspring conflict. American Zoologist, 14(1), 249–264.CrossRefGoogle Scholar
  58. Trivers, R., & Willard, D. (1973). Natural selection of parental ability to vary the sex ratio of offspring. Science, 179(4068), 90–92.CrossRefGoogle Scholar
  59. Voland, E., & Dunbar, R. (1995). Resource competition and reproduction, the relationship between economic and parental strategies in the Krumhorn population (1720-1874). Human Nature, 6(1), 33–49.CrossRefGoogle Scholar
  60. Zhou, W., Sornette, D., Hill, R., & Dunbar, R. (2005). Discrete hierarchical organization of social group sizes. Proceedings of the Royal Society B: Biological Sciences, 272(1561), 439–444.CrossRefGoogle Scholar

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Authors and Affiliations

  1. 1.Department of Anthropology and ArchaeologyUniversity of BristolBristolUK
  2. 2.Department of AnthropologyStanford UniversityStanfordUSA
  3. 3.Department of Earth System ScienceStanford UniversityStanfordUSA

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